Author Topic: Project KX : DIY calibrator / reference source/meter  (Read 129099 times)

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Offline jlmoon

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #100 on: June 24, 2014, 07:35:55 pm »
I have a antistat pad full of LTZ1000A's but no fixture to hold them.  :(
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #101 on: June 24, 2014, 07:50:43 pm »
I wish to be as lucky. So far killed my only one ltz, and need to buy 5 more to make units. More VHPs should come in few weeks too.
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #102 on: June 25, 2014, 03:03:13 pm »
I belive that question regarding cost was already replied just about here.
My operation range for VREF is +20 to +50°C, just in case, with passive thermal control only (isolation).

Cost gap across tolerances in prototyping qty was not that much, so since we paying big bucks for resistors anyway, just went with 0.01 Abs Tol.
Also Z201 for some ranges/tolerances was actually more expensive.

P.S. you can also see higher spec parts, which are a magnitude (10 times, that's correct) pricier :). Those will be my reference resistors for calibration, along with VHP202Z's.
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Offline KC0PPH

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #103 on: June 28, 2014, 12:19:05 am »
just curious Tin would you be willing to sell one of your proto boards that has been built and tested?

I am working on something similar but do not have anything near what you have for test gear and would like to possibly get my hands on one of your units. I am willing to pay and even throw you one of the SMU's once they are done.

As for a quick update I have the ps running and they look good using HP 6.5 digit meters. Next step is to design the measure part of it and then put in the feedback parts.

If you can not provide an assembled tested unit could you provide a kit with the required parts (i cant seem to order the resistors without spending several hundred dollars for just a few (when they are $30 each...))
 

Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #104 on: June 28, 2014, 01:41:31 am »
They have few mistakes, and still need test.
Need to receive rest of resistors and buy LTZ's.

Hope to get something up an and running in few weeks.

You can follow up and see current items progress via my project tracker.
« Last Edit: June 28, 2014, 05:04:10 am by TiN »
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Offline andy_silicon

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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #106 on: July 05, 2014, 08:43:31 am »
Yes, it's borked...

LTZ1000A die photos..





Die looks like to be glued to package case, not soldered.
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Offline branadic

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #107 on: July 05, 2014, 09:37:58 am »
Quote
Die looks like to be glued to package case, not soldered.

We could have told you that without opening your LTZ ;)

Typically the die is glued with silver-filled glue to the surface of the package und additional fixed with underfill (the yellow stuff)
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Offline Andreas

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #108 on: July 05, 2014, 09:51:14 am »
Quote
Die looks like to be glued to package case, not soldered.

We could have told you that without opening your LTZ ;)

Typically the die is glued with silver-filled glue to the surface of the package und additional fixed with underfill (the yellow stuff)

I think that the non-A type will use silver filled epoxy. (gives good thermal conductivity).
On the A-Type I would expect hollow glas filled epoxy to reduce thermal conductivity.

@TiN: do you have the possibility to check whether I am right with my assumption?
Or how is the thermal isolation done?

With best regards

Andreas


 

Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #109 on: July 05, 2014, 10:24:51 am »
I don't have dead non-A LTZ to open :)
Will try to make a better photo , but we all know result already, so its just curiosity.

Time to build something, finally. I decided to cook revision for VREF pcb anyway. Also one version for LM399, as it happen that I have few 399s from dead KEI 2001 and one new.
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Offline branadic

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #110 on: July 05, 2014, 10:55:10 am »
Quote
On the A-Type I would expect hollow glas filled epoxy to reduce thermal conductivity.

And what about substrate potential? In the case you mention the substrate would be floating. In many cases the die is connected to a defined potenial. If we take a look on the photos this is not the case with the LTZ.
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #111 on: August 19, 2014, 04:42:40 pm »
Got more VHP202Z, VHP203's, now have enough to make 5 VREF boards finally.



