Author Topic: [FT] xDevs.com KX LTZ1000A fairy-tale, or the story of little jumper.  (Read 65661 times)

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Offline TiN

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Let's start the new segment, fairy-tales of metrology  :-DD

Intro

One of engineers doing precision measurement projects at home for own enjoyment contacted me while ago, asking some questions related to nanovolt-meter amplifier front-end and voltage references. His country of residence is Belarus, and I mention this because their customs are really strict about international shipments. Basically everything over 20 $USD mark is troublesome to import and due to high fees, often much more than package value itself. So his instrumentation desk was mostly using some old instruments, made in Soviet Union. We had nice talk about electrometer of his, which is an interesting bit of gear on its own.

On DMM front he has Datron Model 1271, 7½-digit DMM, smaller brother of Model 1281 which our other contributor, Todd, had covered well before. Quickly talk was biased towards voltage references. Buying famous Linear LTZ1000 was not an easy option due to shipping/customs troubles, even worse considering existing lack of access to calibrators or metrology labs nearby. Even though this 1271 is fine instrument, it was not recently calibrated and absolute accuracy was unknown. Since this situation was very familiar for me few years ago, I decided to give a hand and help this engineer to “import” verified DCV standard into his home hobby lab. Agreement to build one KX LTZ1000 voltage reference was made.

Buy some parts, put on PCB with less than 30 components, measure the output and send the board thru mail. Sounds easy job, no rocket science, right?

Parts source and assembly

To make this whole little project more interesting for me, I wanted to try two new ideas, which were not attempted before in previous builds.

*A.* Try 1K?/13K? hermetic resistor network (custom Vishay VHD200, oil-filled +/-3ppm/K two-resistor network) with 0.05% matching. This might give some interesting data, if tightly coupled oven setting thermal point resistors help to improve tempco of the reference.

*B.* Try alternative chopper amplifier, Analog Devices ADA4522-1. Usually I use LTC2057, but both op-amps are rather overkill for this particular circuit, as noise of LTZ1000 zeners itself is magnitudes higher than opamp contribution. But maybe other issues pop up with AD chip. Let's see.


As a base my latest Rev.B02 version of KX LTZ1000 PCB is used. This module 4-layer FR4 ENIG-plated PCB use two single op-amps in SO-8 package, accepts +10-20VDC input


Before soldering resistors down into circuit, I did a quick measurement to check that they don't give some wild deviations.

Custom VPG 120 ?, R3 , -0.8 ppm - +26.4 C, 0.36 ppm/K
VPG VHD200 1 K?, R4 , -75 ppm - +24.0 C   2.5 ppm/K
VPG VHD200 13 K?, R5 , -5 ppm - +24.3 C   1.4ppm/K


First small SMD parts were soldered on, and checked. Used LTZ1000ACH chip, manufactured 36 week of 1993 was soldered on, with maximum soldering time around 0.5 second per pin, to reduce excessive heating. Foil precision resistors were populated last. Assembled module ready for the initial test.


Before we jump in to actual test data, it's important to have good confidence in measurement equipment and lab tools, to make sure that any unexpected phenomenon comes from device under test, not the equipment itself. This also means that even brand new, freshly calibrated equipment must be verified and tested before any solid conclusions to be made.

To satisfy this requirement, I had chance to calibrate my older LTZ1000ACH/LTZ1000CH based references against 15-day calibrated Fluke 732B DC Voltage standard in mid-August 2016. Two Keithley 2002 8.5-digit multimeters we calibrated to same Fluke reference same time, to act as transfer standards and guard-banding tools. I used these DIY standards and DMMs to transfer absolute DCV voltage into my verified and improved HP 3458A, which confirmed to be stable by daily 24/7 operation and monthly checks to both hot and cold external LTZ1000A modules. As a result, I have high confidence that absolute DCV accuracy in my home lab is within +/-2 ppm.

Now with verified gear, initial test conditions are fairly simple. Purpose of first test is to make sure of reference normal operation, and measure initial voltage, drift if any and stability. Output should not deviate more than +/-1 ppm over few days period, and temperature coefficient (change of output voltage from change of ambient temperature) should not exceed +/- 0.1 ppm/K.

Power supply : 12VDC 2A cheap mains power brick.
Measurement  : HP 3458A, calibrated August 31 to +/-2ppm DCV.
Ambient condition : Ambient room temp with aircon, +/-3 C. Monitor by BME280 sensor
Datalogging : Raspberry Pi with linux-gpib + python + NI GPIB-USB-HS
Analysis : D3.js plotting library on xDevs.com site

Test 1


Yes, it's alive, measuring output voltage +7.067329 VDC +/-2 ppm.

And how we looking here? If this would be integrated reference, such as band-gap reference on internal DAC/ADC references, result noise 1.1 ppm could be simply miraculous. However for top-end ovenized buried zeners, which for Linear LTZ1000 is extremely bad. To remind you specifications, this circuit should be able to provide 0.05 ppm/K drift rate and approximate noise levels of 1.2 uVpk-pk. We are getting 7.4 uV instead for noise. Tempco is also horrible, about 1 ppm/K, 20 times worse than expected!

Test 2: TC correction resistor add

For second test we work on mistake and try to address issues on data we saw earlier.

* Improve stability of ambient temperature, so we can isolate TC issue for now.
* Test with 394K R2 populated, even though we use LTZ1000ACH and this compensation not needed.


Some of our readers not familiar with LTZ1000 performance may scream at me right now, how you know that this is bad result. Vertical ppm scale (left green scale is +/-1ppm, which is 0.0001% accuracy!) is blown out to make this amazing reference look bad, you say?

Alright, I hear you. And here's the answer, same condition measurements with good and checked LTZ1000CH voltage reference module, using same schematic and same PCB, just different parts. Horizontal time span of graph below is 11 hours.


Reference test result on another LTZ1000CH KX module

See, noise of this good module is mere +/-0.1ppm, no random jumps or other weird crap, everything nice and stable. That's how you want it, not jumpy-jumpy . Of course if you reduce your accuracy demands to 0.002%, everything looks nice even with jumps.


But it does not make sense to pay 250$ USD for such accuracy, so let's continue our journey.

Test 3: Reduction of oven temperature test

Alright, how about reduce LTZ1000ACH oven temperature inside chip, by changing 13K? resistance on divider to lower value? Let's see

Fluke 300K? -1 ppm/K wirewound resistor was soldered in parallel with 13K? on board, and test was repeated.


Test 4: Op-amp kelvin connection test

Here I had cut separate trace between Pin 2 U5 opamp and R6 resistor, and jump-wired connected guard ring point directly at pin 4 of LTZ1000ACH chip. This makes almost Kelvin-like connection for all inverting node connections. Why I did so? Hm, intuition? :)


Jumpie-jumpie is still there. Noise of LTZ chip noise itself is riding on top of those jumps. Overall it looks nice and stable, just the pesky jumps, which is pink-noise of zener junction. Output voltage changed from +7.064808 to +7.066329 VDC, which is +215 ppm.

Test 5: Replacement of LTZ1000 chip

Now, if we dig a bit into physics, this jumps are nothing but pink-noise, likely caused by zener effect breakdown is due to quick bursts of electrons going thru thin junction on high voltage. This breakdown is just about 7 volts, and that's close to out near 7.06V output of zener inside this LTZ1000ACH. So it does look that no external component tweaks could fix this... Let's see on test result of TEST RUN 5:


t's good now! What is the magic? There is none, actually, just engineering. Now we getting some solid data. Noise over multiple hours is just around 0.2ppm, which translates into around 1.2 uV[~pk-pk~], initial tempco evaluation from +26.6  C to +30.5  C unable to reveal any tempco clearly, no large jumps either.

Bonus

I also built thermal box to test tempco, so jump into full article link down below :)


Total amount of time for this project ~25 hours, including ~50 hours of datalog time by HP 3458A.

Hope this data helps to better understand hidden icebergs and dangers big enough to sink a project in high-precision field, even for something as simple as direct voltage reference module. It's not enough to buy fancy parts and plonk them on the board to get 1 ppm accuracy.

I have it running tempco test now, from 20C to 55C in 0.1C per hour step.

Full article

If you have own unexpected story, do tell us.  :popcorn:

Important update, calibration offer by community

One of our members, mimmus78 ordered KX LTZ1000 PCBs and sent some to other interested tinkerers at cost, so to support this great initiative, additional "calibration service" is provided by me, plesa and Alex Nikitin to support this.

Rules to participate are simple:

STEP 1. Build your KX-module, publish short worklog in this thread (few photos of assembled PCBA, photo of it running with DMM hooked up showing 7V)
STEP 2. Leave it running for 200 hours, so initial drifts get stabilized. Module should be enclosed in some box without vents.
STEP 3. Measure it again, record the temperature and voltage and put a label with values on the box
STEP 4. Ship the box to me (Taiwan) or other member (Europe) after agreement via EEVBlog PM. You pay shipping.
STEP 5. I'll power your box with +15V for 48 hours to have everything stabilize
STEP 6. Test 7V output voltage in temperature span +20....+30C, record the graph
STEP 7. Unit will be shipped back (from me via EMS Express (~30-40$USD, 4-7 days to USA, bit more to EU)). You pay shipping.

All steps are mandatory, to make sure that reference is good and stable, otherwise it would be no much point in ppm-level calibration, if initial aging drifts are not removed first.
This is standing offer, without schedule or specific date deadlines, unless my homelab changes or other force majeure events occur.

Even though I don't have official calibration performed on my equipment, thanks to volt-nut community and multiple cross-checks I'm confident that my DCV accuracy is around ±2 ppm.
And to make this even better, few other EEVBlog members also backed up this initiative to provide same calibration offer in their regions.

Calibration by Accuracy / Standard    Region/Country Contact for participants
  xDevs.com        <2ppm / 3458A-mod + 2*K2002 Asia/Taiwan      EEVBlog forum PM
  plesa            <4ppm / 3458A-002   Europe/Sweden    EEVBlog forum PM 
  Alex Nikitin      <4ppm / 3458A-002   Europe/UK        EEVBlog forum PM

Article was also updated for same information
« Last Edit: April 01, 2017, 05:32:51 pm by TiN »
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Offline lukier

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #1 on: October 18, 2016, 07:15:13 pm »
Interesting story.

I would thought that such expensive parts go through rather stricter testing (than TL431 for example). I remember in your 3458A article the original reference board from eBay also had jumpy LTZ1000.

Is this jumpy LTZ1000 brand new or second hand from eBay?

Slightly worrying, as I would like to build a LTZ1000 reference at some point, but no way I'm buying a dozen chips or so to find one working to the specs  :-//
 

Offline Nuno_pt

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #2 on: October 18, 2016, 07:52:01 pm »
This jumpy LTZ was the one from the A9 board that TiN bought on flebay for is 3458.

The resolution is in the full article in TiN's website, he then replace the LTZ with another one and no more jumps.
Nuno
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #3 on: October 18, 2016, 08:08:17 pm »
lukier

I think you get answers from article ;). If it's more comforting, all 6 LTZ chips I bought directly from Linear site are not jumpy.  :phew:
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Offline Nuno_pt

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #4 on: October 18, 2016, 08:19:05 pm »

To make this whole little project more interesting for me, I wanted to try two new ideas, which were not attempted before in previous builds.

*A.* Try 1K?/13K? hermetic resistor network (custom Vishay VHD200, oil-filled +/-3ppm/K two-resistor network) with 0.05% matching. This might give some interesting data, if tightly coupled oven setting thermal point resistors help to improve tempco of the reference.

TiN do you notice any diference yet, with the exchange of the voltage divider in relation to previous method, of two independent resistors?
This way the tracking of Tempco should be better since they are inside the same encapsulation.

BTW, in a conversation with Edwin Pettis he told me, that the Engineers from LT told him that for the last few years they recommend the all LTZ's to be drive by 15K/1K, but this was already cover in the LTZ thread .
Nuno
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Offline lukier

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #5 on: October 18, 2016, 09:37:48 pm »
I think you get answers from article ;). If it's more comforting, all 6 LTZ chips I bought directly from Linear site are not jumpy.  :phew:

Oh got it :) I thought that's yet another unit, so I worried about LTZ1000 reliability.
 

Offline zlymex

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #6 on: October 18, 2016, 10:47:37 pm »
Good story and nice photos/charts. Slightly worrying for me too because I did not test all of my 2nd hand LTZ1ks fully.

TiN is the thermistor hermetic? It seems to be very stable over time.
 
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #7 on: October 18, 2016, 11:22:38 pm »
zlymex
It's teflon coated. You can see photo of it in the article. Overall it does look more stable than my previously used Honeywell HEL-705 Pt RTDs (on same K2510 setup). I had to increase current for RTD at 833uA compared to just 100uA on this YSI 44031.
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Offline doktor pyta

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #8 on: October 19, 2016, 12:52:44 am »
One time I was repairing Data Precision 8200 DC calibrator.
I did many measurements to prevent good old precision components from heating during soldering.
Unfortunately the problem was LM399 (see plot).
Maybe it is a problem with contact resistance inside IC.
I assume that Data Precision would not release a product with such issue, so it is very likely that this LM399 broke down during normal use.
« Last Edit: October 19, 2016, 12:54:40 am by doktor pyta »
 
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Offline VintageNut

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #9 on: October 19, 2016, 01:04:16 am »
I have been monitoring one of my Fluke 731B for a few days continuously with a DMM7510 on 15 NPLC with averaging of 10. In the morning the measured voltage is 9.999961 and late evening the voltage is 9.999978. This cycle is consistent from day to day. At first I thought it was temperature but after some colder weather followed by warmer weather, I think the cycle is humidity.

I have no humidity measurement equipment now so that has to be on the list to obtain sooner than later.
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline Nuno_pt

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #10 on: October 19, 2016, 01:24:56 am »
For humidity, pressure and temperature I think that the BME280 is hard to beat. And you can do like TiN, sample it together with your measurements via GPIB. 
Nuno
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Offline zlymex

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #11 on: October 19, 2016, 01:41:10 am »
I have been monitoring one of my Fluke 731B for a few days continuously with a DMM7510 on 15 NPLC with averaging of 10. In the morning the measured voltage is 9.999961 and late evening the voltage is 9.999978. This cycle is consistent from day to day. At first I thought it was temperature but after some colder weather followed by warmer weather, I think the cycle is humidity.

Then you need a third equipment to judge, either a DMM or a voltage reference, ^-^
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #12 on: October 19, 2016, 04:15:34 am »
Or send that 7510 to us for check  :=\ 3458 vs 7510... I think that's not equal fight  :box:  :-DMM
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Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #13 on: October 19, 2016, 05:40:43 am »
The Fluke731 and DMM7510 should have a similar class reference inside. So it could be either one that is doing the drift.
The reference in the 3458 is not better than that, and near full scale is could be very well the reference that sets the limitation. So 3458 vs DMM7510 would be LTZ1000 vs LTFLU so this may come down to binning or individual quality.
 

Offline VintageNut

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #14 on: October 19, 2016, 05:57:48 am »
Good points Tin. I will connect my model 2000 in parallel with the 7510 and let it run for a few days to see if the drift is detectable on the 2000 as well.

I am reasonable certain that the drift is the 731B but only proper measurements and analysis of the data will make it certain.

I accept the challenge to find out for sure.

Do you collect your data for this type of analysis with Python?
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #15 on: October 19, 2016, 06:09:31 am »
lukier

I think you get answers from article ;). If it's more comforting, all 6 LTZ chips I bought directly from Linear site are not jumpy.  :phew:

Hello Illya,

You have to look harder on the noise.
My LTZ#5 has relative large jumps of typical 1uV up to 1.8uV.

The others have also jumps (below the 1.2uVpp) which are only visible when zooming into the record.
E.g. LTZ3 with a 300nV jump.

All my LTZs are sourced via distributor or DigiKey.
So even if they are costly you have to monitor them for popcorn noise.
The noise screening tests at the manufacturer typical use a very short time window.
(<< 10 seconds)
So the detection of popcorn noise is usually not possible.

With best regards

Andreas
 

Offline Theboel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #16 on: October 19, 2016, 10:46:21 am »
I am sorry Ilya and others if this not relevant but anybody has experience about same jump/popcorn noise from LM399 ?
 

Offline d-smes

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #17 on: October 19, 2016, 09:32:00 pm »
BTW, in a conversation with Edwin Pettis he told me, that the Engineers from LT told him that for the last few years they recommend the all LTZ's to be drive by 15K/1K, but this was already cover in the LTZ thread .
Is this new info?  I thought you only wanted to run them that hot for the "A" version in high ambient environment.   Can you link to where this recommendation was discussed?  I skimmed through the LTZ1000 thread but couldn't find it...
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #18 on: October 19, 2016, 09:38:52 pm »
The choice is up to application. Lower noise at cost of long term stability - run high temp. Better long term stability (thats what most people here after) at cost of noise - reduced temp.
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #19 on: October 19, 2016, 09:59:20 pm »
Also I realized something this morning during my ride to work.
Since now I have bad, but functional LTZ1000A chip, which I'd not really use in voltage reference builds, it opens a road to second fairy-tale...

We don't really care if it dies, right? Now if I can find LTZ-set resistors which I can sacrifice without breaking a bank, we can make one special module to run cryotest.
That is, enclose module into metal box with weak thermal coupling and submerge everything into fresh 26L dewar with LN2, without heater circuit on.
It could answer question I was asking myself for years, if LTZ1000 at 77K can deliver better than 0.1ppm noise. If it's positive, then that would open new box of pandora making cooled LTZ-references  ^-^.
LN2 is also cheap, so that experiment could be repeated by other volt-nuts if proven worthwhile (for example to do nV LNA testing, when lowest noise possible is a help).

Why need sacrifice resistors? Because they are unlikely to be very good and stable after 230K thermal shock.
« Last Edit: October 19, 2016, 10:01:35 pm by TiN »
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Offline VintageNut

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #20 on: October 19, 2016, 11:02:36 pm »
Have you placed one of these reference boards in an ordinary freezer at 0 deg F to test the idea?
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #21 on: October 19, 2016, 11:32:01 pm »
I'd expect difference at 0 would be just down in measurement errors and uncertainty.
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Offline VintageNut

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #22 on: October 20, 2016, 02:09:14 am »
I'd expect difference at 0 would be just down in measurement errors and uncertainty.

