Author Topic: Ultra Precision Reference LTZ1000  (Read 1333254 times)

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Offline Edwin G. Pettis

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Re: Ultra Precision Reference LTZ1000
« Reply #2425 on: November 06, 2018, 01:43:49 am »
To exe, reply 2430, the LT1013 was specifically designed to work with the LTZ circuitry, the LT1006 is very similar to the LT1013 being a single op-amp but is not exactly identical.  The LT1013 (from LT) is still the best op-amp to use with the LTZ circuits.
« Last Edit: November 08, 2018, 05:24:52 pm by Edwin G. Pettis »
 

Online Kleinstein

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Re: Ultra Precision Reference LTZ1000
« Reply #2426 on: November 06, 2018, 04:05:26 pm »
The LT1013 is single supply, so it can work well at the low (e.g. around 500 mV) input level, without a negative supply. The single equivalent is the Lt1006 (the lt1005 is an obsolete regulator).

The LT1001 is other wise OK , but not single supply and would thus need an extra negative supply and provisions to get a defined start-up sequence. It might still be OK for the negative reference circuit, but even there during startup the common mode voltage can be quite close to the negative side.

Also the OPs are not that critical to the performance, so no need for a really high performance OP. Just from the data-sheet performance even an LM358 could work reasonable, though I would still prefer the LT1013, but no real need to get one of the better grades. Just like with the resistors the drift from the OP is attenuated by a factor of some 200.
 

Offline Andreas

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Re: Ultra Precision Reference LTZ1000
« Reply #2427 on: November 06, 2018, 07:45:39 pm »
Hello,

the LT1013 has better open loop gain (against LT1001)
This is essential especially for the zener current regulator.

with best regards

Andreas
 

Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2428 on: November 07, 2018, 03:00:35 pm »
Attached are the cad files for front and real panel of the Hammond case.

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Offline Fastah

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Re: Ultra Precision Reference LTZ1000
« Reply #2429 on: November 07, 2018, 06:38:57 pm »
Sorry to say that, but all boards have been sold.

-branadic-

Hi
I'm interested for 3-5 boards. Are you planning to make more boards for sale here on forum?

Thank you
 

Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2430 on: November 07, 2018, 09:26:24 pm »
In short? No :)

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Online exe

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Re: Ultra Precision Reference LTZ1000
« Reply #2431 on: November 08, 2018, 08:40:53 am »
the LT1013 has better open loop gain (against LT1001)
This is essential especially for the zener current regulator.

Why is this essential? To reduce noise?

Just from the data-sheet performance even an LM358 could work reasonable, though I would still prefer the LT1013, but no real need to get one of the better grades. Just like with the resistors the drift from the OP is attenuated by a factor of some 200.

Could you please elaborate how offset is attenuated? I thought offset only amplifies as we upconvert 6.95V to 10V.

PS thanks guys for sharing. Love your research, die shots, etc :)
 

Online Kleinstein

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Re: Ultra Precision Reference LTZ1000
« Reply #2432 on: November 08, 2018, 05:57:01 pm »
The error signal from the LTZ1000 is first amplified by the transistor inside the LTZ1000. This transistor has a voltage gain of around 200. The OPs only see the amplified error signal. So compare the effects at the transistor base the OPs offset and noise is effectively attenuated by that factor of 200.

So an 1 mV offset form the OP would result in some 5 µV extra voltage shift for the whole circuit.
The amplification be the transistor also adds to the loop gain. So even if the OP would have a gain of only 100K the total loop gain would be at some 20 millions and would thus only contribute some 0.3 µV to the 7 V output. So I don't think the amplifiers gain should be that important.

The main point's for the LT1013 are that it is well behaved on start up, e.g. with the supply still low, does not show phase reversal and has low enough current noise to work with some 70 K input resistance. Noise is well good enough.
 
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Offline VK5RC

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Re: Ultra Precision Reference LTZ1000
« Reply #2433 on: November 12, 2018, 09:17:18 am »
A photo of the 1st 3 DrFranks pcb  ltz10000A, with vishay s102 120ohm, TEs others, x3 tps7a4901 low noise psu . Having a little warm up.
Thanks DrFrank et al!

Later I will have some data about the effect of an 800km road trip on a 3458 (for calibration)
Whoah! Watch where that landed we might need it later.
 
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Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2434 on: November 12, 2018, 05:43:46 pm »
Be careful with the unbuffered reference output, prevent shorts by accident.

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Offline VK5RC

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Re: Ultra Precision Reference LTZ1000
« Reply #2435 on: November 12, 2018, 07:53:23 pm »
I have a procedure to reduce that risk, the ltz's hot is the last connected and the first disconnected.
Whoah! Watch where that landed we might need it later.
 

Offline TiN

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Re: Ultra Precision Reference LTZ1000
« Reply #2436 on: November 14, 2018, 05:00:53 am »
Perhaps interesting dataset for somebody curious about how freshly built LTZ ref behave when first powered on, and how initial days of settle look like.



Four meters used for sampling:
* 3458A with Keithley 7168 nV-scanner card (ch1-ch8)
* 3458A (drifty ADC) on black HPC chart.
* K2002 (K4 chart)
* second K2002 (K6 chart) measuring my 24/7 792X as main 10V reference (LTZ FX based)

No aircon, so bit higher ambient temps than usual 24c
From November 7 I restart logging, and ran ACAL DCV on 3458A drifty. You can see it's ADC drift on first 2 days as ~+2ppm a day.
But to my great surprise drift on ADC become <0.1ppm a day afterwards. I'm running multiple ACALs now every day. CAL72? value also show similar data.
I don't believe in self-fixing 3458 ADCs, but never know. Meter was left running for about a month, drifting.
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Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2437 on: November 15, 2018, 07:45:13 pm »
So, you have a jumper and two drifter out of 8 new build LTZ1000 references? Or did the other references had time before this measurement to burn in?