Also just received today 3 x LTZ1000A and 2 x LTZ1000's from Linear website order.
Interesting note, A version made in Malaysia, while non-A is from Phillipines. Datecode of first is 1424, non-A is 1416.



Assembled two boards first with few corrections, one with A, second non-A.



Put VREF into plastic box, which put into antiESD bag, and powered non-A from KEI 2400, readout Vout on KEI 2002.
Will left overnight, will see if it drifts.

Current consumption of whole board stabilizes around 10.528 mA at 12.000 VDC provided, according to SMU.

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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #112 on: August 21, 2014, 12:50:16 am »
After fixing all mistakes , it finally works :)



LTC2057 + LTZ1000CH (12K + 1K resistors for temperature setting)
Power source +12 VDC, consumption 32??

2 hour log from 34970? (6.5 digits)



Sags and spikes are due SMPSes working nearby, dirty lab environment.

Insulated fine when got home, repeated measurements...
Voltage output monitoring by 8.5digit Keithley 2002, 10 NLPC, Filter AVG(20), autozero sync enabled.
Power source - Keithley 2400 SMU, 15.000VDC, current after few hours stabilized at 29.3mA
Ambient temp - +26°?

Overnight data collection: maximum - 7.1296886, minimum 7.1296773, total range less than 1 ppm  :-DMM



Overall look of prototype board after all corrections:



RN55C 10K resistor above goes to inverting input of heater control LTC2057
Resistors 120, 13K0, 1K00 - Vishay Precision Group Z202 0.01%
Resistors 70?000 - Vishay Precision Group VHP203T 0.1%
?? - Linear LTC2057
U3 - MAX6610 thermal sensor IC
Bulk caps KEMET , film SMD caps - Vishay



Look on resistors. Cost: per part.
Lead time of resistors got about ~3 month.



Back side view. 6-leg bug near LTZ - second MAXIM MAX6610



View from side



Stupid mistake on pinout for power transistor, collector and emitter were swapped.
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Offline Vgkid

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #113 on: August 21, 2014, 12:55:13 am »
That is impressive, and a prety board as well. Now to burn them in.
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #114 on: September 24, 2014, 04:23:19 pm »
Got an nice set of metal boxes from IKEA. They solderable perfectly.
Smallest one fits one reference board perfectly.



Soldered two SMAs (LTZ zener negative and LTZ zener positive, outer case - power ground) and BNC (input power source)



Assembly mockup



Enclosed reference with connections and T-SMA adapters



Power source and measurement of LTZ module output.



I collected one week long data from this exact same module board, so will repeat test and see how is lowspeed noise.
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Offline macboy

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #115 on: September 24, 2014, 06:25:43 pm »
With all due respect, I don't think that you can characterize the drift and noise in a LTZ1000 -based reference using a multimeter that itself uses a LTZ1000 reference. You will need something several times better than what you are trying to measure.  For a LTZ1000 ... well ... that means basically a JJA.
 

Offline Dr. Frank

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #116 on: September 24, 2014, 09:07:56 pm »
With all due respect, I don't think that you can characterize the drift and noise in a LTZ1000 -based reference using a multimeter that itself uses a LTZ1000 reference. You will need something several times better than what you are trying to measure.  For a LTZ1000 ... well ... that means basically a JJA.

Hello macboy,

that's an interesting issue you critically pose here..., it's a very basic question about any kind of  "standards".

Well, I think, you are not right that a JJA or something much better than an LTZ is necessary..

That's the famous problem described by: " A man with one clock knows the time, a man with two clocks is never sure, a man with three clocks..."

OK, let's get "scientific", by shifting your objection one level upward:

How is  it in principle possible, to specify the uncertainty or stability of the very best standards, if there do not exist any better ones?

How can metrologists even conclude, that a JJA standard itself is uncertain to better than 1e-16, if there exists no better quantum volt standard?
How can they conclude, that the Cs fountain clock is stable to 1e-15..1e-16, if there exist no better clocks?  (OK, today we already know better ones, but how do we judge these, again?)
 