Does the noise reduction only happen at some magic very low temperature or is the noise reduction a linear function of temperature?
working instruments :Keithley 260,261,2750,7708, 2000 (calibrated), 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD, Fluke 731B X2 (calibrated), Fluke 5450A (calibrated)
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #23 on: October 20, 2016, 03:04:42 pm »
Delta deviation in ppm per each °C is shown on graph.
Also for easier grasp, here's summary data on chamber temperature span from +16 °C to +31 °C (temperature stability +/-0.005 °C). Perhaps bit easier on table below with calculated temperature coefficient and output deviation delta in ppm units. Voltage reading at +16.000 °C was taken as a baseline.

As we can see, temperature coefficient stays very close to +/-0.05 ppm/K specification. Also one has to remember than this test is essentially a comparison of internal HP 3458A LTZ1000-reference versus external. So accuracy of such measurements is already +/-0.1 ppm at best. To perform better measurement, one would need measurement equipment more stable than old aged HP 3458A, which leaves very few options, like very expensive JJA systems or characterized bank of Fluke 732A/732B/734A DC standards and low-noise null-meter.



RAW samples data in DSV-format is available as well, if you reader desire to conduct own analysis.

DSV-data log with temperature chamber test

I still have it running to raise temperature up to 50 °C, so will update data after test samples arrive :)
« Last Edit: October 20, 2016, 03:08:53 pm by TiN »
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Offline Cerebus

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #24 on: October 26, 2016, 12:04:09 pm »
Because the Zener in the LM399 is operated at such a low current [no matter how much current you pump into the device], you will see this "popcorn noise" more often with that part.

This is worth emphasising because a lot of people miss this. Internal to the LM399 is an, internally regulated, constant current supply that pushes 250 uA through the zener. Any excess current is shunted off by a pair of transistors that just turn the excess into heat. This doesn't mean that you can get away with feeding the LM399 with an unregulated current but you won't gain anything by going over the recommended 1 mA.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #25 on: October 28, 2016, 02:27:45 am »
Hi TiN,

do you still have some of this PCB unpopulated?

Thanks,

Domenico
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #26 on: October 28, 2016, 02:40:49 am »
Hi,

I have two left, but I need them for few items in near future. Somebody here is waiting for fab using my gerbers, I believe.
Btw, I done log with K2001 for you, but have no time recently to make pretty graph. Live graph and RAW data is here. Plenty of data there to run STDEV, noise pk-pk analyze and such. K2001 column is k10v.
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Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #27 on: October 28, 2016, 04:08:09 am »
Hi,

I have two left, but I need them for few items in near future. Somebody here is waiting for fab using my gerbers, I believe.
Btw, I done log with K2001 for you, but have no time recently to make pretty graph. Live graph and RAW data is here. Plenty of data there to run STDEV, noise pk-pk analyze and such. K2001 column is k10v.
I have 4 TiN boards, but all populated. All are currently measured with recently calibrated 3458A/002.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #28 on: October 28, 2016, 04:19:44 am »
plesa
How's your datalogging setup going on? If you wish, I can give you space on my serv and script, so your Pi can upload CSVs periodically and I can have live plot page for you :)
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Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #29 on: October 28, 2016, 05:24:27 am »
plesa
How's your datalogging setup going on? If you wish, I can give you space on my serv and script, so your Pi can upload CSVs periodically and I can have live plot page for you :)

Thanks I already have local website on RPi2 which use also the https://d3js.org/ for graphs.
It is quite amazing, BME280 will be connected soon for environment logging.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #30 on: October 28, 2016, 05:26:03 am »
I'd love to see some data too  :)
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #31 on: October 28, 2016, 07:25:07 pm »
Thanks TiN ... noise is identical.

Anyway just ordered 20 pcb of your project, if someone needs some I have few spares.
« Last Edit: October 28, 2016, 11:24:40 pm by mimmus78 »
 
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Offline pelule

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #32 on: October 29, 2016, 08:19:51 am »
@ mimmus78
Quote
Anyway just ordered 20 pcb of your project, if someone needs some I have few spares.
Just to be sure, I have the right "project" in mind. Does you have ordered this?
https://xdevs.com/doc/xDevs.com/KX_STR/top.jpg

If so, I would be interested into 2 to 4 boards.
You will learn something new every single day
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #33 on: October 29, 2016, 07:25:04 pm »
Well I ordered 20 PCB. I will keep 3 for me and the rest I can sell. I will actually build only one kit, I don't think I will use more than 3 pcb because this kit will cost more than 300 EUR.

I spent 160 EUR per the 20 pcb included express shipping and slow fabrication.  So it's 8 EUR + shipping for one.
Shipping for PCB will be done by registered mail. Usually it takes 10 days for US and one week for europe.
I will not do DHL/UPS shipping because this will require customs declaration and invoicing that I really don't like to do.

I asked for a quote to vishay for restors just for myself... but  maybe we can group buy also this resistors (here is 60%~ of kit costs).
Unfortunately shipping those 200 EUR worth of resistor cannot be done by standard mail ... so it may turn out not so convenient.

As in the other thread, if you like to have some pcb just add your name to the list.

Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
==================================
Remaining Boards: 8pcs
« Last Edit: October 29, 2016, 07:28:52 pm by mimmus78 »
 

Offline Nuno_pt

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #34 on: October 29, 2016, 07:31:58 pm »
There is no need for the Vishay VHP, you can use UXB, UPW20/50 or from Edwin, 0.1% 3ppm/C°
« Last Edit: October 29, 2016, 08:35:56 pm by Nuno_pt »
Nuno
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Offline klaus11

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #35 on: October 29, 2016, 08:32:49 pm »
Así que pedí 20 PCB. Voy a seguir 3 para mí y para el resto puedo vender. De hecho, me construiré un solo kit, no creo que voy a utilizar más de 3 PCB ya que este kit tendrá un costo de más de 300 euros.

Pasé 160 euros por el 20 de PCB, con el envío expreso y fabricación lento. Por lo que es de 8 euros + gastos de envío para uno.
Envío de PCB se hará por correo certificado. Por lo general, se tarda 10 días en los Estados Unidos y una semana para Europa.
No haré el envío de DHL / UPS, porque esto requerirá declaración de aduanas y la facturación que realmente no me gusta hacer.

Pedí una cita para Vishay para restors sólo para a mí mismo ... pero tal vez podemos agrupar comprar también esta resistencias (en este caso es del 60% de los costes ~ kit).
por desgracia envío de los 200 euros de resistencia no se puede hacer por correo ordinario ... por lo que puede resultar no tan conveniente.

al igual que en el otro hilo, si le gustaría tener un poco de PCB sólo tiene que añadir su nombre a la lista.

Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
klaus11: 2pcs
================= =================
restante Juntas: 6pcs
HP3458A, HP3245a, Keithley 2000, Fluke 87V, Rigol DP832, TEK TDS5052B, HP33120A
 

Offline VK5RC

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #36 on: October 29, 2016, 09:49:06 pm »
I would like 3 if available still
Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
klaus11: 2pc
VK5RC ;3pcs
Whoah! Watch where that landed we might need it later.
 

Offline t2kv

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #37 on: October 29, 2016, 09:57:05 pm »
And I'd like two if they're still available, please:

Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
klaus11: 2pc
VK5RC ;3pcs
t2kv: 2pc
 

Offline HighVoltage

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #38 on: October 29, 2016, 10:39:51 pm »
If there are any left, I take 2 pieces, thanks


Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
klaus11: 2pc
VK5RC ;3pcs
t2kv: 2pc
HighVoltage: 2pcs

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #39 on: October 30, 2016, 01:21:41 am »
High voltage we are one out ... if they send me some more board no problem.
 

Online David Hess

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #40 on: October 30, 2016, 01:13:01 pm »
It looks like a classic case of popcorn noise and not pink noise.  The level is awfully low and I cannot say that I have seen popcorn noise in a zener diode but the base-emitter transistor junction in series with the LTZ1000A zener could be responsible and combined with the low impedance at the collector would explain the low level.

Screening for popcorn noise is very difficult because of its often intermittent nature.  Long test times, hours to days, make it economically impractical for most customers.  I thought I remembered a note from LT about screening LTZ1000s for something but I looked and did not find it.
 

Offline Cerebus

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #41 on: October 30, 2016, 02:09:32 pm »
It looks like a classic case of popcorn noise and not pink noise.

Agreed that it looks like popcorn noise, but I think the explanation is wandering between zener and avalanche modes. Intrinsic to these low TC zeners is the balancing of the opposite tempcos of zener and avalanche effects. I think that's already been suggested hereabouts as a cause but I'm not sure. Popcorn noise is classically associated with relatively 'dirty' semiconductor processes which is why it's generally much less of a problem than it was, say, thirty years ago. We're dealing with a buried zener here, and the burying is done precisely to keep the junction away from the surface where impurities may lurk of the sort that cause popcorn noise.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online David Hess

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #42 on: October 30, 2016, 05:04:07 pm »
It looks like a classic case of popcorn noise and not pink noise.

Agreed that it looks like popcorn noise, but I think the explanation is wandering between zener and avalanche modes. Intrinsic to these low TC zeners is the balancing of the opposite tempcos of zener and avalanche effects. I think that's already been suggested hereabouts as a cause but I'm not sure. Popcorn noise is classically associated with relatively 'dirty' semiconductor processes which is why it's generally much less of a problem than it was, say, thirty years ago. We're dealing with a buried zener here, and the burying is done precisely to keep the junction away from the surface where impurities may lurk of the sort that cause popcorn noise.

The buried zener in this case is temperature compensated by the roughly -2mV/C Vbe of a series transistor so I am suggesting that the popcorn noise is actually coming from the transistor and not the buried zener reference.
 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #43 on: October 30, 2016, 07:16:26 pm »
The popcorn noise could come from the zener or the transistor - hard to tell from the data.

One could modify the circuit a little and compare the jumps. If the noise is sensitive to the zener current, this would indicate the zener as a source, if it changes with the transistor current it is likely coming from the transistor. The nice thing about the LTZ1000 circuit is than one change the currents relatively independent.

Even with that level of noise the reference might still be useful - maybe a a "two value" reference. The problem would only be if the popcorn noise gets slower and one gets only one level over a longer time - you than never know if it is the upper or lower level. So the preferred way would be to reduce the size of the jumps, not making the jumps less frequent - this could make thinks worse, even if you don't see the jumps anymore.

I don't see much sense in cooling and that way possibly destroying the chip. One might even think about using it for RMS conversion instead.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #44 on: October 30, 2016, 07:23:11 pm »
Quote
maybe a a "two value" reference
That's assuming both levels not change over time.

Quote
I don't see much sense in cooling and that way possibly destroying the chip
I don't see either, but desired to close this topic once and for all. Maybe we could see something in doing this (not necessarily at 77K temperature). Having 24/7 cooled to -30°C unit with TEC or phase-change loop (modified window AC) isn't that difficult, if there is point in it. I've ordered copper block at CNC shop to enclose module in hermetic box to place in dewar. This way there will be less rapid shock from contact with cooling liquid.
« Last Edit: October 30, 2016, 07:25:05 pm by TiN »
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Offline Cerebus

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #45 on: October 30, 2016, 11:52:23 pm »
The buried zener in this case is temperature compensated by the roughly -2mV/C Vbe of a series transistor so I am suggesting that the popcorn noise is actually coming from the transistor and not the buried zener reference.

Yes, the LTZ is using VBE compensation (and a lot of heat) rather than relying on zener versus avalanche tempco, but the zener versus avalanche thing is still going on because that's determined by the diodes 'set point*' voltage. I'm just influenced by the fact that there's some identifiable physics that we know goes on around this point. Anyway, the only way to be sure is to try the zener current versus transistor current experiment that's been suggested.

*Awkward terminology here because you'd normally say "zener voltage" or "avalanche voltage" but both are in play.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online David Hess

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #46 on: October 31, 2016, 10:30:21 am »
The buried zener in this case is temperature compensated by the roughly -2mV/C Vbe of a series transistor so I am suggesting that the popcorn noise is actually coming from the transistor and not the buried zener reference.

Yes, the LTZ is using VBE compensation (and a lot of heat) rather than relying on zener versus avalanche tempco, but the zener versus avalanche thing is still going on because that's determined by the diodes 'set point*' voltage. I'm just influenced by the fact that there's some identifiable physics that we know goes on around this point. Anyway, the only way to be sure is to try the zener current versus transistor current experiment that's been suggested.

*Awkward terminology here because you'd normally say "zener voltage" or "avalanche voltage" but both are in play.

As you pointed out, the zener is buried to prevent exactly this sort of problem.  I did a search but found nothing about popcorn noise in zener diodes which may just mean that it is such a minor problem that it takes an LTZ1000 before it becomes apparent since zeners are so noisy anyway.  I thought I remembered a comment from LT about special screening options for the LTZ1000 which included low frequency noise but was not able to find it.  In transistors, it is usually more apparent because of transistor gain but in this case, the low impedance collector load limits gain.

Since access is provided to the node between the buried zener and transistor base and actually every terminal of the transistor, testing to find the source is straightforward if not easy.

Tracking down popcorn noise was my motivation for expanding my collection of Tektronix oscilloscopes to include the 7A13 (1mV/div), 7A22 (10uV/div), and AM502 (10uV/div) differential vertical amplifiers.  It took me weeks to track down the example shown below because of its low level and especially intermittent nature where it was clean for hours at a time.
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #47 on: October 31, 2016, 06:45:07 pm »

I did a search but found nothing about popcorn noise in zener diodes which may just mean that it is such a minor problem that it takes an LTZ1000 before it becomes apparent since zeners are so noisy anyway.


Hello,

according to Warren they formerly selected 1N82x Zeners according to low frequency (= popcorn?) noise.

https://www.febo.com/pipermail/volt-nuts/2013-January/002362.html

see also attachement with a chart recorder.

http://www.febo.com/pipermail/volt-nuts/attachments/20130126/1fdc1ce7/attachment-0001.jpg

On another source I have read that ageing of zeners is correlated with low freqency (popcorn?) noise.
(which makes sense if you equal "popcorn noise" with "impure silicon").

With best regards

Andreas

 

Online fanOfeeDIY

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #48 on: October 31, 2016, 07:49:20 pm »
Hi mimmus78,

Thank you, if there is still left.

Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
klaus11: 2pc
VK5RC ;3pcs
t2kv: 2pc
HighVoltage: 2pcs
fanOfeeDIY: 2pcs
 

Online David Hess

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #49 on: October 31, 2016, 08:35:59 pm »

I did a search but found nothing about popcorn noise in zener diodes which may just mean that it is such a minor problem that it takes an LTZ1000 before it becomes apparent since zeners are so noisy anyway.

according to Warren they formerly selected 1N82x Zeners according to low frequency (= popcorn?) noise.

https://www.febo.com/pipermail/volt-nuts/2013-January/002362.html

see also attachement with a chart recorder.

http://www.febo.com/pipermail/volt-nuts/attachments/20130126/1fdc1ce7/attachment-0001.jpg

On another source I have read that ageing of zeners is correlated with low freqency (popcorn?) noise.
(which makes sense if you equal "popcorn noise" with "impure silicon").

Unfortunately I do not think the post really tells us anything.  Temperature compensated zener diodes like the 1N821 to 1N829 series include a forward biased PN junction in series just like the LTZ1000A and for the same reason so the popcorn noise still could be coming from either.

Popcorn noise is low frequency but the post confuses it with 1/f noise as well and the graph in the post shows 0.033ppm versus the 0.5ppm that TiN recorded.  Does that indicate two different sources or could it just be that the transistor in the LTZ1000A is amplifying it?  I wonder what the difference in time scale means if anything.

Isn't the connection between zener aging and popcorn noise simply because it takes time to detect?
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #50 on: November 08, 2016, 01:06:52 am »
Hi everybody,

pcb were fabricated and are now travelling to my home.
I should receive it tomorrow or Wednesday.
I will post PCB photo here when they arrive.

Ciao,

Domenico

-------------------------------------------------------------------------------------------------------------

Mimmus78: 3pcs
Nuno_pt: 3pcs
msliva: 3pcs
pelule: 3pcs
klaus11: 2pc
VK5RC ;3pcs
t2kv: 2pc
HighVoltage: 2pcs
fanOfeeDIY: 2pcs
 
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Offline Echo88

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #51 on: November 08, 2016, 01:22:46 am »
Damnit, havent seen that you sell these LTZ-PCBs here. Is there still one left for me to buy?
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #52 on: November 08, 2016, 07:57:39 pm »
Echo88, I don't think soo ... I already have some overbooking.

PCBs will arrive today.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #53 on: November 09, 2016, 12:53:08 am »
PCB arrived. They screw up couple of ring guard.

What we do? Do I have to ask for a refabrication or we keep as is?

One point they forget to remove soldermask. Other two points they leaved ring guard open by cutting the track.

Here attached sono photo.






Inviato dal mio Nexus 6P utilizzando Tapatalk

 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #54 on: November 09, 2016, 08:54:55 am »
Hi guys here are problems with those PCB I received today.
If for you is OK I will ask to fab to redo the lot.
Let me know what you think.
 

Offline Nuno_pt

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #55 on: November 09, 2016, 08:58:57 am »
Let's see what more experience people say about that, if we reach a conclusion that it's ok, then no problem for me.

But in all case I think you should tell the factory about this problem, just in case.
Nuno
CT2IRY
 

Offline ManateeMafia

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #56 on: November 09, 2016, 09:07:20 am »
Especially if they send a second batch of good boards out. Then you can pick and choose...

How do the boards look with a gerber viewing tool?
 

Offline VK5RC

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #57 on: November 09, 2016, 09:32:26 am »
I would be happy to pay for 3 of those boards,  others may want a re-spin.
My level of volt-nuttery (if you know what I mean) isn't too high. 
Whoah! Watch where that landed we might need it later.
 

Offline HighVoltage

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #58 on: November 09, 2016, 10:04:35 am »
I do not have enough experience with LTZ1000 PCB's to judge if this is a real problem or not.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #59 on: November 09, 2016, 10:10:16 am »
They have integrated GERBER PRE-VIEW, and was all OK.
You can carefully remove the solder mask by scraping and than eventually add some solder on one point, but these "broken" ring guard around LTZ1000 I don't know.
I think we are going to populate this board with 200/300 USD worth of components, and make a huge investment in time and money to characterise it.
I don't like the idea of having some unknown because someone decided to change PCB design.
I just wrote to the fab (I spotted also other solder mask not removed), let see what they say.
 

Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #60 on: November 09, 2016, 10:30:11 am »
I  suppose that open guard is not big difference if any. The majority of trace is still guarded.
Similar to solder mask covering guard trace. If someone is curios about difference you can measure it by electrometer.
Of course you can ask for some discount on PCB.
 