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Offline TiN

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Re: Ultra Precision Reference LTZ1000
« Reply #2438 on: November 16, 2018, 01:07:16 am »
Jumper is same LTZ1000A chip from eBay 3458 A9.
CH1(2) reference had few days runtime before. CH2-CH8 are all first power on (not counting few minutes long test runs). K2002-6 is my 24/7 10V FX reference (uninterrupted power since Feb'18).

I'll need to check CH6 and CH8 units though.

Here I rearrange data to use last yesterday value as 0ppm reference. It's bit easier to see settling time on difference channels.
« Last Edit: November 16, 2018, 01:08:49 am by TiN »
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Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2439 on: December 03, 2018, 06:07:05 pm »
One reference fully assembled and running on 3458A since 400h with 10V boost installed. Another 5 references only buffered are almost ready to go and 4 references are still waiting for their LTZ resistors to arrive. What about the other boards that have been spread over the whole world?

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Offline Sprock

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Re: Ultra Precision Reference LTZ1000
« Reply #2440 on: December 04, 2018, 09:21:52 am »
Hello all,
Resitors still in Frankfurt / Germany.
regards Sprock
 

Offline BradC

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Re: Ultra Precision Reference LTZ1000
« Reply #2441 on: December 04, 2018, 09:44:38 am »
What about the other boards that have been spread over the whole world?

Sitting in a big box with other lonely parts. Resistors have been sitting in a USPS facility in Sanfransico for a week now. They should get here before Christmas, just in time for the festive pause hopefully resulting in some assembly in the new year.
 

Offline pansku

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Re: Ultra Precision Reference LTZ1000
« Reply #2442 on: December 04, 2018, 10:04:18 am »
What about the other boards that have been spread over the whole world?

Waiting for parts and the ability to use my right hand for soldering *sigh*
 

Offline SvanGool

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Re: Ultra Precision Reference LTZ1000
« Reply #2443 on: December 04, 2018, 11:45:27 am »
@Sprock:

Nice card guides, may I ask where you got those?
I assume you are using a bigger enclosure than the Hammond 1455C1210, not (I like the direct ref option you still maintained)?
# Don't hurry, the past will wait. #
 

Offline Sprock

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Re: Ultra Precision Reference LTZ1000
« Reply #2444 on: December 04, 2018, 02:00:31 pm »
Hi
@ SvanGool,

guides are from scrapp box. The original is from Phönix Type FLP/SKBD.
Yes, you are right the case is bigger. It is the 1455 J 1210  instead of C.
No, all 3 boards will get different boxes. Only one in the black aluminium
with board guide.
regards
Sprock
 

Offline SvanGool

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Re: Ultra Precision Reference LTZ1000
« Reply #2445 on: December 04, 2018, 02:12:54 pm »
Thanks !

Mouser has them: https://www.mouser.de/ProductDetail/Phoenix-Contact/2204121 (but not on stock)
« Last Edit: December 04, 2018, 02:19:28 pm by SvanGool »
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Offline alex-sh

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Re: Ultra Precision Reference LTZ1000
« Reply #2446 on: December 05, 2018, 08:51:38 pm »
One reference fully assembled and running on 3458A since 400h with 10V boost installed. Another 5 references only buffered are almost ready to go and 4 references are still waiting for their LTZ resistors to arrive. What about the other boards that have been spread over the whole world?

-branadic-

Mine is still in the box waiting for resistors (group buy on eevblog).

Nice boxes you have. What are they and where did you get them? Are they on Digi-key?
 

Offline Haasje93

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Re: Ultra Precision Reference LTZ1000
« Reply #2447 on: December 05, 2018, 09:40:53 pm »
Hi!

On page 93 is your awnser. But i have here the link for the cases on Digikey.
https://www.digikey.com/products/en?keywords=1455C1201

Regards,
 
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Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2448 on: December 05, 2018, 09:59:54 pm »
Exactly, Hammond 1455C1201 is what the board is designed for. I had a colleague milling the frontpanels for me. The files for them are available a few posts above.

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Offline dkozel

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Re: Ultra Precision Reference LTZ1000
« Reply #2449 on: December 06, 2018, 11:39:14 pm »
I've ordered the long lead time items but have to finish selecting the last few more basic bits and get them ordered. I've been distracted with figuring out how I'm going to measure these once they're assembled. I don't want to miss the burn-in and do want to measure the three I'm building simultaneously.

I've started testing and warm-up of a pair of 3458A multimeters that I've borrowed (Thread). Along side that I've been looking at different scanner options and managed to find a nice deal here on the forum for a Keithley 7001 with 7011-S cards. They're spec'd for <500nV offset voltage, so >10x worse than TiN's 7168 cards, but I imagine >10x easier to get too. ;) I look forward to the day they aren't good enough for my needs.

Still need to get some cables together, but the last few pages of this thread as well as the various other low EMF threads have been useful there.

Branadic, quick question for you, do the LTZs have >4.2 mm of vertical clearance when in the Hammond case? I'm considering socketing the LTZs if it will work. Also, do you have any plans for how you're using the thermistor? I'm wondering if it's thermally a terrible idea to drill a small hole in the LTZ plastic covers (thanks for the models) and placing the thermistor in direct contact with the case. I have to imagine the thermal transfer would be minimal, but...  :-//

 


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