How did the metrologists find out, that the kilogram prototype in Sèvres, France, thought to be "absolute", is in fact unstable to 2e-8 in 100 years, and that all the other, identically made ones, are consistent?

Very simple, they have always compared two, or more physically identical standards, against each other.

The idea is, that if they have an intrinsic drift or uncertainty, they will presumably drift apart, and the uncertainty is then defined as being about half, or something like sqrt(N) - statistics of the drift against each other.

The more different samples of the standard in question you have, the better the statistics is, and the lower the probability, that the whole entity does not drift in the same direction.
That's the purpose also of ring comparisons, btw.

Therefore, comparing the homemade LTZ1000 reference against the Keithly one, will give a good indication of the (combined) stability, at least.

As the Keithley reference is characterized by its stability specifications, for this case of relative measurements, its 10min and 24h stability, the Keithley instrument has a more profound weighting.

Therefore you can at least judge the DUT exactly by these Keithly specs, or even better, if the drift between both is less than the Keithley spec.

I admit, having 3 references (including the DUT), would allow to judge, which one drifts outside the entity, and 4 or more allow to do a better statistical analysis.

Also, the LTZ1000, like the LTFLU in the 732B, Fluke 57x0 instruments, are known to have tendentiously a  negative drift (on the order of less than -0.7ppm/yr.) , see correspondent specifications or analysis. But this is not important in this case of short to mid term drift measurement.


Myself, I have 4 different voltage references, which I monitor for now about 5 years: 2 homemade LTZ1000, one LTZ1000A in the 3458A, and 2 stacked SZA263 in the 5442A.

This whole group did not drift apart more than +/-1 ppm over all these years.

Therefore, I have quite a good evidence, even without the aid of a JJA, that each of my 4 references are stable to a level of <1ppm/yr.
(If I would have access to a JJA, I could determine the absolute values of my references, but that's secondary.)

In the same manner, I was also able to make some short term  stability (noise) measurements in relation to my 3458A, which had been specified by HP concerning this parameter.
So I could tell, that the 5442A was a little bit less noisy than the homemade LTZ1000 references, each of them on an order of <0.2ppm, and that an old Fluke 332B was 10 times noisier.

Therefore, it may sound weird, but this bootstrapping procedure, by comparing 2 or more virtually identical references, actually is a well accepted metrological practice to determine (estimate) their stability figures.

Frank
« Last Edit: September 24, 2014, 09:42:27 pm by Dr. Frank »
 

Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #117 on: September 25, 2014, 12:26:18 am »
Also for noise testing having JJA is not required as well. What is more important, is to have gear with own noise levels / sensitivity significantly lower than DUT. Famous appnote from Jim Williams stands to this point.
I am planning to build similar amplifier myself.

Another reason why I built can test box, is to test variation between multiple VREFs using different resistors.
I will use bigger box and put 5 VREF modules. Enclosed metal can serves two purposes per idea:

* Have uniform thermal distribution inside a box with zero airflow
* Reduce noise pickup from gear around the room

I think IKEA cans with embedded soldered coax connectors will serve both pretty well.

Test units are:

* A. LTZ1000A with VHP + Z202
* B. LTZ1000 with VHP + Z202
* C. LTZ1000A with all VHP
* D. LTZ1000A with Fluke wirewound resistors
* E. LTZ1000 with low-cost 10ppm PTF56 resistors
* F. LTZ1000A with generic resistors

Also there are options with modules with film capacitors and ceramic X7Rs, with different opamp, LTC2057, LT1012, LT1097.
So it's lot of various configs we can check against two meters (calibrated Kei2001 and unknown Kei2002)

REF A, data from 1 week ago, after which unit was sitting non-powered.



REF A, this night test in metal can. Fact that after initial warmup output voltage recovers back within 0.3ppm is pretty good indication.



I have small TEC module as well, which I might use to vary box temperature, but that's rather later "todo" item, than requirement now.