Offline klaus11

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #61 on: November 09, 2016, 08:14:13 pm »
Because of my absolute lack of knowledge, development and manufacture of PCBs, I have no idea what he is talking about. :-//
What the majority decides will also be good for me.
HP3458A, HP3245a, Keithley 2000, Fluke 87V, Rigol DP832, TEK TDS5052B, HP33120A
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #62 on: November 09, 2016, 09:20:51 pm »
So I submitted the original project from xdevs.com and those pcb where fabricated at Easyeda

I checked the gerber files with their online tool before submitting project and it was shown like the attached image.
At fist sight seemed OK to me including ring guard, but it's clearly not now, I should have checked better!
The problem is that on this part of the pcb the "solder mask" mask layer is not aligned with the trace.
They removed the solder mask, but there is no trace down. Il will check with TiN this point as the problem is likely in the files I downloaded from xdevs.com.

Anyway, as told you can still scrub this piece to get exposed guard.
As for the other problem I'm convinced too what plesa said: "I suppose that open guard is not big difference if any. The majority of trace is still guarded.".

So at this point, who still wants the PCB please send me by PM the address and if they prefer "registered mail" or "standard mail".
I will get quote for shipping and back to you with costs.


 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #63 on: November 09, 2016, 09:34:33 pm »
Updates on prices:

I spent 176 EUR total instead of preventivated 160. DHL charged me other 12 EUR for the customs declaration paperwork.
Anyway because I got 22 boards instead of 20, price will remain the same 8 EUR.
« Last Edit: November 09, 2016, 09:45:36 pm by mimmus78 »
 

Offline klaus11

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #64 on: November 09, 2016, 10:02:55 pm »
Mimmus, I'll stay with my two boards, if you have a post on how to correct the problem, why I still do not understand where the problem is due to my ignorance of English language comprehension
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #65 on: November 09, 2016, 10:41:23 pm »
Packaging:

 - VK5RC              3pcs       -       Paid - Registered
 - HighVoltage       2pcs       -      Paid - Registered - overbooking list
 - Mimmus78         3pcs       -       that's me

Confirmed waiting for payment:

 - klaus11              2pcs       -       Spain zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - t2kv                    2pcs       -       Australia zone 3 - priority mail 5.50 EUR  - registered 9.95 EUR
 - Nuno_pt             3pcs       -       Portugal zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - msliva               3pcs       -       Czech Republic  - zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR

Confirmed but in overbooking list (do not pay - wait):

 - SvanGool          2pcs        -       Netherlands  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list
 - fanOfeeDIY      2pcs       -       Japan - priority mail 5.50 EUR  - registered 9.95 EUR - overbooking list

=======================
TOTAL                  22 pcs
REMAINING         0 pcs


Waiting or confirmation

 - pelule               3pcs       -        please confirm and send me address for shipment quotation
=======================
TOTAL                3pcs


TOTAL CONFIRMED + UNCONFIRMED = 25
« Last Edit: November 11, 2016, 01:53:36 am by mimmus78 »
 
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Offline HighVoltage

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #66 on: November 09, 2016, 11:05:46 pm »
I am also stay to word and take 2 boards
PM sent
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #67 on: November 10, 2016, 08:33:00 pm »
I updated previous post with shipment costs.

A PM message with my PayPal address will be sent to everybody that sent me the complete address and get the shipment quotation.

Who is in overbooking please wait a couple of days, I'm still waiting a response from 4 members.
 

Offline HighVoltage

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #68 on: November 10, 2016, 09:48:09 pm »
Paypal sent
There are 3 kinds of people in this world, those who can count and those who can not.
 

Online fanOfeeDIY

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #69 on: November 10, 2016, 10:09:24 pm »
I updated previous post with shipment costs.

A PM message with my PayPal address will be sent to everybody that sent me the complete address and get the shipment quotation.

Who is in overbooking please wait a couple of days, I'm still waiting a response from 4 members.

Thank you for making the pcbs.
I may be in the overbooking list, I just replied to your PM.
 

Offline klaus11

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #70 on: November 11, 2016, 02:46:34 am »
I have not received PM message  :-//
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #71 on: November 11, 2016, 07:18:11 am »
I have not received PM message  :-//

PM sent
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #72 on: November 11, 2016, 07:26:38 am »
Packaging:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - HighVoltage       2pcs       -      PM SENT - Paid - Registered - overbooking list
 - Mimmus78         3pcs       -      that's me

Confirmed waiting for payment:

 - klaus11              2pcs       -       PM SENT - Spain zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - t2kv                    2pcs       -       PM SENT - Australia zone 3 - priority mail 5.50 EUR  - registered 9.95 EUR
 - Nuno_pt             3pcs       -       PM SENT - Portugal zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - msliva               3pcs       -       PM SENT - Czech Republic  - zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR

Confirmed but in overbooking list (do not pay - wait):

 - SvanGool          2pcs        -       Netherlands  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list
 - fanOfeeDIY      2pcs       -       Japan - priority mail 5.50 EUR  - registered 9.95 EUR - overbooking list


=======================
TOTAL                  22 pcs
REMAINING         0 pcs


Waiting or confirmation

 - pelule               3pcs       -        please confirm and send me address for shipment quotation
=======================
TOTAL                3pcs


TOTAL CONFIRMED + UNCONFIRMED = 25
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #73 on: November 11, 2016, 03:49:04 pm »
Sorry folks, I couldn't post before due to this cookery, but now I'm with you all  :-DD

First hats off to mimmus78, this was unexpected joy to see someone actually going to order my volt-nut design :D
The issues with soldermask opening is from my gerber file, I forgot to update the file B01. My own boards were corrected B02-version.
However those will not affect anything in measurable way, so it's still alright to use. If it bothers you, soldermask can be carefully scrapped off, but I'd leave it as is.

Other thing is manufacturing tolerance specs. I obviously did not expect someone to order the PCBs on usual hobby-level run fabs, so Gerbers are at 4mil/4mil spec. It does not have to be that precise, so I'll update it to be more friendly and replace GERBER on the article.

As of resistors, I would try to have best stability/tempco resistors for 1K/13K and 120 ohm ones, as these are key for LTZ1000 operation temperature and current. 70K can be less fancy and cheaper, and even vary in value 65-80K. You can see on HP 3458A A9 ref board there are just usual metal-films, and that board is totally fine to get <0.05ppm/K tempco, I tested it.

Opamps I use on my modules are controversial LTC2057 and now ADA4522-1 on this latest module covered in this thread before. No issues discovered.
Module can work with any input voltage from 10V to ~20V without problems and should not show dependence from input voltage. Regular LDO like 7815 with few decoupling caps will do job fine. Avoid switching PSUs though. There is no polarity protection on board, so double check connections and wiring before turning power on!
Normal current consumption with 1K/13K heater setting is ~28-32mADC steady state. It warms up to operation spec within 5-10 minutes.

Be careful with output too, it's not protected and directly connects to zener in LTZ1000A. If you short it or inject current into zener you are likely to cause stress/permanent damage the chip.
« Last Edit: November 11, 2016, 06:49:45 pm by TiN »
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Offline klaus11

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #74 on: November 11, 2016, 06:09:02 pm »
Paypal sent
HP3458A, HP3245a, Keithley 2000, Fluke 87V, Rigol DP832, TEK TDS5052B, HP33120A
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #75 on: November 11, 2016, 09:48:15 pm »
Packaging:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - t2kv                    2pcs       -      PM SENT - Paid - Registered
 - klaus11              2pcs       -      PM SENT - Paid - Priority
 - HighVoltage       2pcs       -      PM SENT - Paid - Registered - overbooking list
 - Mimmus78         3pcs       -      that's me

Confirmed waiting for payment:

 - Nuno_pt             3pcs       -      PM SENT - Portugal zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - msliva               3pcs       -        PM SENT - Czech Republic  - zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR

Confirmed but in overbooking list (do not pay - wait):

 - SvanGool          2pcs        -     Netherlands  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list
 - fanOfeeDIY      2pcs       -       Japan - priority mail 5.50 EUR  - registered 9.95 EUR - overbooking list


=======================
TOTAL                  22 pcs
REMAINING         0 pcs


Waiting or confirmation

 - pelule               3pcs       -        please confirm and send me address for shipment quotation
=======================
TOTAL                3pcs


TOTAL CONFIRMED + UNCONFIRMED = 25
 

Offline pelule

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #76 on: November 12, 2016, 03:13:04 am »
PM sent, still in for the 3 pcs.
You will learn something new every single day
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #77 on: November 12, 2016, 10:43:01 am »
Hi guys I have good news.

The PCB are going to be fabricated again ... they decided to be very nice, redo and ship the lot as soon as possible.
As consequence of this I think we have enough PCB for everybody :popcorn:

I think they are going just to correct the open guard track as they didn't asked me to send new gerbers.
I still don't have idea when we will get the new PCBs and if I will need to pay customs and VAT again.

What do we want to do?
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #78 on: November 12, 2016, 10:49:43 am »
Packaging:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - t2kv                    2pcs       -      PM SENT - Paid - Registered
 - klaus11              2pcs       -      PM SENT - Paid - Priority
 - HighVoltage       2pcs       -      PM SENT - Paid  - Registered - overbooking list
- pelule               3pcs       -        PM SENT - Germany zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - Mimmus78         3pcs       -      that's me

Confirmed waiting for payment:

 
 - Nuno_pt             3pcs       -      PM SENT - Portugal zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - msliva               3pcs       -        PM SENT - Czech Republic  - zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR

Confirmed but in overbooking list (do not pay - wait I receive second lot):

 - SvanGool          2pcs        -     Netherlands  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list
 - fanOfeeDIY      2pcs       -       Japan - priority mail 5.50 EUR  - registered 9.95 EUR - overbooking list
 - little                   2pcs.    -        Germany overbooking list

=============================
TOTAL                                  22 pcs
wait list (overbooking)          3  pcs
« Last Edit: November 13, 2016, 05:59:59 am by mimmus78 »
 

Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #79 on: November 12, 2016, 11:10:45 am »
What do we want to do?

Did you already ordered resistors? They have extra long leadtime or you are going to use some thin film like PTF56/UXB series?
Good choice can be Rhopoint ( they will fit to TiN boards )
https://www.rhopointcomponents.com/components/resistors/precision-through-hole/wirewound-miniohm-3ppmc-5e10-5g10-series.html
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #80 on: November 12, 2016, 11:33:30 am »
I contacted Edwin and Vishay. Finished to order some resistor from Edwin. I really don't even checked if this resistors will fit, but I'm also going to build my PCB version so for sure I will use it.

Still waiting for Vishay response, I really liked the idea to have this first board I build with Vishay. I asked fancy pants VHP101 for the heater divider a some other normal in plastic for the others 3.

The main problem I have is that I still don't have 3458A ... I'd like to try to buy same old rusty broken one if it will pop out somewhere, but you must be brave to do this extreme repairs like TiN.

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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #81 on: November 12, 2016, 06:26:16 pm »
Quote
but you must be brave to do this extreme repairs
No bravery needed, just have 2-3K$ cash handy and you will do fine. If A3 ADC bad - 1400$ for replacement. Repeat until it's stable :). It's no different than any other electronics repair, other than requirement of stable and verified calibration sources for DCV and OHM. For the first one you already on the correct way with LTZ module (you can calibrate 3458A to other calibrated 3458A using 7V LTZ output ;). I even had luck to transfer DCV internationally using A9 LTZ module, and got only 6ppm of error in the end.

I'm looking forward to see all you guys build some units and get them tested. I did not expect this thread to go this way,  :clap:.

As special case I'd be happy to offer calibration for your finished builds after it's all working and burned-in first 200 hours. Rules would be simple:

1. Build your KX-module, publish short worklog in this thread (few photos of assembled PCBA, photo of it running with DMM hooked up showing 7V)
2. Leave it running for 200 hours, so initial drifts get stabilized. Module should be enclosed in some box without vents.
3. Measure it again, record the temperature and voltage and put a label with values on the box
4. Ship the box to me (Taiwan). You pay shipping.
5. I'll power your box with +15V for 48 hours to have everything stabilize
6. Test 7V output voltage in temperature span +20....+30C, record the graph
7. Unit will be shipped back via EMS Express (~30-40$USD, 4-7 days to USA, bit more to EU). You pay shipping.

I don't have official Keysight/Tektronix/etc calibration certificates for my 3458A, but I'm confident it's +/-2ppm (likely <1ppm) on DCV.
All steps are required :)
« Last Edit: November 12, 2016, 06:27:49 pm by TiN »
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Offline VK5RC

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #82 on: November 12, 2016, 07:48:08 pm »
I would like to thank both TiN,  for putting his hard work designs up for open review/reproduction and Mimmus78 for putting in the pcb gerbers etc and doing all the postage / customs etc.
TiN,  if that offer re calibration check is open in a month or so,  it will be hard to refuse!
Robert
Whoah! Watch where that landed we might need it later.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #83 on: November 12, 2016, 07:50:30 pm »
Let's make it so: offer valid for any KX reference board once, without time limitation, unless my homelab get major change, which isn't planned.
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #84 on: November 12, 2016, 08:51:04 pm »
TiN this offer of free calibration will be interesting but we should find a way to ship back and forth without paying customs.

I should check how this can be done.

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Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #85 on: November 12, 2016, 09:53:57 pm »
I can offer you similar service like TiN in Europe.
1. Measure it with calibrated 3458A/002 in reasonable temperature range.
2 . For extreme voltnut  - close to me is JJA and they can measure it for 400 EUR / 2-3 weeks of monitoring.

What I will add is power cycling for few days ( On for 1h and off or 30min to cool down).
And maybe bake the LTZ1000 prior assembly.

For shipment can be handy to monitor temperture if you are going to ship it in winter time.
« Last Edit: November 12, 2016, 10:00:35 pm by plesa »
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #86 on: November 13, 2016, 12:17:05 am »
Plesa that's very nice for all European guys to have this opportunity.

O men you have JJA near home! I cannot even comment it.

Anyway regards Edwin resistors, despite last problems with quality in last year I think it is the best and cost effective way to get reasonably TC matched resistors for the heater.

Keep this ratio constant is 10 times more important that all other factors.

I read somewhere that resistors made by same person, one after the other can have similar drift and TC.
You can ask Vishay for this, but I this it will increase even more the costs. So I just asked Erwin for this and this seems to be the most practical and cheap way to get this point.
Hope he really solved issues with his epoxy in meantime.
« Last Edit: November 13, 2016, 12:34:50 am by mimmus78 »
 

Offline Alex Nikitin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #87 on: November 13, 2016, 12:32:20 am »
I can offer you similar service like TiN in Europe.
1. Measure it with calibrated 3458A/002 in reasonable temperature range.

I can do a similar service in the UK, if somebody needs it, as the HP3458A Opt 002 just came back from calibration at Keysight. I don't have a temperature chamber yet (though it may change soon), however I can monitor the lab temperature (or the reference enclosure temperature).

Cheers

Alex
 
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #88 on: November 13, 2016, 12:39:00 am »
plesa, Alex Nikitin
If you OK, I can add this section into article on my site, with links to your profile, to keep this program afloat? :)
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Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #89 on: November 13, 2016, 12:54:12 am »
plesa, Alex Nikitin
If you OK, I can add this section into article on my site, with links to your profile, to keep this program afloat? :)

Of course.
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #90 on: November 13, 2016, 01:04:59 am »
Fist shipment is ready ... I'm still waiting payment from other 4 members. Let me know if someone have any problem.

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« Last Edit: November 21, 2016, 07:16:59 pm by mimmus78 »
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #91 on: November 13, 2016, 01:07:22 am »
OK I think we just need one 3458a for Italy now. I should ask my wife ...

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Offline Alex Nikitin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #92 on: November 13, 2016, 01:36:41 am »
plesa, Alex Nikitin
If you OK, I can add this section into article on my site, with links to your profile, to keep this program afloat? :)

Yes, sure.

Cheers

Alex
 
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #93 on: November 13, 2016, 02:50:22 am »
Added a section about calibration offer on site  :-+

Also updated top post in thread. Thanks!

Calibration by Accuracy / Standard    Region/Country Contact for participants
  xDevs.com        <2ppm / 3458A-mod + 2*K2002 Asia/Taiwan      EEVBlog forum PM
  plesa            <4ppm / 3458A-002   Europe/Sweden    EEVBlog forum PM 
  Alex Nikitin      <4ppm / 3458A-002   Europe/UK        EEVBlog forum PM
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Offline HighVoltage

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #94 on: November 13, 2016, 03:46:36 am »
I am still in the middle of getting to know my 3458A (8 ppm) and will have it officially Keysight calibrated in a few month time. If anyone needs its KX reference board measured in Germany, you can send it to me, as long as you pay shipping. I can also offer a comparison to my 34470A and DMM7510.
But, until now I can not change the temperature, that is a future project.   
There are 3 kinds of people in this world, those who can count and those who can not.
 
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Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #95 on: November 13, 2016, 04:48:20 am »
Probably plenty of 3458As in the US, but I'm happy to offer comparisons with an in Cal DMM7510 and K2010.

I also have an 0.05% Hameg 8118 LCR.

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #96 on: November 13, 2016, 09:19:37 am »
This is going to be huge ... a global volt nut club.

Thanks to plesa I asked to rhopointcomponents.com too for a quote of the resistors. I will let you know what happens.
« Last Edit: November 13, 2016, 09:23:45 am by mimmus78 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #97 on: November 14, 2016, 07:56:10 pm »
UPDATES:
Hi guys, I shipped the 5 packages to VK5RC, t2kv, klaus11, HighVoltage, pelule.
For all that paid for registered main I will send them a PM with the tracking number.

I'm still waiting payment by: Nuno_pt, msliva. I sent them 2 PM but they seems kinda busy now.
I have other 8 spare PCBs, I think if I don't get notice from them I a couple of days I will start accept payment from to the "overbooking list".

Shipped:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - t2kv                    2pcs       -      PM SENT - Paid - Registered
 - klaus11              2pcs       -      PM SENT - Paid - Priority
 - HighVoltage       2pcs       -      PM SENT - Paid  - Registered - overbooking list
- pelule               3pcs       -        PM SENT - Germany zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - Mimmus78         3pcs       -      that's me

Confirmed waiting for payment:
 
 - Nuno_pt             3pcs       -      PM SENT - Portugal zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - msliva               3pcs       -        PM SENT - Czech Republic  - zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR

Confirmed but in overbooking list (do not pay - wait I receive second lot):

 - SvanGool          2pcs        -     Netherlands  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list
 - fanOfeeDIY      2pcs       -       Japan - priority mail 5.50 EUR  - registered 9.95 EUR - overbooking list
 - little                   2pcs.    -        Germany overbooking list

=============================
TOTAL                                  22 pcs
wait list (overbooking)          3  pcs
 
The following users thanked this post: VK5RC

Offline Dr. Frank

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #98 on: November 14, 2016, 08:15:28 pm »
I can offer you similar service like TiN in Europe.
1. Measure it with calibrated 3458A/002 in reasonable temperature range.