Expect to receive my custom Vishay resistors tonight :)
« Last Edit: September 25, 2014, 12:27:56 am by TiN »
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #118 on: September 26, 2014, 01:41:43 am »
Finally got my goodies :)

1Meg :)



Matched TCR set with three 0.005%



CSNG for current transduser.



LEM IT600 + VPG



« Last Edit: September 27, 2014, 06:07:41 am by TiN »
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #119 on: September 26, 2014, 04:15:38 am »
Initial measurements with K2001.

1.9K



95K



1M

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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #120 on: September 27, 2014, 06:12:57 am »
More measurement data on K2001. Captured 200 samples for every resistor, plus overnight on 1Meg.
Also checked 19K with K2002 with 1NPLC and 10NPLC. Can see difference to Model 2001, even at same 1NPLC and resolution.

Two resistors data - CSNG 2R5 0.1%, 1NPLC 4Wire with nulling on shorted kelvin probes.



Overnight 1Meg.



19K from 321217 set, both K2001 and K2002 data.



Now finally time to build some more circuits and layout some more PCBs :)

« Last Edit: September 27, 2014, 06:14:57 am by TiN »
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #121 on: October 29, 2014, 11:06:24 am »
Got some goodies today, this time for digital side.

It's some overkill FPGA chips from one of eevblog members here :)

New and packed in dry sealed package, waiting for PCB.
I am considering to try Linux on NIOS, for data collection and interfacing like LAN, display.
Also modern multigb SD cards are cheap today, which will give pleeenty of datalog storage.
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Online awallin

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #122 on: October 29, 2014, 07:35:53 pm »
Looks like an interesting project! Despite activity, roadmap, and gant-chart on the xdevs-website it's a bit hard to grasp what has been completed, what is currently being worked on, and what hasn't been started at all yet.
If someone could write a brief summary on the website or here about the current status I think that would help potential contributors get on board with the project. That probably needs to be repeated every 3-6 months as the project ages.

It's some overkill FPGA chips from one of eevblog members here :)
Are you really going to build your own fpga-board? I would have thought there are many ready made dev-boards (even open hardware ones) to choose from. Same goes for the uController part. In fact why not run the uController as a softcore in another identical fpga dev-board?
As for the display and front panel I would definitely go with touch-screen and no mechanical (=expensive) buttons and dials.

The digital side of things will probably evolve much faster than the analog side, and by the time you have the analog side ready (6-XX months from now??) there might be new and better/cheaper fpgas and uControllers around. I hope you are designing all the analog boards with isolated digital IO so that the controller side can be swapped out easily?

AW
(I probably too busy with my own projects to really contribute here - but following progress with interest!)
 

Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #123 on: October 30, 2014, 05:04:20 am »
Good points, there is definitely room for improvement for newcomers. I will try to improve that side to make progress/updates more clear.

As of FPGA , yes, mainly due to a cost reason. Any beefy enough FPGA kit capable of running Linux will cost a little fortune, while I can get memory, PCBs and parts for a good price here. For display it's just graphical VFD so far. Keypad is an undecided point yet..

I still have references burning in and working on ADC/DAC boards. All modular design on separate boards for now, so everything is swappable/configurable flexibly.
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Offline TiN

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Re: Project KX : DIY calibrator / reference source/meter
« Reply #124 on: November 06, 2014, 04:26:13 am »
Was making 7V>10V/20V voltage convertor on LTC2057HV and decided to add pair of LM399's just for fun.
Compared to LTZ, it's much simpler to add these. Also I do have few extra LM399 from broken Keithley 2001's and few new ones.
Will be interesting to compare those to LTZ on same conditions, board size.

Schematics

Doing layout now...

Also will make PCBs similar to Keithley 8610 4-w shorting plug, to test meters.

Still thinking about idea of converting K7001 into calibration switch box, with custom reference/resistance/current add-on card
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