I can do a similar service in the UK, if somebody needs it, as the HP3458A Opt 002 just came back from calibration at Keysight. I don't have a temperature chamber yet (though it may change soon), however I can monitor the lab temperature (or the reference enclosure temperature).

Cheers

Alex

Plesa, Alex, and also HighVoltage:

What kind of KS calibration and report for your 3458As did /will you get?

The single page report, which only confirms that the instrument is in 1 years specification limits, or the elaborate, much more expensive, multi page calibration report, with all measurement results (as found) including test limits?

I think, if it's only the first kind, it won't be sufficient for this purpose, as the 1 year DCV specification is 8ppm / 4ppm for option 002 only, and about <= 1ppm uncertainty is required.

Frank
« Last Edit: November 14, 2016, 08:20:57 pm by Dr. Frank »
 

Offline Alex Nikitin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #99 on: November 14, 2016, 09:54:42 pm »

What kind of KS calibration and report for your 3458As did /will you get?

The single page report, which only confirms that the instrument is in 1 years specification limits, or the elaborate, much more expensive, multi page calibration report, with all measurement results (as found) including test limits?

Hi Frank,

Here is a page from the certificate. I hope it answers your question.

Cheers

Alex
 

Offline HighVoltage

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #100 on: November 14, 2016, 09:59:08 pm »
Dr.Frank,
My plan is to have my 3458A adjusted and calibrated to the higher specs and I want the multi page calibration report. But I have not even started to talk to KS. May be I will visit KS Boeblingen first to see their capabilities and then make my mind up. On the other side, I can also have it calibrated in Hamburg against a calibrated 732A. But first I will have the instrument running for a few more month to get it stable.
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Offline Dr. Frank

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #101 on: November 14, 2016, 10:35:32 pm »


Hi Frank,

Here is a page from the certificate. I hope it answers your question.

Cheers

Alex

Alex, definitely.. your 10VDC uncertainty will be around 3ppm, probably better, as the 10Vdc reading of your instrument is given to < 1ppm resolution, and the "Golden 3458A", which defined the limits, may have been less uncertain than 1ppm.

For sure, this calibration did cost a fortune.  :-+

Frank
 

Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #102 on: November 15, 2016, 04:26:53 am »
Alex, definitely.. your 10VDC uncertainty will be around 3ppm, probably better, as the 10Vdc reading of your instrument is given to < 1ppm resolution, and the "Golden 3458A", which defined the limits, may have been less uncertain than 1ppm.

I have same uncertainties like Alex, because we are sharing calibration lab :)
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #103 on: November 15, 2016, 06:52:02 am »
At the end I ordered 2 more sets of resistors (the one DR. Frank used) ... unfortunately there was no stock of 1K value up to the end of this month. So it's still waiting time ...

I'll build a couple of pieces with TiN PCB and use this as reference. After this I will build a couple with my "new" design.

In this new design, I'd like to experiment a little new gimmick with a "new" schematics that is my interpretation of years of post of the old LTZ1000 thread.

It will be not an extreme design, just take the best ideas of the old thread and put all together (some Andreas's noise reduction caps, Solartron's caps on the heater and the new op-amp TiN used in his last build, but I still have to decide final op-amp).

I'd like to add also a buffer for the 7V output to prevent problems with shorting the zener. Maybe also revive the 7.X to 7 and 7 to 10 ratio scaling used by Dr. Frank.

Hope I have time and skills to complete the design with some good result (I have not such experience with analogue stuff).

Inviato dal mio Nexus 6P utilizzando Tapatalk
« Last Edit: November 15, 2016, 08:07:52 am by mimmus78 »
 

Offline zucca

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #104 on: November 15, 2016, 09:17:16 pm »
mimmus78 please consider to do more boards when you are ready. I would like to buy one... may I?
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #105 on: November 15, 2016, 09:41:37 pm »
Zucca, where is the one assembled one you have already? :)
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #106 on: November 15, 2016, 10:06:15 pm »
mimmus78 please consider to do more boards when you are ready. I would like to buy one... may I?

Added you to overbooking list.

I still have 8 spare from some users here they didn't confirmed, I will wait up to the end of the day and than offer to the one that are on queue on the overbooking list ... anyway another lot is going to be fabricated.

D.

UPDATED:

Packaging and shipping on Friday:

 - Nuno_pt             3pcs       -      PM SENT - Portugal zone 1 - priority mail 3.50 EUR - registered 7.90 EUR

Shipped:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - t2kv                    2pcs       -      PM SENT - Paid - Registered
 - klaus11              2pcs       -      PM SENT - Paid - Priority
 - HighVoltage       2pcs       -      PM SENT - Paid  - Registered - overbooking list
- pelule               3pcs       -        PM SENT - Germany zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - Mimmus78         3pcs       -      that's me

Confirmed waiting for payment:
 
 - msliva               3pcs       -        PM SENT - Czech Republic  - zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR

Confirmed but in overbooking list (do not pay - wait I receive second lot):

 - SvanGool         2pcs        -     Netherlands  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list
 - fanOfeeDIY      2pcs       -       Japan - priority mail 5.50 EUR  - registered 9.95 EUR - overbooking list
 - kutte                2pcs.    -       Germany  zone 1 - priority mail 3.50 EUR  - registered 7.90 EUR - overbooking list

=============================
TOTAL                                  22 pcs
wait list (overbooking)          4  pcs
« Last Edit: November 17, 2016, 02:45:46 am by mimmus78 »
 

Offline zucca

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #107 on: November 16, 2016, 09:32:22 am »
Thx mimmus just one thing I am in Germany not in Italy...  ma sono italiano...

TiN... the one I have is just ready for testing my K2001. Later I plant to put it in the K2001 ADC replacing the VR801 6.4 V Zener...  :box: :-// :scared: just curious to see what will happen
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Offline zucca

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #108 on: November 16, 2016, 07:17:13 pm »
Ohh I got a PM from Mimmus confirming that the boards in discussion is the TiN one... but I meant the Mimmus new design one, which is not ready yet. Soo please take me out from the list and put me in he new one of your design.

Thanks TiN again for sending me his wonderful KX LTZ1000A board.
Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #109 on: November 16, 2016, 09:15:28 pm »
@zucca no problem ... I'll keep you posted if I manage to finish my design in next weeks.
@Nuno_pt I will ship your package on Friday.

As in not hearing from msliva in days I will send PM for payment instruction also to the overbooking list ...
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #110 on: November 17, 2016, 02:47:50 am »
I don't understand why use VR801 as integrator reference? Any reason why not route LM399 ref signal there?
 

Offline SvanGool

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #111 on: November 17, 2016, 02:50:24 am »
@mimmus78, as you requested to report on the forum:
I sent you the money for: - SvanGool         2pcs        -     Netherlands  zone 1 - priority mail 3.50 EUR - overbooking list

Thanks !
# Don't hurry, the past will wait. #
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #112 on: November 17, 2016, 03:07:46 am »
3 more PCB to go.
 

Offline kutte

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #113 on: November 17, 2016, 03:20:38 am »
20,00 Euro for 2 boards via priority mail sent from kutte
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #114 on: November 17, 2016, 07:01:45 am »
Thanks Guys, PCB are over.
I didn't hear from the fab for the "fixed" batch, I will let you know when then new batch will arrive.
Anyway let me know if someone else is interested.
 

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #115 on: November 17, 2016, 07:08:58 am »
Anyway let me know if someone else is interested.

If you end up ordering another batch, I'll take 5 to the USA.

Online fanOfeeDIY

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #116 on: November 17, 2016, 08:21:03 pm »
Hi mimmus78,

Thank you for your message. I am in the overbooking list.
I missed reading it last night, but it is fine. I will wait for the next batch.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #117 on: November 17, 2016, 09:06:23 pm »
UPDATED:

Packaging and shipping on Friday:

Shipped 18/11/2016:

 - Nuno_pt             3pcs      -     PM SENT - Paid - Priority
 - SvanGool           2pcs      -     PM SENT - Paid - Priority
 - kutte                   2pcs      -     PM SENT - Paid - Priority

Shipped 11/11/2016:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - t2kv                    2pcs       -      PM SENT - Paid - Registered
 - klaus11              2pcs       -      PM SENT - Paid - Priority
 - HighVoltage       2pcs       -      PM SENT - Paid  - Registered - overbooking list
- pelule               3pcs       -        PM SENT - Germany zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - Mimmus78         3pcs       -      that's me

Confirmed:
 
 - msliva               3pcs       -        PM SENT
 - fanOfeeDIY      2pcs       -       PM SENT
 -  dr.diesel           5pcs       -       PM SENT
 - z01z                  3pcs       -       PM SENT
« Last Edit: November 18, 2016, 10:45:52 pm by mimmus78 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #118 on: November 17, 2016, 09:18:38 pm »
So this is what I elaborated. This is based mainly on last revision of battery powered reference from "andreas".

I added reverse polarity power protection.
Removed some caps that Dr. Frank defined as "fear" caps.
I removed the MOS that drive current to the zener.
Using LTZ1000 (not A version)

I was thinking to add some basic output protection to the REF ... what you think to add something like this (with opportune op-amp):



 just after the buffered output of the LTZ1000A?



As usual care to thermal EMF is a must. Hope it will not upset much the output.
« Last Edit: November 18, 2016, 02:43:52 am by mimmus78 »
 

Offline zucca

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #119 on: November 17, 2016, 09:59:16 pm »
Mimmus can you put some 0R jumpers or somenthing to separate the heater power supply path from the rest? See TiN article here:

Quote
Solder coax wire to +18.5V and power GND to provide separate current path for LTZ’s heater, so it would not upset reference output
« Last Edit: November 17, 2016, 10:02:38 pm by zucca »
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Offline zucca

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #120 on: November 17, 2016, 10:14:44 pm »
I don't understand why use VR801 as integrator reference? Any reason why not route LM399 ref signal there?

+1 I really don´t know why...
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #121 on: November 17, 2016, 11:55:45 pm »
Mimmus can you put some 0R jumpers or somenthing to separate the heater power supply path from the rest? See TiN article here:

Quote
Solder coax wire to +18.5V and power GND to provide separate current path for LTZ’s heater, so it would not upset reference output

I added R10 just before the heater transistor, this can be 0R or used also to split VCC.
I don't know if is good to add also on the GND side.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #122 on: November 18, 2016, 12:17:01 am »
Hi guys, I got called from DHL because there is a new parcel for me (and I wasn't home) ... so guess what it will be?
I will let you know when back in home if it's some gift from unknown or if it's the new KX pcb batch.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #123 on: November 18, 2016, 06:40:11 am »
New pcb lot arrived. This new lot has no missing part on the guard ring around LTZ1000.

I will ship this new lot in parcels shipping tomorrow, and it seems we will have enough pieces also for how was in the overbooking list.

If someone that get the old PCB cannot sleep with the mistaken one I can ship the new corrected PCB for free (you just pay postage). This offer is valid just for few days.

I will send pm later to the ones that where in overbooking list.





Inviato dal mio Nexus 6P utilizzando Tapatalk

 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #124 on: November 18, 2016, 06:49:23 am »
So this is what I elaborated. This is based mainly on last revision of battery powered reference from "andreas".


Hello,

are you shure that C10 is on the "right" side of the resistors?

With best regards

Andreas


 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #125 on: November 18, 2016, 07:46:08 am »
Using chopper OPs for the LTZ1000 circuit can get tricky. They produce quite some RF spikes can have higher noise in kHz range, where the transistor in the LTZ is not helping anymore. There is no real need to replace the LT1013 or similar OP. The LT1013 is not that expensive. But at least dual OPs use the same pinout.

For the extra butter, the AZ OP is suitable, as here the error from the OP fully enters.
One might think about having some RC filtering here - to reduce higher frequency noise from the reference and keep spikes from the AZ OP away from the reference.

With a relatively high current, there was a good reason to have a transistor / JFET to drive the reference current. If one really wants to save on this, one could still use a bridge or diode like shown, but I would really have the space for the transistor on the board.

 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #126 on: November 18, 2016, 08:16:21 am »
Hello,

Using chopper OPs for the LTZ1000 circuit can get tricky. They produce quite some RF spikes can have higher noise in kHz range, where the transistor in the LTZ is not helping anymore. There is no real need to replace the LT1013 or similar OP. The LT1013 is not that expensive. But at least dual OPs use the same pinout.

Do you have founded measurement values on this?
I have not measured any differerence between LT1013 and LTC2057 on my latest 4 references.

For the extra butter, the AZ OP is suitable, as here the error from the OP fully enters.
One might think about having some RC filtering here - to reduce higher frequency noise from the reference and keep spikes from the AZ OP away from the reference.
+1
I fully agree I measured large differences between filtered and unfiltered buffer regarding EMI sensitivity.

With a relatively high current, there was a good reason to have a transistor / JFET to drive the reference current. If one really wants to save on this, one could still use a bridge or diode like shown, but I would really have the space for the transistor on the board.
The main intention of the FET-Buffer was LT1013-related together with reduced power supply voltage.
keep heating away from LT1013 with relative high offset drift
+ extend output voltage range of the LT1013 (level shift) for reduced battery voltage.

So with a rail to rail chopper I see no reason to use a (now obsolete) FET.
The initial design is now already 6 years old.

With best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #127 on: November 18, 2016, 11:30:43 am »
are you shure that C10 is on the "right" side of the resistors?

Well yes, better to move it before. The idea is to have a low pass filter to reduce the noise, and maybe also EMI. Don't know how and if it will works.

I added also some load on the buffered output ... what I have to check on datasheet to confirm 47K is sufficient (maybe Peak to Peak Current Noise)?

I added also limit to output swing of the protection circuit ... this will protect from almost any negative or something like > 11V + couple diode drop.
Do not expect any CAT rating here, it may be not sufficient to save the last opamp but at lest rest of reference should be safe if some low voltage is applied to the binding posts by error.
Anyone have a good example of 10V reference protection? Don't know how much this will upset the result.
 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #128 on: November 18, 2016, 07:50:32 pm »
The "filter" around R15,R16 C10 is there to make the buffer amplifier tolerant to capacitive load.

I don't really understand the protection circuit shown at the output -  to me this makes little sense. If needed at all I would more expect kind of a beefy 8 V zener diode or equivalent circuit.

One point where an extra protection might make some sense would be the unbuffered output. This is known to be sensitive to a short or overload (e.g. large uncharged capacitor), as this would cause the heater to activate all the way. A protection could check for a drop of the output by more than an few millivolts and in this case turn down the heater. It could take as little as a tl431 and a few resistors and a diode.
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #129 on: November 18, 2016, 09:48:11 pm »
Hello,

that´s what I have planned for my Rev "C" board.
C23 EMI filtering.
R25 C24 (wideband) noise filtering and limiting back current to LTZ1000 zener via the OP-Amp input protection diodes in case of output shortening.

(I am still looking for good ideas for a temperature stable 7 to 10V transfer)

with best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #130 on: November 18, 2016, 10:57:01 pm »
UPDATED 2016 Nov 25 - 22:30 Italy time

We still have: 8 PCBs with 1mm guard missing

Waiting for payment:
 
 - msliva               3pcs
-  bingo60            2pcs

=========================================================

Shipped 25/11/2016:

 - z01z                  3pcs (new pcb)
 - SvanGool          2pcs (new pcb)
 - fanOfeeDIY       2pcs (new pcb)
 - villas                  2pcs (new pcb)

=========================================================

Shipped 18/11/2016:

 - Nuno_pt             3pcs      -     PM SENT - Paid - Priority
 - SvanGool           2pcs      -     PM SENT - Paid - Priority
 - kutte                   2pcs      -     PM SENT - Paid - Priority
 - dr.diesel           5pcs       -       PM SENT - Paid - Registered

=========================================================

Shipped 11/11/2016:

 - VK5RC              3pcs       -      PM SENT - Paid - Registered
 - t2kv                    2pcs       -      PM SENT - Paid - Registered
 - klaus11              2pcs       -      PM SENT - Paid - Priority
 - HighVoltage       2pcs       -      PM SENT - Paid  - Registered - overbooking list
- pelule               3pcs       -        PM SENT - Germany zone 1 - priority mail 3.50 EUR - registered 7.90 EUR
 - Mimmus78         3pcs       -      that's me

=========================================================
« Last Edit: November 26, 2016, 08:50:44 am by mimmus78 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #131 on: November 18, 2016, 11:03:55 pm »
I don't really understand the protection circuit shown at the output -  to me this makes little sense. If needed at all I would more expect kind of a beefy 8 V zener diode or equivalent circuit.

Yes I rushed a little bit the design, and this is ok for just ~ 0.6V. Considering sense is attached to the binding posts maybe just some zeners is enough.

One point where an extra protection might make some sense would be the unbuffered output. This is known to be sensitive to a short or overload (e.g. large uncharged capacitor), as this would cause the heater to activate all the way. A protection could check for a drop of the output by more than an few millivolts and in this case turn down the heater. It could take as little as a tl431 and a few resistors and a diode.

I don't plan to expose this network outside the reference ... maybe this ca be still useful if some op-amp will die. I will check it.

How to calculate what minimum load I need to present to the op-amp?


 

Offline villas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #132 on: November 19, 2016, 04:14:42 am »
I would like to build one reference, but I probably will not be able to find the resistors here and I don't like the idea getting these from eBay.
Do you guys plan to group buy the low TC resistors from VPG or some distributor?
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #133 on: November 19, 2016, 06:43:41 am »
Flintstone: this R is used for temperature compensation in LTZ1000A and is not necessary in not A version.

Inviato dal mio Nexus 6P utilizzando Tapatalk

 

Offline d-smes

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #134 on: November 19, 2016, 07:12:09 am »
this R is used for temperature compensation in LTZ1000A and is not necessary in not A version.
It's the other way around per data sheet-  don't use resistor for "A" version.
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #135 on: November 19, 2016, 07:22:18 am »
Ohh guys I was 100% sure was the other way around ...  |O
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #136 on: November 19, 2016, 08:13:59 am »
Hello,

I use R9 also for the A version to fine adjust the T.C.
But not always 400K is the right value:

https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/?action=dlattach;attach=253898

with best regards

Andreas
 

Offline bingo600

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #137 on: November 19, 2016, 09:03:48 am »
@mimmus78

I'd like to get 2 boards from the "overbooking list" if possible

/Bingo
 

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #138 on: November 19, 2016, 09:52:30 am »
Did you already ordered resistors? They have extra long leadtime or you are going to use some thin film like PTF56/UXB series?
Good choice can be Rhopoint ( they will fit to TiN boards )
https://www.rhopointcomponents.com/components/resistors/precision-through-hole/wirewound-miniohm-3ppmc-5e10-5g10-series.html

Wow, they stock a big range of 3PPM parts!  I don't have any experience with these guys unfortunately, might be a good alternative depending on how busy Edwin's shop is.

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #139 on: November 19, 2016, 11:38:29 am »
Here are options I found:

Vishay VHP101
VHP101 is the most stable and expansive resistors you can get (few PPM for years or °C) ...
if you have big pocket and a very special LTZ1000 you can use this two for the heater divider.
Using VHP101 also for the other resistors to me is just a waste of money.
If you like Vishay name S102C and Z202 are good too, and they can be used for
the other resistors at half the price of the VHP101.

TE Connectivity UPW50

UPW50 has TC 3PPMx°C and 25PPM x year stability.
You can buy at rs components or other store at 7 to 10 EUR each one.
Not all values are directly available, so you must buy multiple items to form the 70K and the 12K resistors.
I brought two sets and I spent less than 150 EUR for both @ rs components. You can find this on findchips.

ECONISTOR 8G16D @ rhopointcomponents
Very similar specs and price to UPW50 but you can request for custom values of "70K" and "12K" values.
They have higher EMF from UPW50. I get a quotation as low as 50 EUR per set. Cannot find this on findchips.

EDWIN
It's the cheapest of all others, specs are similar to the others (UPW50, ECONISTOR) but you have few weeks of lead time.
He had some problems in past with this resistors. I ordered 3 sets from him too, let's see when they arrive.
« Last Edit: November 19, 2016, 11:44:53 am by mimmus78 »
 
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Offline SvanGool

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #140 on: November 19, 2016, 11:06:38 pm »
I would like to build one reference, but I probably will not be able to find the resistors here and I don't like the idea getting these from eBay.
Do you guys plan to group buy the low TC resistors from VPG or some distributor?

For the last days, I was in contact with Edwin (the resistor expert) about the resistors for this project, although most answers can be found in the several LTZ1000 threads, I found them very useful, a little summary (with permission of Edwin):
  • Q : People advise me to use 12k5 or 13k iso 12k for the heater in case of a LTZ1000A (which I have), can you advise?
  • A1: In the case of the LTZ circuits, using resistors such as the Vishay Z202 and VHP203 will not get you any noticeable improvement in the Vref's performance.  That circuit is quite insensitive to low resistor TCR and low long term drifting.  Where the resistor performance becomes much more important is in the circuit that raises the LTZ voltage to about 10V at the output.  The best performance of the LTZ is achieved with the Linear Tech circuit as given in the data and app notes.
  • A2: The LTZ1000 (non-A) does allow for a slightly lower overhead temperature internally, about 5°C above the highest environmental temperature expected in operation, whatever the source may be, internal instrument temperature may be higher than room temperature.  Use of 12K, 12.5K, or 13K with the 1000 is often acceptable.  What you don’t want is for the LTZ to run out of compensation room for temperature because it will no longer be able to compensate for temperature and you will see a significant change in output voltage.
  • A3: For the LTZ1000A version, it requires at least 10°C overhead in temperature, this usually required at least 13K or higher.  According to LT, beginning about two years ago, the new production of the ‘A” version was recommended to use a 15K resistor period, this is the value (HP, Agilent,) Keysight, and Fluke are using in their units (the 3458A, ECT.). If I was building an LTZ module I would use the 15K as recommended.
  • Q : Do these heater divider resistors need to be thermally coupled (tracking TC), how would I do that?
  • A : The heater divider resistors is a bit sticky, if you encapsulate the module in say foam and not just a ‘box’, the resistors will achieve equilibrium without any special effort.  If the module is not encapsulated, then wrapping a layer of copper tape around the two resistors will make a significant difference in tracking.  You must remember that whatever the case is, it is going to take some time for everything to warm up and equalize, until then you will see a higher than ‘normal’ drift.  If after about 30-60 minutes you are still seeing some wobble, you have an air draft problem most likely.
  • Q: What is the best way to mount these type 802 resistors in TiNs 0,125" and 0,150" PCB sockets and can I use normal SnPb solder?
  • A : The dimensions of the 802 is 0.250” D x 0.375” L (6.35mm x 9.53mm) with 22 AWG leads, leaded solder is just fine.
  • Q : Do I have to take some special precautions to protect your  resistors against humidity?
  • A : No, the resistors are not humidity sensitive to any significant degree.
  • Q : What would be the cost and lead time for your resistors and could a group discount be applicable?
  • A: For 1-9 pieces, a group buy would lower these prices and reduce shipping cost (1st Class International is $13.50, International Priority is $33.95 for Europe):
    1x  120R0, ±0.1%, type 802       $6.85
    1x  1K, ±0.1%, type 802          $6.34
    1x  12K or 15K, ±0.1%, type 802  $7.35
    2x  70K, ±0.1%, type 802         $8.64

    Current ship dates are approximately 4-5 weeks, perhaps a little less depending on circumstances.

 :-+
« Last Edit: November 19, 2016, 11:30:10 pm by SvanGool »
# Don't hurry, the past will wait. #
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #141 on: November 21, 2016, 06:20:15 am »
UPDATE 25/nov/2016 22:30 Italy time:

All PCB in new batch are already sold but if you accept the one with this small defect I still have someone unsold that I'm not going to use.
If you want it just send me a PM.

Updated pcb shipping status --> HERE
« Last Edit: November 26, 2016, 08:51:28 am by mimmus78 »
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #142 on: November 26, 2016, 08:54:00 am »
RS components today shipped me the last two precision resistor I was missing for starting build this KX reference.
Is there any easy and effective way to check TC of the resistors without having a thermal chamber?
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #143 on: November 26, 2016, 09:30:38 am »
Hello,

I do it with a peltier (car) cooling box + heater foils on a heat spreader for a ~30 deg C temperature range:
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg462298/#msg462298

Frank uses a freezer cooling pad in a isolated box.
https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg466319/#msg466319

If you want repeatable measurements you should keep the wires of the resistor at the same temperature.
I use aluminium stripes + silicone pads

With best regards

Andreas
 
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Offline Dr. Frank

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #144 on: November 26, 2016, 10:02:08 am »
Well, I'm using a dynamic temperature change method, so the measurement are always done during ramping up/down of the temperature.
If that change is slow enough, nearly everything is in equilibrium, and the measurement will be precise enough.

My final setup is here: https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg617211/#msg617211

The aluminium block, which carries the resistor and the thermometer are additionally mounted inside an outer aluminium box so that also all the wires are on the the same temperature as the alu block and the outer case (thermal short circuit), This is essential, as most of heat transfer happens via the resistors wires.

I only have difficulties to observe very slow events correctly, like the described hysteresis and creeping effects on some of the econistor resistors.

It would  be very useful to let the resistors relax on a constant temperature after a change for many hours.
I'd expect that the formerly hysteretical resistors would have a much lower T.C. than being falsified by the hysteresis effects.
General Resistors told me, that they let their DUTs rest for 24h on the edge temperatures, and they had totally different results than me on the same specimen.
 
In that sense, Andreas solution is much more versatile, and the temperature can be controlled in a much better manner, and the whole temperature profile (T-loop) can be achieved automatically.

B.t.w., I will soon publish T.C. adjustment experiments on my new LTZ#5 reference, where these hysteresis effects, supposedly caused by exactly these resistors, are strongly dependent on the temperature change rate, and so does the evident T.C.

For a quick selection and characterization of the PWW resistors and the LTZ circuit itself, my dynamic measurement approach was completely sufficient.. the LTZ reference after a few attempts, now has nearly zero T.C.

Frank
« Last Edit: November 26, 2016, 10:16:54 am by Dr. Frank »
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #145 on: December 07, 2016, 01:53:01 am »
Something pop out todays ... unfortunately I'm still dealing with resistors TC characterisation where I found something strange (to me) and I hope I can publish some results in a few days.

It's not the time to build the KX yet ...
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #146 on: December 07, 2016, 03:14:05 am »
Candies!  :popcorn:

I'm doing TCR testing too, but except it being painfully slow, nothing strange so far. Need build separate metal slug thermal unit for faster resistor testings.
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #147 on: December 08, 2016, 01:40:07 pm »
Well really is not strange ...
 
As Dr. Frank wrote somewhere after some thermal stress you need to leave the resistor rest for many hours to make them recovery some thermal caused hysteresis ... only in this case you can get the real TC of the resistor. I found some resistors have more than 20% of TC improvement after waiting 16 hours. I also found this hysteresis to improve with thermal cycles ... than more you therm cycle the resistor than more it gets better.

Unfortunately I don't have so much data to have a clear idea of what is happening ... and collect this will take forever.

Hope I can post some chart in some days.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #148 on: December 08, 2016, 03:17:39 pm »
Quote
collect this will take forever

Just two weeks :)



Data DSVs: Ramp up, Ramp down.
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Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #149 on: December 08, 2016, 06:15:51 pm »
What resistors did you use?
Hermetically or with plastic housing.

Guess with this long time there is some humidity influence.
And some creeping effect if plastic housing.

With best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #150 on: December 08, 2016, 10:45:18 pm »
O men two weeks is the definition of "this will take forever" ... I think with slow ramp up you can go with just 24h.
Lucky you that have the scanner card ... I already finished my budget for the next couples of years so I can measure only one at time.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #151 on: December 08, 2016, 11:23:55 pm »
No scanner card used in this case. Three separate meters are the jedi way. Need to get moar 8.5-digit meters, so I can test 4 resistors together!   :-DD
I tried faster ramps, but it's just too small margins to tell what change from what.
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Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #152 on: December 09, 2016, 04:21:43 am »
If it just for the temperature effect one could go faster and maybe also do a continuous ramp instead of the step like profile. However it is not only temperature that effects the resistors, but also indirect effects, like expansion / shrinking of the PCB which can be in part due to humidity effects. So it is not easy to get a pure temperature effect. Also Temperature gradients can have an influence - this is likely much of the overshoot seen on temperature steps.

A scanner will add some errors - so for highest precision it is better to use the DMM directly. It somewhat depends on the required resolution and noise: one might get away with a good scanner. At least with the slow temperature profiles noise is not that critical - so it is only a possible longer term error (e.g. thermal EMF of the scanner) that is a really problem. On he other side a scanner could reduce some of the thermal EMF errors by reversing the resistor.
 

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #153 on: December 10, 2016, 02:34:53 am »
Since most of my little modules PCBs happen to have same width, I decided to make an hermetical service enclosure for additional thermal testing.
We talked about this wild idea few pages ago, so this will also be used for that.



It's simple copper tube 42mm in diameter, 130mm length with caps. Material of choice is copper, so I can solder it to make gas and liquid tight. This is required to allow submersion into LN2 dewar, while keeping cryogenic liquid out of direct contact with PCB module inside the probe.



Inner tube wall has two slots to support and hold PCB, which just slides in. Caps are easy to solder to the tube, longer copper thin tube is 10mm OD, to have power, signal wiring and cabling escape the dewar and probe PCB.



I'll also test low-noise preamps in this chamber once they ready, to see how temperature affects the noise figures.
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Offline ManateeMafia

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #154 on: December 10, 2016, 03:14:03 am »
Very nice TiN. Looking forward to some real "low thermal" copper put to the test.

Any plans on controlling condensation?
 

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #155 on: December 10, 2016, 03:24:43 am »
It's easy to pressurize inner volume with nitrogen. Just after nice few hours prior bake with everything inside the probe.

First test would be just blank PCB with thermal sensors to measure curves and temperature change speed. Perhaps by using smaller PCB with bit of insulation and internal heater I could also adjust temperature in wider range.
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Online David Hess

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #156 on: December 10, 2016, 06:41:40 am »
I have used liquid nitrogen cooled environmental chambers before with the board exposed without any protection.  Once my boss came in while I was doing a cooling test to destruction and asked how cold it was.  "I do not know because the thermometer only reads down to -199F but since the liquid nitrogen is pooling inside the chamber and the board is sitting in it, I assume -320F."  The precision amplifier and comparator circuit never failed and continued to meet its specifications.

Aluminum electrolytic capacitors (and I assume wet tantalum capacitors but I never tested them) obviously do not function at such a low temperature but the design recognized this and used ceramic and solid tantalum capacitors which had no problem.  None of the common plastic or glass packaged surface mount parts I was using had any issues but I expect that thermal cycling would have eventually broken something.  The total error of the LT1013 class operational amplifiers I was using increased but not in any unexpected way.

For a hermetically sealed design using copper and tin based solder, how quickly does tin pest become a problem?  Is this an application where an antimony or bismuth bearing solder should be used?
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #157 on: December 13, 2016, 02:00:18 am »
So I managed to get my own way of measuring TC of resistors working in a reliable and automatic fashion.

I use what I consider an easy to build but "sophisticated" method to heat the resistor that leave almost
just few seconds of lag from the temperature measurement point and the R variation. As you can see on
the second chart TC curve is almost a straight line  ... this should means temp. and res. variation track very
closely. I still have to check some parameters to prove this method is deftly OK and than I can describe
how I did it.

Anyway apart from heater, the measurement are done with a K2001 in 4W configuration with offset
compensation to avoid thermal EMF to upset readings.

My thermal cycle consists in heating from room temperature to room temperature + 5°K and stay there for
some minutes, than increase other 30°K (and stay at this point for more minutes) and than back to initial
room temperature + 5°K (and rest there for more other minutes). Rump up and down are made almost as
fast as I can. The rump up is 1°K per minute circa and rump down is a little slower than this.

All measurements where done with stable/stabilised room temperature with a max variation of 0.5° C.

I started checking some UPW50 few days ago and I get

  • 10.005,05 @ 26°C
  • 10.006,02 @ 56°C

that is something like ~ 3,2 ppm/K that is also right in the typical specs of the resistors.

The strange thing is that I found something physical is amplifying the TC effect, I observed that after heating
the resistance value always "overshoot" and after cooling down it undershoot. I got more 0.1ppm/°K of
difference if this parameter is measured before or after the rest period (maybe also 0.3 ppm with some
resistors). 0.1 ppm/°K is not much if you are matching 3ppm/°K resistor for the LTZ1000 divider, but I'm still
curious what is it. Anyway if you find a 1 ppm/°K resistor this 0.1 pmm/°K became very important and can
cause significant error in TC measurement (I think this effect will be reduce with low TC resistors but this is
still to be proved).

So the TC of this resistors seems to be a combination fo TC of the wire and TC of some physical stress
applied to the bobbin during heat and cool down cycle with the latter requiring more time to settle down
than just plain TC of EVANOHM.
 
I read Andreas thread about TC of resistor, but I cannot find any measurement where the DUT was leaved
at the new temperature to rest for some hour. Because of this I cannot tell if this behaviour compare the the
chart Andreas proposed in his thread or not.

I found also many of this resistor seems to go down in value after many thermal cycles. This last went down of
20 ppm, but this drift can also be caused my meter that is not stable. I have to remember to check multimeter
offset reading against my calibrator (that has some VHP resistor inside as reference) at beginning and end
of measurement to be sure shift is of the DUT and not by ME.

Any comment is appreciated.

Domenico

PS: just noticed on second chart that measurements gets noisier at the end of heating a cooling process
... so it can also be my measurement technique that is wrong.


PPS: just realised that at the end of the heating/cooling cycle there are a big number of points because
temperature variation is more slower than in the middle of the chart ... so  if we use temperature as X axis
it's normal that it appears to be more noisier at the end of each cycle.
« Last Edit: December 13, 2016, 02:48:09 am by mimmus78 »
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #158 on: December 13, 2016, 06:43:49 am »
Hello,

pictures please.

And I think that the "warm drift" is due to some relaxation effect (or humidity effect) of the epoxy.

With best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #159 on: December 13, 2016, 09:08:41 am »
-- Andreas --
initially I was thinking too to humidity. But I run more than 20 cycles on this resistor and this relaxation effect at begin and end of the cycle is almost exactly the same day after day, from the first cycle to the last one. Unless it's a sponge I guess it cannot be so sensitive to humidity.

-- as for my setup --
it will run all the night to trace the next resistor so I'll try to take some photos tomorrow evening when I will exchange the resistor under test. I hope to have some time to describe why this elementary setup works so well and make a post ... this will be good if you would like to reproduce the same process. In any case, if I will not find the time to do the post, I will just post the photos on your post.

I have some initial conclusions from my initial TC exploration of this UPW50. Almost any value I tested is +2.2ppm to +3.2ppm except for the unfortunate case of the 1K resistor that are all -1ppm.
Still to be determined if they drift apart ... I will check my multimeter in a few days and with all data collected I should be able to track any drift  ...


At the end if I use this three resistors:

  • 2K (+3ppm)
  • 10K (+3.1ppm)
  • 1K (-1ppm)
for the ts divider of the LTZ1000 I get a total error of just a little bit more than 3.2ppm/°K.

This value is than attenuated by a 75 times factor to the Vzener and it become less than 0.05 ppm/°K. This value should be not too much but it's still something to consider in the hole error budget.

I ordered another 1K UPW50 resistor from another supplier in the hope to get one with positive coefficient (it should be here tomorrow).
I think in any case I will assemble the KX reference this week end with what I have ... than maybe I will exchange this 1K resistor in future when I will have one with some positive coefficient.


« Last Edit: December 13, 2016, 09:46:12 am by mimmus78 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #160 on: December 13, 2016, 09:14:41 am »
Andreas: I think I lost from the LTZ1000 thread why the LT2057 was discarded at the end by you, may you just repeat the reason?
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #161 on: December 13, 2016, 09:31:47 am »
Hello,

my UPW50 were all in the range of +0.6 .. +4.8 ppm
(so with a relative large stray from device to device).

https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg503546/#msg503546

with best regards

Andreas
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #162 on: December 13, 2016, 09:50:44 am »
Andreas: I think I lost from the LTZ1000 thread why the LT2057 was discarded at the end by you, may you just repeat the reason?

Hello,

It wasn´t me.
I have 2 references running with LTC2057 (#5 + #6) against 2 references with LT1013A in CERDIP8 (#3 + #4).
Up to now no winner. The lowest ageing drift seems to be on #4 + #6. (with same datecode of LTZ1000A)

If I look closer to the data:
the devices with LTC2057 can be operated at lower voltages.
and have (by accident or systematically?) lower T.C. (before adjustment with R9).

with best regards

Andreas


 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #163 on: December 13, 2016, 09:31:10 pm »
Quote from: Andreas
Sometimes (often?) the hysteresis is larger when having a low TC within a resistor type.

I added another sample but I think you get the point ... actually I measured hysteresis in the first cycle is 33% to 50% of TC.

Maybe we need to change test procedure:

 - What happens if we use only 10°K as thermal cycle with max 1°K per hour of dt?
 - Does hysteresis effect is reduced with lower and slower thermal cycle?
 - If we use fast and slow thermal profile, does resistor settle down to the same value after 24h resting?

To test latter point I was thinking to do:

   - move from t.amb to t.amb + 8 with 1°K x hour
   - rest there for 2 hours
   - move from t.amb + 8 to t.amb + 4 with 1°K x hour
   - rest there for 3 hours
   - move to t.amb + 40 with more than 0.5°K x minute
   - rest there for 1 hour
   - move back to t.amb + 4 with more than 0.5°K x minute and rest there for many hours and check what happens



« Last Edit: December 13, 2016, 10:06:48 pm by mimmus78 »
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #164 on: December 14, 2016, 04:02:48 am »
Alright, long story comes to and end, module was shipped and on it's way to the end user :)

Area around reference chip filled with isolator and enclosed into metal cage for shielding/air draft protection.



Similar on the bottom side.



Final assigned value: +7.1637446 VDC, +/-0.6ppm at +24.0 °C ambient.
Pre-shipment datalog capture proven stability within 0.5ppm over 5°C ambient temperature variation.

Hope we hear from new happy owner in few months, once module make it's way into Belarus  :-DMM
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #165 on: December 14, 2016, 06:51:52 am »
Not nice ... but sure enough stable.
Just realise my thermal chamber used for resistors TC with its 3 cubic centimetres volume is too small for testing this modules :-)

PS: a 3458A is near to begin another journey to his new destination
« Last Edit: December 14, 2016, 06:56:32 am by mimmus78 »
 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #166 on: December 14, 2016, 08:11:52 am »
A not so nice professional look could be an advantage, when it comes to customs.

For the hysteresis, there are several possible effects to cause is. Some of them, like uneven thermal expansion might be influenced by temperature gradients and thus by the speed of temperature changes. But generally I would not expect a big influence of the heating rate. The rate of cooling from high temperature might have an influence, as relaxation processes might get increasingly slow on cooling. So once you are something like 40 K below the last temperature where the system was in internal equilibrium, it may take very long to catch up and may not reach that state even after days of waiting. Fast cooling from high temperature can make a difference - I know it does to the properties of epoxies, when cooling from above 100 C.
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #167 on: December 14, 2016, 10:01:09 am »
For the hysteresis, there are several possible effects to cause is. Some of them, like uneven thermal expansion might be influenced by temperature gradients and thus by the speed of temperature changes. But generally I would not expect a big influence of the heating rate.

I started another very slow test this night 1°K per hour slope and it seems I'm getting completely different values. I too didn't expected so much difference ... let see tomorrow what it turn out after temperature is 10°K up. Actually with 5° K delta is only 0.2ppm/°K VS 1ppm/°K I got yesterday I cannot explain all this difference. Also Edwin explained many times that fast or slow temperature delta should not make much difference with a good resistor.
« Last Edit: December 14, 2016, 10:10:56 am by mimmus78 »
 

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #168 on: December 15, 2016, 03:32:33 am »
Look what showed up today!   :-+

Digikey stuff has been here for a while now, just waiting on resistors.

Thanks again to mimmus78 and TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #169 on: December 15, 2016, 03:37:07 am »
And finally I got around and updated Gerber files to revision B03. Nothing serious, just widen some gaps, thicken few traces and uodated silks/masks and bit of plane pours for more lax DFM. Gerber files hosted the same place as before.

No plans to order/build boards yet though, I need catch up on few other things and build reliable noise measurement setup.
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #170 on: December 15, 2016, 07:23:19 am »
The slow rump up give me exactly the same TC results in the 26-56°C temperature points as the fast rump up so my result are as we all expected.
What was different was that the slow rump up give you the possibility to better appreciate and measure TC with better accuracy at every °K.

The fist 10°K the TC was of -0,38ppm/°K and than it accelerated step by step to -1.6ppm when the temperature was approaching the 56°C.
This has fooled me yesterday in thinking I had completely different data because I made preliminary estimation of TC only on the first 10°K.

I will continue to do experiments ... I'm still not convinced what are those resistance recovery that happens when after a thermal cycle we
leave the DUT rest for many hours at the new temperature. I suspect those recovery are physical compression/relaxation of the resistor
itself and that they also cause the resistor to drift.
« Last Edit: December 15, 2016, 10:37:52 am by mimmus78 »
 

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #171 on: December 28, 2016, 10:56:42 pm »
I've heard member SvanGool got his boards manufactured, using B03 latest Gerber.

He shared this photo with me:



Guard ring bit overly thin, but that shouldn't affect anything much.

Btw, anyone get references based off mimmus78 PCBs going?

Happy holidays everyone!  :)
« Last Edit: December 28, 2016, 10:59:43 pm by TiN »
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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #172 on: December 29, 2016, 12:32:09 am »
You can find TiNs KX-ref PCB Version B03 here: https://oshpark.com/projects/HfKcqjV3 at OSH Park (with TiNs permission).
They are still UNTESTED.

These are the standard 4-layer boards with ENIG(gold)-finish.
The minimum order at OSH Park is three boards, these cost in total $49.80 ($16.60 per board), including standard (international) shipping, excluding any potential taxes or other costs.
« Last Edit: December 29, 2016, 12:35:06 am by SvanGool »
# Don't hurry, the past will wait. #
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #173 on: December 29, 2016, 03:00:49 am »
TiN many buddies received boards, but nobody still built it in public. I'm going to build first sample soon. I received Edwin resistors yesterday (3 sets) ... as soon as I find 2 dammed resistors for the temperature set divider with same tempco I will start.

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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #174 on: December 29, 2016, 10:39:45 am »
Ahh forget to order couple of caps and the TC resistor ... and mounted second op amp reversed!



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« Last Edit: December 29, 2016, 10:43:20 am by mimmus78 »
 
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Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #175 on: December 29, 2016, 11:01:01 am »
Sooner or later you will needs decent enclosure. I used this one
http://www.ikea.com/se/sv/catalog/products/40288354/
It is better than polystyrene box used in past.
Grounding of enclosure is made by cu tape placed over the gasket.
 
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Offline mmagin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #176 on: December 30, 2016, 07:23:38 am »
Well, I'm finally giving into serious volt-nuttery.  It seems like once I manage to obtain resistors I'll probably be building a couple of these.  I'll post updates, and I will probably be interested in the unofficial calibration service.  At the moment, this is all better than the best meter I have, an HP 3457A :)

Is it reasonable to consider the LTZ1000A and precision resistors water washable?  My inclination is toward using entirely water soluble flux, initially washing with warm water and detergent, then multiple rinses of distilled water + isopropanol.
 

Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #177 on: December 30, 2016, 07:46:42 am »
Well, I'm finally giving into serious volt-nuttery.  It seems like once I manage to obtain resistors I'll probably be building a couple of these.  I'll post updates, and I will probably be interested in the unofficial calibration service.  At the moment, this is all better than the best meter I have, an HP 3457A :)

Is it reasonable to consider the LTZ1000A and precision resistors water washable?  My inclination is toward using entirely water soluble flux, initially washing with warm water and detergent, then multiple rinses of distilled water + isopropanol.

3457A is quite good DMM. If you purchase in future 3458A you will know how to operate within few seconds :)
I can hook it to LTZ setup to provide comparison between 3458A nad 3457A. For example K2001 is noisy but stable, 34401A are silent but fluctuating with temperature/humidity.

I will not recommends any washing nor immersing in water. Use IPA only. Clean by brush and small amount of IPA. Some of resistors are sensitive to humidity. LTZ board(s) do not need to be superclean.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #178 on: December 30, 2016, 07:46:54 am »
And here you go. Initial tests with brutal TC estimation tell me all assembly is 0.1 ppm/°K.





 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #179 on: December 30, 2016, 08:17:25 am »
plesa

I used 12K/1K as temperature set poit for the LTZ1000 ... what is temperature delta vs ambient temperature inside this IKEA thermos?
Wondering if it will be too much high temperature during summertime (here gets as hot as 30 degree during summer time).
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #180 on: December 30, 2016, 08:20:06 am »
Anyway during this days I discovered my K2001 is just 5ppm apart from the 3458a on the 10V range (the other ranges are much apart).
Not bad considering last calibration (sticker) is 15 years ago.
 
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Offline plesa

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #181 on: December 30, 2016, 08:36:54 am »
plesa

I used 12K/1K as temperature set poit for the LTZ1000 ... what is temperature delta vs ambient temperature inside this IKEA thermos?
Wondering if it will be too much high temperature during summertime (here gets as hot as 30 degree during summer time).

I'm using same ration sot temperature setpoint (~40°C), but I'm not measuring temperature inside IKEA thermo. That can be interesting.
This vacuum thermo flask is good because it is also humidity tight. With some 3D printed holder and cap over LTZ1000 it is ready for transport.
I do not think the heat generated by LTZ mainly will be problem.
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #182 on: December 30, 2016, 08:57:26 am »
Hello,

you should detect the upper temperature limit when doing final T.C. check (with final housing)
of the LTZ cirquit over the temperature range of interrest.

With best regards

Andreas
 

Offline VK5RC

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #183 on: December 31, 2016, 10:14:41 am »
Re temperature of LTZ in insulated-enclosed environment.
I have been using an old reference board from HP (ex 3458), it is in a metal box with insulation inside the box and some over the LTZ. Tied to the board close to the LTZ (about 6-8mm away) is a Fluke temp probe (brown cable) also inside the box is a linear PSU which  drops from 18 to 15V at about 30mA - so total power inside the metal box is about 0.5W. The metal box is inside a plastic tub (further insulation) see photos below. If ambient is 17-25C (my thermal limits!) it takes about 1-2hrs to stabilise in temp but is  between 30-31C .
Grey cable DC in
Brown Fluke temp probe
Green DC out
Edit; Box is now shut and cables routed through small hole
« Last Edit: December 31, 2016, 10:17:15 am by VK5RC »
Whoah! Watch where that landed we might need it later.
 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #184 on: December 31, 2016, 08:00:49 pm »
If the whole ref circuit is inside a relatively well insulated box, the LTZ internal heater (and the driver transistor) will also work to stabilize the temperature of the whole circuit. It depends on thermal insulation and will not be perfect, but one could expect something like having a circuit temperature at something like half way between the fixed internal temperature and the room temperature. So temperature variation would be reduced by a factor of 2 in this example. To use more of the effect, a slightly higher temperature set point and better insulation could help. Also the amount of insulation directly around the LTZ1000 as an influence - more insulation is not always better.

It is a good idea to have an extra temperature sensor somewhere at the circuit to see if the temperature for any reason is too high. With such an insulated bottle, much of the heat loss is at the top and through the cables.
 

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #185 on: January 09, 2017, 11:03:22 pm »
but nobody still built it in public.

I just got word from Edwin that my resistors have shipped!  I bought enough to populate 3 KX boards, leaving 2 more for future thoughts/lessons learned.  I have all the other necessary components already.

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #186 on: January 09, 2017, 11:15:22 pm »
Almost finished experimenting with mine ... I'll keep it running for some days and than publish what came out.

In all this Odyssey I learned a lot and got some ideas for the next one.

1. Always buffer the reference. I risked to short it many many times in the most not obvious ways. In my case I think this buffer also kinda lowered some noise (but I still have to check measure and confirm this data).

2. I think to get better long term stability and noise is mandatory to add some sort of oven too. This double oven (one in the LTZ and this other) will improve TC and keep resistor at a stable temperature. From my little experience with TC of resistors, keeping resistor at the same temperature will reduce long term drift. But than you have to keep it on always or otherwise the bigger temperature excursions can create more drift/hysteresis to those resistors than the normal t.amb variance.

3. LTC2057 was causing more than 1ppm jumps depending on what power source I was using or if I used shielded leads or not. Replaced opams with ADA4522 and now it's 1 to 2uV delta swapping power supplies or using different leads. The most of the offset was caused by the opamp driving the zener. Changing the opamp for the heater didn't change anything really measurable. Using the same LTC2057 as buffer seems to have a very little influence. Anyway I'm still not convinced about this drift was caused by  LTC2057 ... another LM399 based reference is using the same chip and seems to be not susceptible. Unfortunatelly noise of LM399 is much higher so making such evaluation needs much more care than I really wanted to put in the measurement.

« Last Edit: January 10, 2017, 01:06:51 am by mimmus78 »
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #187 on: January 10, 2017, 07:07:28 am »
3. LTC2057 was causing more than 1ppm jumps depending on what power source I was using or if I used shielded leads or not. Replaced opams with ADA4522 and now it's 1 to 2uV delta swapping power supplies or using different leads. The most of the offset was caused by the opamp driving the zener.

Good to know that the ADA4522 behaves better.
I have solved the EMC-issue on the LTC2057 with a 100nF cap.
(but also use a 22R series resistor and a capacitor in the feedback loop).
https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg846835/#msg846835

With best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #188 on: January 11, 2017, 07:08:32 am »
Well yes slightly better ... I solved susceptibility with Siglent power supply (drift passed from 10uV to 2uv) and apparently reduced problems with leads ... but now I had Idea to test with very short twisted copper ethernet cable (15cm) and I'm getting 10uV down drift. Deftly need to try your caps and resistor for EMC mitigation after buffer. See you in a few hours.
« Last Edit: January 11, 2017, 10:41:41 am by mimmus78 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #189 on: January 11, 2017, 10:02:18 pm »
It's not EMC the buffer just follow what it find on input ... still investigating  :-//
 

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #190 on: January 13, 2017, 01:57:24 am »
First board up and running! 

(12k/1k ratio, Edwin resistors)

Offline splin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #191 on: January 13, 2017, 10:52:32 am »
That's a remarkable meter you used to measure the reference - apparently with maximum and minimum voltages displayed at 7 1/2 digits, uV resolution, but manages to calculate the peak to peak to a further 7 digits, 6.8025031uV p-p. 100 femto volt resolution on a 10V range is quite incredible.

Too incredible obviously. The difference between the displayed max and min values is 7uV. There may be another digit undisplayed so 6.8uV p-p may be plausible even if the .8uV digit is mostly noise. But why would the developers choose to display a further 6 digits of completely bogus resolution? How could the value have been derived?
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #192 on: January 13, 2017, 11:57:54 am »
What's the meter?

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Offline mmagin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #193 on: January 13, 2017, 12:09:24 pm »
That's a remarkable meter you used to measure the reference - apparently with maximum and minimum voltages displayed at 7 1/2 digits, uV resolution, but manages to calculate the peak to peak to a further 7 digits, 6.8025031uV p-p. 100 femto volt resolution on a 10V range is quite incredible.

Too incredible obviously. The difference between the displayed max and min values is 7uV. There may be another digit undisplayed so 6.8uV p-p may be plausible even if the .8uV digit is mostly noise. But why would the developers choose to display a further 6 digits of completely bogus resolution? How could the value have been derived?

Somewhere that programmer's high school science teacher is cringing.
 

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #194 on: January 13, 2017, 12:19:19 pm »
untruncated calculation precision is not uncommon!     :popcorn:

Offline splin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #195 on: January 13, 2017, 01:46:02 pm »
untruncated calculation precision is not uncommon!     :popcorn:

Very true. But in this case what calculation is involved in working out the peak to peak value other than subtracting the minimum from the maximum values? That doesn't create any extra digits, spurious or not, unlike mean and standard deviation calculations.

I'm struggling to think of possibilities but I guess it's conceivable that they could be allowing for the meters own noise by adjusting the maximum and minimum readings by subtracting/adding the meter's known peak noise (adjusted for range, integration time and filtering levels etc.). That could make the peak to peak readings more accurate - on average - but could under/over read true maxima and minima. This seems very improbable though given that the benefits/detriments would likely be very dependant on the statistical properties of the signal being measured.

So where could those extra digits have come from? I'm sure there's a simple explanation but I'm not seeing it at the moment.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #196 on: January 13, 2017, 03:14:47 pm »
dr.diesel
Beauty. Now add some foam protection around both sides of LTZ, drop everything in the metal can, and let it sit for a month or two powered (about enough time to build a DIY thermal chamber for future tempco tests ;) ). Then we can see some data.

I can't say I particularly like these standing way to mount those resistors though. I know why you did it, but not sure if that cause issues due to uneven thermal gradient over resistor body (PCB side leg is much shorter, with much larger thermal mass on it). Usually when using axial resistors, I bend legs in "radial-way" and mount them with body parallel to board.
Maybe if you plan building more boards, you can try that so we can compare?

splin
I'd expect programmers just implemented standard FP math without actually thinking much how real are the numbers, be they down in the white noise, or have real meaning. Doesn't bother me much though, as you already know what is real and what is not.

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Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #197 on: January 13, 2017, 05:36:09 pm »
First board up and running! 

Mhmm,

7uVpp for a source that should have 1.2uVpp.

Which NPLC?
Is it the DMM or the zener?
Does the heater run properly?

with best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #198 on: January 13, 2017, 06:50:14 pm »
So time to publish some result.

It seems I almost sorted out all my problems with EMI and leads and power sources ... now no matter what I do, I do not have anymore super large drift of the output (almost 2ppm before) the max drift by changing swapping all this conditions is now usually 0.1 or 0.2ppm with the larger one of 0.3 ppm when I turn on a programmable power supply.

I will explain all I did in a further post, I think I can live with it for now.

Anyway here is last chart from yesterday when I applied heater caps ... (RMS noise went down of almost 100nV).

The image is very large ... so it's better you open in another window.
The red line at the bottom is RMS noise. 0nV at base of the chart and 250nV at every division, RMS is calculated on last 100 samples.
The tin green line that is my room temperature.
The green dots are the single readings (100NPLC with autozero sync)
The blue line is the median value of the previous 100 readings.
The orange dashed lines are the temperature of last ACAL and the internal temperature of the 3458A (temperature are chart with -10°K to make the chart more compact)
The last black line is internal reference temperature.
The chart is one 10uV large ... so 1.4 ppm.


PS: first drop in the chart is me changing leads.
« Last Edit: January 13, 2017, 06:59:56 pm by mimmus78 »
 

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #199 on: January 13, 2017, 10:10:01 pm »
7uVpp for a source that should have 1.2uVpp.

Yeah, don't think anything of this, it was only a test power up, just to make sure no shorts, it works, I didn't screw up etc.

TiN

Two more boards will be finished today, one I will build like you describe (parallel to the board), same 12k/1k ratio, and the 3rd with 15k/1k ratio, both Edwin resistors.

That will leave two spare boards, I was thinking of building one with off the shelf DK resistors, to demonstrate what's possible without special ordering.  Unsure and taking suggestions for the 5th.

My 3458A mods/SRAMs/re-cap is complete and it's headed to CalMachine's next week for calibration.

I'm also happy to help/provide testing to others.

Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #200 on: January 14, 2017, 03:08:01 am »
Two more complete. 

Had one small issue with the 3rd board, heater wasn't working.  Turned out to have a very small piece of debris in the indicated area shorting pin 1 of U6 and C9, flushed it out with a soft brush and all is good. 

I'm still debating on the enclosure, was originally going to gut my old 731A and install ~3 boards or so, haven't decided yet.
 
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Offline MisterDiodes

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #201 on: January 14, 2017, 04:51:25 am »
Just a head's up and suggestion:  You're using '2057 op-amps which have a tremendous amount of input current noise compared to LT1013, in addition to SMT package which make very good board stress detectors. Beside excess current noise on your extra-long board traces, that additional mechanical stress on the LTZ die caused by AC current noise -can- cause stability problems long term, be aware.  It can also cause die breakdown in extreme cases.  We have seen this effect in other circuits as well, that's why we quit using'2057's in almost all test circuits a few years ago.  The '2057 is not a cure-all for everything, not by a long shot.  It can work, but not really what you want for very long term stability as an LTZ current driver.

See page 18 of the '2057 datasheet, and then start really measuring the current noise compared to a '1013, and you'll see what I mean.  If you want to keep shaking your LTZ die, the '2057 is just the part to do the job!

The -only- recommended op-amp for use with LTZ is the LT1013 (recommended package for best performance is DIP version, ceramic is available too), and there is absolutely no reason NOT to use one, as others have noted here several times.  Your circuit will be just as stable - the slight Vos of the '1013 will have virtually no effect on output.  If you call LT applications, they will strongly advise against the '2057 as well if you are going for high stability, low current noise and low radiated noise on inputs and power busses.  The best defense against noise is to NOT generate it in the first place.

Watch out on those surface mount caps also - not really recommended practice on a precision Vref.  They are very microphonic and will show you board stresses as well.

Just something to be aware of when you mount these boards up.  I would also be careful of 12k over 1k.  That's pretty cool.  We've never had issue with 13k over 1k or even 15k over 1k - plenty of those are perfectly stable after decades.  When I say stable, that means they still don't move a ppm per year.  Which is the realistic limit of measuring any volt-referenced anything at a cal lab.  The overall stability of your LTZ - all else being the same and correct - will be swamped by the crystal lattice stresses in the die itself (and where it was cut from the wafer), and there isn't anything you can do about that except wait. A. Long. Time. for stresses to spread and stabilize.  It will be pretty close after a few days run time, but it takes exponentially long to expose the true story of each LTZ when you're chasing down into low PPM's.

As others pointed out: Resistors standing on end is about the last thing you want for low thermal difference between leads, that could also be a source of that huge noise you're seeing on output.  Of course the LTZ has to be kept covered.  With that flopping around in the breeze like that you will definitely see a lot of noise just from airflow around the device.

After soldering, do your final measurements at least 8 to 12 months out at least and compared to 732b's or 732a's if you have access to several - at least three.  No DMM is good enough to tell you the whole story with these LTZ's. Nulling against a known stable reference will give you a better picture of stability.  The boards you just made are infants and need a -very- long time to become stable again.  You might see some stability after a few months but we cook 'em at least 12 months or longer if the application is critical.

Time will tell.

Good luck!


 
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Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #202 on: January 14, 2017, 06:30:51 am »
Form the pure specs the noise current of the LTC2057 is not that bad: like twice the LT1013 at 1 kHz and maybe even lower than the LT1013 in the sub 1 Hz range as the current-noise of the LT1013 will go up there. However bias currents and possibly current noise could be higher when working at the low 0.7 V common mode voltage.

The problem is that the current noise of AZ OPs is not normal, mainly low frequency noise, but there is also a significant higher frequency background. Performance of AZ OPs depends in a more complicated way on the input impedance, than just giving a current noise number. So depending on the sensitivity of the circuit, there can be extra trouble.

There is just very little to gain in using the LTC2057, but a lot of possible trouble. The LT1013 is perfectly good enough - if you for some reason can't get one form Linear, use the more or less direct replacement from Ti. Before changing the OPs there are other points in the typical LTZ1000 circuit, e.g. temperature regulation at low power (this could be a issue with a 12K/1K divider), the 400 K resistor for TC compensation, EMC, lower sensitivity to the temperature set-point and the thermal design.

You need to cover the LTZ1000 and have a case around the whole board before you can really tell how good it is working. This is especially true with the way the resistors are mounted.
 
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Offline dr.diesel

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #203 on: January 14, 2017, 06:46:11 am »
Great points above, thanks!

The two 12k/1k boards are intentionally borderline, the 3rd is 15k/1k, and the remaining two will be 13k/1k most likely, all with the 2057.

I think then I'm going to build (5) more, but with a layout that will properly accommodate Edwin's 802 series and the DIP 1013, perhaps a few other mods.

Fun fun, now all I need is a Fluke 734,  :scared:

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #204 on: January 14, 2017, 07:51:51 am »
If it is for the boards already made, there is the LT1006 as a single version of the LT1013. So there is an easy way back from the LTC2057 idea. As the chips are relatively far away from the LTZ, the SMD form may not be that bad.

Also not all of the LTZ1000 are equal: the TC without temperature stabilization (but still at the high temperature) can be quite different. To a first approximation the rather good temperature stabilization covers this, but those units with a lower intrinsic TC will be less sensitive to drift in the divider that sets the temperature. This could be important if you compare performance. If you use more of the LTZ1000 at different temperature or current, it might be even worth picking the right ones for each temperature / current combination. Having half the TC for the chip could be as good as half the drift for the divider.
 
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Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #205 on: January 14, 2017, 08:16:50 am »


Hello,

Also not all of the LTZ1000 are equal: the TC without temperature stabilization (but still at the high temperature) can be quite different.

what differences did you measure at the unstabilized T.C. ?

Having half the TC for the chip could be as good as half the drift for the divider.

Where do you get those devices with a halfed value of unheated T.C. ?
Up to now I had less than +/-5% variation in unheated T.C.

With best regards

Andreas
 

Offline MisterDiodes

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #206 on: January 17, 2017, 07:20:23 am »

The problem is that the current noise of AZ OPs is not normal, mainly low frequency noise, but there is also a significant higher frequency background. Performance of AZ OPs depends in a more complicated way on the input impedance, than just giving a current noise number. So depending on the sensitivity of the circuit, there can be extra trouble.


Kleinstein touched the tip of the iceberg here, and after you spend some bench time testing AZ amp like '2057 and their ilk, you realize how close the datasheets come to what Mark Twain was talking about:  "There are three kinds of lies: lies, damned lies, and statistics.:-DD   The datasheets rush to show you the apparently low current input noise of these things, and then try to not really mention what's really going on with transient input current noise happening at the amp's chopper frequency, and then of course at harmonics up from there.

When you look at the input current chopper noise of a '2057 or similar - just from the datasheet - it looks like maybe you still have maybe double the input current noise of an LT1013, but still low.  NOT EXACTLY!  How about 100X to 600X the current noise when you look at those current spikes in detail!  At first you thought you were talking about some pA or nA of current noise - but suddenly you realize you got input current spikes of some uA pounding around your sensitive circuit!

If you look at the LTC2057 datasheet, do you see how the current input noise AT the chopper freq. isn't mentioned a lot?

So you take an LTZ1000 - which wants a QUIET QUIET QUIET and un-eventful current flow, and in return coverts that to a stable voltage across it's zener diode + transistor  Vbe voltage drops - and when you slap a clock-driven, commutation switched auto-zero op amp in there an you get BLAM BLAM BLAM current spikes applied directly to the LTZ die - especially from the inverting amp input.  Those sharp, short current spikes get converted into mechanical stress waves inside the substrate crystal lattice.  It's like you're hitting the LTZ die with a very small, but definite hammer effect of an AC current pulse train.  These disturbances in crystal stress will start at Chopper at frequency, but by the time they reflect and modulate around the edges if the die you'll see detectable stress acoustics up into the low Mhz region.

Not to mention the other thing that happens with AZ amps:  Any trace length and enclosed loop area on the amp inputs will become antennas for noise radiation of what otherwise was a very quiet, beautiful, pristine analog circuit.  Especially if you have "Crop Circles" type traces or "Voodoo Slots" around the LTZ (Not complaining about TiN's board at all, but we've never seen -any- improvement with those types of design tricks - but can and does pickup and radiate noise more when traces are too long and not very efficient layout)  Just when you thought you had a quiet analog board - that AZ amp inputs and power rails will be splattering ~100kHz or whatever chopper frequency hash around the area.  It is a low current, but it can have enough energy to mess up nearby sensitive circuits for sure if you're not ready for it.  In some cases those AZ current spikes over time can drive a crack in to the crystal substrate of whatever they are connected to - usually if there was an edge defect to begin with.

For these reasons above (and because an AZ amp offers virtually no benefit to an LTZ current driver) is why LT does NOT recommend the use of an Auto Zero type amp for an LTZ.  There are other applications for an AZ amp, but this definitely is not one of them.

Remember:  Plenty of workhorse 3458a's out there with ppm / yr drift rates down in the Low-PPM mud, and virtually completely stable for decades without a fuss.  There are no AZ amps, slots or crop circles required.  If the basic datasheet circuit is followed with a good, reasonable, efficient compact board layout - this is very hard to beat for max performance and reliability.  There may be a slight thermal gradient on the non-fancy board, but if the gradient is stable (it usually is inside an enclosure) there is no effect on output.  You keep air drafts away but do not OVER-insulate the LTZ board, which is just as bad as no covering at all (because the heater circuit can't servo correctly in a near 100% thermal-insulated environment).  You select your heater ratio resistors for best performance in YOUR enclosure and application.  After that the majority of the drift rate is dictated by the LTZ die itself, and that is beyond anyone's control after the die is singulated from the master production wafer.  "It is what it is" at that point and the basic long term drift characteristics are locked in for each LTZ die at that exact moment in time it becomes separated from its siblings. 

SO: In general, your Auto-Zero amp board will probably work as we're still talking fairly low current spikes input noise, but the use of Auto Zero amps with high-precision LTZ class circuits is really not recommended engineering practice - ESPECIALLY IF you are connecting a precision, sensitive die directly to the AZ amp inputs.  For instance an LTZ, photodiode, zener, etc.  Also you have to mitigate the chopper noise you're injecting on those op-amp power rails also, which is not insignificant either.  Sometimes you realize that it's more profitable from a noise mitigation standpoint to just perform an occasional drift correction by using a conventional amp.

For the LTZ circuit especially, the '1013 is the best amp to use, and will offer maximum performance up to and including what the LTZ die is going to give you.  It is tailor-made for the LTZ application.

For further reading, I suggest taking a look at Art of Electronics Third Edition, Horowitz & Hill - look at chapter 5.10 and the section on precision op-amps.  Around page 335 it gets more interesting describing most AZ amp architectures - and their test results vs datasheet noise claims.

Also take a look at page 13 here, for a good visual effect of what inputs currents are really doing on a typical AZ-type op amp - this document also describes a test procedure which we've used with some success:

https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/00-14-01-00-00-70-21-03/Chopper-Noise.pdf


« Last Edit: January 17, 2017, 08:04:17 am by MisterDiodes »
 
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Offline MisterDiodes

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #207 on: January 17, 2017, 07:25:01 am »
I just realized - I suggest this thread should possibly be merged back into the main LTZ1000 discussion, for easier reading for future readers and students of precision Vrefs.  This is no longer on-topic of "A Little Jumper"
 

Offline doktor pyta

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #208 on: January 17, 2017, 08:47:46 am »
++

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #209 on: February 14, 2017, 07:46:02 am »
So after being unhappy with first KX I build another sample ... but I have exactly the same problems.

So decided to scope the output and found it very nosier ... LTZ1000 was measured with spring probe directly to the KX out (minimal ground loop). The other two with long ground loop as I I don't want to tear down the LM399 reference. And for the battery I used crocodile ground clip.

Don't know what too think ... but it seems too much noise for a reference.

Even if too early, the modules seems to be in spec at 100 NPCL with less than 1uV p2p noise in the short term.

This is LTZ1000 module:


This an LM399 module:


This is a 3V coin battery:



« Last Edit: February 14, 2017, 07:57:18 am by mimmus78 »
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #210 on: February 14, 2017, 09:23:45 am »

Don't know what too think ... but it seems too much noise for a reference.


This is LTZ1000 module:

This an LM399 module:

This is a 3V coin battery:


Hello,

unless you are having a factor 1000/10000 amplifier in front of your scope you are doing something wrong.
(or you are measuring the noise from your scope).

Try to supply the references from battery + use a metal cookies box (connected to ground of the scope) for your reference.

with best regards

Andreas

 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #211 on: February 14, 2017, 10:21:58 am »
You are right, I was probing directly at KX pcb but I forget to remove leads that where attached to the 3458a.

Now without leads is like this ... it seems better than battery. You cannot ask more from the poor Rigol.


« Last Edit: February 14, 2017, 10:37:58 am by mimmus78 »
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #212 on: February 14, 2017, 04:41:30 pm »
Hello,

previously it was 2 mV/div
now its 5 mV/div
Is it really better than the coin cell?
Or only different scaling?

With best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #213 on: February 18, 2017, 08:01:02 pm »
Yes Andreas you are right (again). Here is output scaled to 2mV.



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Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #214 on: February 18, 2017, 09:51:20 pm »
Hello,

now it looks like noise from a ~60 kHz switchmode supply.
nothing I have ever seen from a reference.

with best regards

Andreas
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #215 on: February 18, 2017, 10:03:46 pm »
Yes I measured same frequency also with battery ... so deftly picking up somewhere. Maybe some coupling with scope power supply.

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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #216 on: February 20, 2017, 06:06:17 am »
It seems I'm not lucky with this KX reference.

At the end I found way to cure the "power supply brand susceptibility" and reduce EMI to acceptable level (less than 0.15 ppm): the cure was to use LT1006.

But I still have huge stability problems. If I swap the zener output on the 3458a (LTZ1000 positive connected to LO and ground connected to positive) I get a difference of many ppm, don't think this is supposed to happen.
Things get even worse if I connect swapped out to K2001. With Keithley multimeter even mV digit is flapping. I think there is some capacitive load problem ...

Anyone has any idea what is going on?
 

Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #217 on: February 20, 2017, 06:40:29 am »

 If I swap the zener output on the 3458a (LTZ1000 positive connected to LO and ground connected to positive) I get a difference of many ppm, don't think this is supposed to happen.

Things get even worse if I connect swapped out to K2001. With Keithley multimeter even mV digit is flapping. I think there is some capacitive load problem ...

Anyone has any idea what is going on?


Hello,

the first sounds like a EMI problem.

you could test for a capacitive load problem by inserting a 100 Ohms resistor in series to the output.
(in high impedance mode of the meters).

Usually Op-Amps can withstand directly about 1 nF. (around 10 m of coax).

a cure to both effects could be done by modifying the buffer OP-AMP similar to my LTZ1047B design.
(series resistor + output EMI capacitor + bandwidth limiting capacitor in the feedback path).

With best regards

Andreas


 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #218 on: February 20, 2017, 07:19:42 am »
The typical LTZ1000 circuit adds some gain to the feedback loop and thus tends to make the output OP even more sensitive to capacitive load than the simple V=1 follower circuit. So it really is a good idea to have some isolation against capacitive load. So even 100 pF could be a problem for that circuit.

How sensitive an OP is to capacitive loading depends on the OP. Some are more sensitive than others. Some start oscillation at 100 pF other can stand 10 nF if the rest of the circuit is good. As a relative low power OP the LT1006 is more like a sensitive one and DS curves are for 10 pF - not the more common 50pF or 100 pF.

So the DMM input could already be too much.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #219 on: February 20, 2017, 09:10:02 am »
OK, with resistor I have following value:

Correct connection: 7.13366
Correct connection with 120 series resistor: 7.13366

Swapped connection: 7.13350
Swapped connection with 120R series resistor: 7.13357
Swapped connection with 270R series resistor: 7.13360
Swapped connection with 1K series resistor: 7.13364

So I guess I need to add a buffer ...

I build a total of 3 of this references, all had the same problem.
With LT2057 and ADA4522 this EMI and capacitive load was even worse.
I remember millivolt difference with LT2057 and this leads swapping.
And for EMI I can make drift it up to 5 ppm by turning on of off a power supply or a led light.

Now the question is, this is happening only to me?


 

Offline doktor pyta

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #220 on: February 20, 2017, 09:23:13 am »
What resistors are You using?
One time I had problems with stability of standard Linear Technology application when I changed resistors from bulk foil to wirewound.
Probably it was due to prasitic L and C.

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #221 on: February 20, 2017, 11:38:59 am »
So the buffer has solved stability problems with keithley multimeter.
Unfortunately not the 16ppm drift by swapping leads. Now I have keitley stable but with the same 16ppm drift (actually 20 on keithley).

@doktor pyta: Resistors are wirewound. I was thinking to this too, but then because I can't remember anyone with this problem in the big ltz thread I discarded this hypothesis.

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Offline Edwin G. Pettis

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #222 on: February 20, 2017, 12:57:55 pm »
For best performance, Linear Tech (and myself) recommend wire wound resistors for best stability and long term performance.  If you have such a high noise field that the resistors might be picking some of that up, you should definitely work on reducing the radiated noise field as it could be strong enough to be interfering with the IC's operation as well.  Getting rid of noise at the source is always preferred to trying to dampen it out in the circuits you are using.  Many sources, such as lamps, power supplies, TVs, laptops, ect., can generate plenty of noise that will be picked up easily several feet away or more and you make a very good antenna yourself.  The only source of noise a wire wound resistor creates is normal Johnson noise, anything else is radiated and picked up.
 
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Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #223 on: February 20, 2017, 03:11:44 pm »
mimmus78

I think Edwin is on the money. But I will gather some data for you tonight with normal/reversal operation on few modules, yet I don't recall any mV-level changes like you mention from past tests.
What connection wire you use? How long it is? What connectors on DMM side? This is the case when photo of setup actually says more than paragraph of text.
« Last Edit: February 20, 2017, 03:16:22 pm by TiN »
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Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #224 on: February 20, 2017, 06:00:10 pm »
OK, with resistor I have following value:

Correct connection: 7.13366
Correct connection with 120 series resistor: 7.13366

Swapped connection: 7.13350
Swapped connection with 120R series resistor: 7.13357
Swapped connection with 270R series resistor: 7.13360
Swapped connection with 1K series resistor: 7.13364

So I guess I need to add a buffer ...

I build a total of 3 of this references, all had the same problem.
With LT2057 and ADA4522 this EMI and capacitive load was even worse.
I remember millivolt difference with LT2057 and this leads swapping.
And for EMI I can make drift it up to 5 ppm by turning on of off a power supply or a led light.

Now the question is, this is happening only to me?

Hello,

no you are not alone.
I also had drift of 3 ppm on a unfiltered buffered output.
https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg846835/#msg846835
Others might have lesser EMI around them (your 60 kHz switchmode problem).

In your case it seems to be no problem with capacitive loading.
In this case the 120 R resistor would be sufficient.
After the 120 R resistor you can put a 100nF capacitor against EMI without influence on stability.

With EMI problems impedances below 377 Ohms (wave impedance of free air) have usually low effect.

with best regards

Andreas

 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #225 on: February 20, 2017, 11:00:48 pm »
If you have such a high noise field that the resistors might be picking some of that up, you should definitely work on reducing the radiated noise field as it could be strong enough to be interfering with the IC's operation as well.  Getting rid of noise at the source is always preferred to trying to dampen it out in the circuits you are using.  Many sources, such as lamps, power supplies, TVs, laptops, ect., can generate plenty of noise that will be picked up easily several feet away or more and you make a very good antenna yourself.  The only source of noise a wire wound resistor creates is normal Johnson noise, anything else is radiated and picked up.

Edwin I don't think I have such high noise, I don't have cheap Chinese stuff turned on during measurement and wifi is far away.
One of previous KX, the one with LTC2057 was drifting 1ppm by just turning on and off an old linear Agilent power supply (E3641A). This power supply should not produce so much crap to shift reference of 7uV.
I measured up to 5ppm drift on the LTC2057 powered one, depending on what I turn on/off ...

The one with LT1006 pass this tests with no measurable drift. Only the bench led light seems to cause 1uV to 2uV drift.

Getting rid of noise at the source is always preferred to trying to dampen it out in the circuits you are using.

I'd like to build some circuit that I can send to calibration lab, I can control what is turned-on in my lab, but I cannot control what is turned on in the cal lab.
Having a circuit that reject this noise is fundamental to me ... I think 1uV susceptibility is acceptable and maybe inevitable, but if we are on the 1 ppm range this can be a notable source of uncertainty.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #226 on: February 21, 2017, 01:29:20 am »
So I removed the buffer for now and got of video of the "Phenomena" with my setup.


Wire is 30cm long copper twisted pair directly connected to 3458a binding posts (so we can exclude it's thermal EMF).

>> yet I don't recall any mV-level changes like you mention from past tests.
Yes never mentioned this because I discovered this problem with swapped leads just few days agoo.
mV changes is with unbuffered version on the K2001 and long wire (more than 1m).

I take the following video with very short wire (same 30 cm) and Keithley.



Even with short leads drift is still 300uV and also noise become way worse.
Counting on what you can see on the video I can say few uV p2p with straight leads (as by Keithley specs) and sort of 100uV with swapped leads.

Here you'll find some photos of the PCB.
In this last sample I used through hole components because I only planned to build one KX so I brought only one BOM few months agoo.
Anyway despite this the same problems where experienced also with fist sample where I used (almost) all components as by part list on TiN KX article.
You can see photo of fist KX sample few posts ago. Exchanged components are the capacitors: in this last sample I used ceramic caps for
the one connected at the 70K resistor nodes, CAP FILM for the other lower values and electrolytic for the three high values (47uF).






« Last Edit: February 21, 2017, 01:44:30 am by mimmus78 »
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #227 on: February 21, 2017, 02:47:48 am »
Just a side note - board should not be flying around like that, you just asking for trouble and cannot honestly expect any ppm-level accuracy in such test conditions.
How about putting board in a small metal box (fixed with foam, not flying freely around)? Tin can from cookies will do, no need anything fancy.

There is still quite a bit of work required to make bare LTZ reference circuit board into robust box like 732A/B, which you can ship anywhere.

I made a video on investigating your problem, and I think I know what it is. Let's see if you know it ;)

EDIT: Uploading video now  ^-^. You guys make me work!  :box:
« Last Edit: February 21, 2017, 03:21:45 am by TiN »
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #228 on: February 21, 2017, 03:25:01 am »
TiN fist KX I put inside this metallic box, with some foam to dump temperature changes.
Foam was covered with capton to prevent leakage as foam can touch some grounding points (you can see some photos on previous post).
I removed some paint from screw-holes to ground all enclosure ... but even this does not worked.
This box has also a LTC2057 buffer, a 15V regulator, fuses, ferrite beads at power supplies cable, ferrite beads at the binding posts cables, etc etc.
But all this was useless and didn't fix this "phenomena".



« Last Edit: February 21, 2017, 03:36:33 am by mimmus78 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #229 on: February 21, 2017, 03:29:01 am »
EDIT: Uploading video now  ^-^. You guys make me work!  :box:

Time for some F5 raffica at TiN youtube channel ...
 

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #230 on: February 21, 2017, 03:45:31 am »


Here we go. :)
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Offline mmagin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #231 on: February 21, 2017, 06:44:38 am »
Is the power supply negative lead connected to earth ground and the 3458A LO terminal connected to the Guard?  I can certainly imagine that having an effect when the leads to the 3458A are swapped :)
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #232 on: February 21, 2017, 08:21:03 am »
Well it seems pushed on TiN 3458a, but it was/is not on mine.

Anyway this isn't the first reference I do this test and they always show 1ppm circa of difference not 30ppm.

« Last Edit: February 21, 2017, 08:39:24 am by mimmus78 »
 

Offline Alex Nikitin

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #233 on: February 21, 2017, 08:59:18 am »
I've tried today a reversal on my LTZ1000 reference in the lab, connected to the HP3458A by about two meters of a screened twisted pair cable, the screen is connected only to the Guard terminal on the HP meter. The meter is on a different bench (hence the long cable). The reference is built on the AD5791 1ppm DAC evaluation board from AD. It is unscreened, the board is sitting in the open with only some bubble wrap around it, supplied from a bench PSU. I could not reliably detect any difference in reversing the leads, positive and negative values were the same down to ~1-2uV, in the noise of the system after some small thermal variations settled. I know that my LTZ1000 reference is not ideal (I have a tempco ~0.5-0.8ppm/C due to some cheap SMD resistors used, only the 110 Ohm current setting resistor is a decent WW Ultrohm), but there is no instability, no problems with the polarity reversal and no "jumps". Very quiet though not very temperature stable.

Cheers

Alex
« Last Edit: February 21, 2017, 09:02:28 am by Alex Nikitin »
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #234 on: March 01, 2017, 01:29:46 am »
Few updates on my third KX.
I added back the buffer using the same schematic that Andreas posted, plus I added a 1k resistor and a 100nF cap between the zener out and the buffer input.

After 1 week and 200 hours ~ of operation it's still stable at 7.13366.
If we add a further digits its 7.133662 and this 7.133662 was the initial Vout it stabilised the first day (when the reference was enclosed in the foam).
If we stretch a little bit my measurement results with the 3458a, the max delta V measured during this days using: same leads, same power supply and a delta temperature not more than 5°C was not more than 0.2ppm. So if I don't change the measurement conditions this slapped together sample seems enough stable to the point I cannot reliably measure any drift with equipment I have.

Kinda puzzled now ... never wanted him to survive more than few tests, but it's alive and until it will show to be stable under controlled conditions it will survive.

Here we go. :)

I have some more weird results that are driving me to the EMI direction again, but I need to do more experiments to be sure ...
TiN any news about explanation of the drift?

« Last Edit: March 01, 2017, 01:40:13 am by mimmus78 »
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #235 on: March 01, 2017, 05:23:27 am »
In case I shown on video it was a ground loop problem. 3458A, gpib cables network, other equipment are making a path for ground currents, which easily upset sensitive direct reference output.
Keithley 2304 is particularly bad in this point, as it's has very weak isolation to earth.  If you can repeat reversal measurement with battery (even just two 9V square cells with do fine for quick test) and reversal errors gone - same case for you.

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Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #236 on: March 01, 2017, 06:07:47 am »
It should not be a DC ground loop problem: The DC output impedance of the LTZ1000 circuit is very low. The OP in the LTZ1000 circuit already make it a kind of buffered output, capably to drive several mAs of current if needed. Output resistance is mainly given by the wire resistance and thus is more in the 100 mOhms range.
Thus is would take a substantial (e.g. upper µA range) DC current to cause such a large error on reversal. In this loop there both the isolation of the supply and the 3458 are in series. So even a grounded supply would not be a problem.

The problem is more an AC ground loop and sensitivity to EMI. Also capacitive loading to the output is different. The LTZ2057 OP is much more EMI sensitive than the LT1013/LT1006 and also possibly sensitive to output capacitance.
 

Offline TiN

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #237 on: March 01, 2017, 06:11:30 am »
How is the capacitive loading is different, as same board and connections used in both battery-powered and PSU powered cases?  :scared:
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Offline Andreas

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #238 on: March 01, 2017, 06:21:04 am »
Make the following test:

Measure capacitance from +Input to earth ground / and or guard
Measure capacitance from -Input to earth ground / and or guard

Any differences?

With best regards

Andreas
 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #239 on: March 01, 2017, 06:29:19 am »
When battery powered there is a low capacity from the supply side to ground, whereas the mains powered supply will have a considerably higher capacity to ground.

The capacitive loading seen by the reference output has two parts: the obvious one is the capacity between the DMMs inputs - this does not change.
The additional one is from the reference output to ground (especially that of DMM input to PE) in series with the capacitance of the supply side to ground. This changes if you swap the DMM inputs.

The long wires to the lab supply and the lab supply itself can introduce some RF noise and background to the capacitive ground loop. So things should be worse with the ref + connected to the negative input.
 

Offline julian1

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #240 on: March 01, 2017, 10:28:56 am »
What happens if you don't use twisted pair - is it worse?

What about using ferrite beads/chokes on the leads going to the meter?

For another data-point (ie maybe unrelated) I have/had significant emi issues with my ltz1000 -  both breadboard and basic pcb implementations. I varied my design from the datasheet and used dual-rail op27 and not the ltc1006/13. I wondered if there might be something in the choice of op-amps - and if the r2r input/output stage of the lt op-amps might help supression.

Things that somewhat helped (or reinforced the conclusion of emi) - was removing the signal diode on the output of the op-amp that ensures positive output for zener startup. I suspect it has some influence as an RF rectifier and added a varying output bias. Also, isolation in a metal can.
« Last Edit: March 01, 2017, 10:44:21 am by julian1 »
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #241 on: March 01, 2017, 11:35:37 am »
OK ... taken some more measurements and get still inconsistent results.
Sometime things get better, sometimes sensibly worse.

For example some days ago I checked reversed output with batteries and it was OK.
Today I have drift and instability even with batteries, there should be something different I do that screw up.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #242 on: March 01, 2017, 09:23:25 pm »
GOTCHA!!!

If I put battery pack on the antistatic mat with reversed connection I have the problem. If I move battery pack away no problem even with reversed connection.

Generally anything that touch antistatic mat (included shielded leads) screw the things few ppm.
This explain also why I had so inconsistent measurements during last two months.

I already checked grounding of the mat (was 1M ohm), outlets and instruments and it was ok.
I will do some more checks when I back to lab this evening.
 

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #243 on: March 02, 2017, 03:57:51 am »
The diode at the output of the driving OP should add little more sensitivity to capacitive loading, but not much. At a DC current of about 5 mA the effective resistance of that diode is only about 5 ohms.

The LT1013 does not have such an unusual input stage (only single supply, not rail-rail). If at all the low bias output stage could be a problem, but with the 5 mA of DC current it is working as a class A stage.
One possible measure to improve EMI and load capacity tolerance might be an RC (e.g. 10-100 n and 100-220 Ohms) element to GND at the output. A ferrite bead could be a good idea too.

The LTZ circuit from the DS is made for an instrument internal reference, not really to drive an external output and thus handle capacitive loading, possible ESD and RF noise. Also remember that to much load, so that the voltage drops well below 7 V would cause the heater to go for a higher temperature and this way possibly upset the reference and possibly even cause permanent damage if there is no sensible limit to the heater current.

The OP27 and similar OPs have quite a high current noise and also bias drift and are thus not the best choice for a high source impedance (about the typical 70 K resistor).
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #244 on: March 02, 2017, 11:23:14 am »
Made some more tests and as far as I keep KX reference, his metal box and leads far
away from grounded mat I always get consistent measurements.
My antistatic mat cover almost all workbench so it just happened some months later
that I tested KX without any of this part touching it.

With this precautions I can use different power supplies or different leads and get always
the same output +/- 1uV.

It even get's better if I use the Agilet e3641 power supply (instead of the Siglent). Output is
identical as with batteries and also reversed leads test produces the same and stable Vout.

EMI also is now ok. With the buffer, some ferrite beads at Vin and at the "binding posts" and
the metallic enclosure seems to works reasonably well. The max drift I can produce
now by using normal lab equipment and appliance is just 0.5uV.

Still have to read/study what you all write back there to check if things can be improved to
get also "mat" immunity.

Anyway I'm starting to like where I'm going with it. I wonder what can be the experience
with a 732a or 732b or any other serious stuff ...
 

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #245 on: March 02, 2017, 05:40:48 pm »

One possible measure to improve EMI and load capacity tolerance might be an RC (e.g. 10-100 n and 100-220 Ohms) element to GND at the output. A ferrite bead could be a good idea too.


Excellent!. I bodged in a low-pass filter immediately after the diode R=100, C=100nF (I think that's a cutoff of 15kHz). Waving my hand over the unshielded board used to produce a 500uV output change. It's now very difficult to detect anything that could not be attributed to air circulation. The 12k/1k temp-set resistors are currently non-tempco ones so I'll wait to replace those before doing more tests. It really deserves a better pcb with gnd returns at this point.

Quote

The LTZ circuit from the DS is made for an instrument internal reference, not really to drive an external output and thus handle capacitive loading, possible ESD and RF noise.

The only capacitive load I am aware of is the multimeter probe tip/grabber and front-end circuitry.
 
Quote
The OP27 and similar OPs have quite a high current noise and also bias drift and are thus not the best choice for a high source impedance (about the typical 70 K resistor).

Thanks, I followed your previous advice on this, and they were replaced with opa277.

Offline Kleinstein

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #246 on: March 03, 2017, 03:04:45 am »
It only takes a few 100 pF at the output to upset the LT1013. The typical LTZ1000 circuit can be even more sensitive than the simple times 1 impedance follower. A DMM can have a significant input impedance, so is a certain length of wire. Even if not oscillating extra ringing from externally injected noise can cause trouble.

The 100 Ohms and 100 nF not only function as a filter, they also represent a significant load to the OPs output and this way reduce the gain a little. This helps to improve stability at high frequency. Some amplifiers use this to stabilize the output with difficult loading.

I remember an instrument (Lockin amplifier) which had just an OP to drive an output, that could not even tolerate an 2 m coax cable on that output.  :palm:
 
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Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #247 on: March 05, 2017, 11:31:18 am »
So it's time to show you some data with this KX003.
Reference (or 3458a) has drifted up 0.3ppm since first day but it's still stable.
I run a 12h stability test, trying to keep temperature constant except my Daikin as a strange concept of constant temperature and it drifted 1°C in a day.
Notice there is some drift due to temperature, this should be 50% due to KX TC and 50% due to 3458a TC.
This KX seems it needs a 250K as compensating resistor ...
 

Online David Hess

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #248 on: March 05, 2017, 03:01:54 pm »
It only takes a few 100 pF at the output to upset the LT1013. The typical LTZ1000 circuit can be even more sensitive than the simple times 1 impedance follower. A DMM can have a significant input impedance, so is a certain length of wire. Even if not oscillating extra ringing from externally injected noise can cause trouble.

The 100 Ohms and 100 nF not only function as a filter, they also represent a significant load to the OPs output and this way reduce the gain a little. This helps to improve stability at high frequency. Some amplifiers use this to stabilize the output with difficult loading.

I remember an instrument (Lockin amplifier) which had just an OP to drive an output, that could not even tolerate an 2 m coax cable on that output.  :palm:

I never noticed the LT1013 being that sensitive to capacitive loading but at the end of Linear Technology application note 148 is a description of how to use an RC snubber on the output of an operational amplifier so that it can handle a capacitive load better; set R to the reactance of the load capacitance at resonance (measured) and the reactance of C to like 1/10th of that.  If the load capacitance is poorly defined, then add a shunt capacitance to swamp it out.
 

Offline mimmus78

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #249 on: March 17, 2017, 09:55:42 am »
So today my KX reference gets one month old.
Measurements drifted +1ppm in respect to my 3458a since day one.

Also other two LTZ1000 references has drifted +1ppm in last week so I think this is most probably due to some hysteresis of my 3458a than the drift of the references itself.

As bonus I enclose also here the noise floor of the KX reference + the buffer (thanks to Andreas for sharing the schematics, booth of the buffer and of his 10000x preamp).
Considering my setup I think it's in spec with 1.2 to 1.4 uV p2p noise.


« Last Edit: March 17, 2017, 10:02:28 am by mimmus78 »
 

Offline ap

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #250 on: March 17, 2017, 09:03:38 pm »
Unless you have the 3458A running all the time (and even then) the 3458A is not good enough to verify a LTZ1000. I have seen that many times. That does not contradict 3458A spec, but even if you switch a 3458A of and on shortly thereafter, you see some hysteresis (at least if you have not reduced the LTZ internal temp.) There is no way arround a precise voltage reference...
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Offline Dr. Frank

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Re: [FT] LTZ1000A fairy-tale, or the story of little jumper.
« Reply #251 on: March 17, 2017, 10:11:56 pm »
Unless you have the 3458A running all the time (