USA Cal Club: Round 2

[zhtoor]

Precision Resistor Standard with many combinations:
I think I have this worked out. It will take 20 identical resistors in series, at the junction of each pair- a center-off DPDT toggle switch, use both contacts in parallel. 21 switches total. (Clip leads can substitute for actual switches)

Two buss bars, 2 binding posts.
Each junction can be neutral/Buss1/Buss2.

Any number of resistors in series could be placed in parallel with any other number of resistors in series.

The range would be from R/20 to 20R.
It's up to the math whizs to calculate the programming chart.

I'll call it the Diddle Box.

George Dowell

have a look at this:-

https://www.eevblog.com/forum/metrology/poor-man_s-resistive-ring-10k-standard/msg1447922/#msg1447922

and especially this:-

https://www.eevblog.com/forum/metrology/poor-man_s-resistive-ring-10k-standard/msg1456821/#msg1456821

best regards.

-zia

[GEOelectronics]

Thanks Zia


George Dowell

[TWMIV]

I would love to participate in this as I have two 4356a's that differ 4 counts from each other.

I have a gpib interface, temp sensors, and I believe everything else needed to measure and trend the data.

I am going to be doing an internship until the beginning of August, so I wouldn't be able to participate until then.

I may also be able to check it against a calibrated meter in one of my school's labs, but I wouldnt be able to get more than a few hours of data from it.

Sent from my Moto G (4) using Tapatalk

[Dr. Frank]

AFAIK, calibration lab techs don't get the summer off due to lack of business. It's also doubtful that sales and shipments of precision meters cease during mid winter and mid summer. The storage temperature range for the LTZ1000 is -65 to 150 C, so I doubt you could damage one. Didn't see a spec for metal foil resistors, but I'd be surprised if it was an issue. The big question is hysterisis of everything as you cycle the temperature and the only way to find out is to try it. Temperature and vibration in shipping is one reason I dislike trimpots. Too many change by tapping them, so they're certainly subject to changes during shipping.

Well no, that's not a question of damage, but of hysteresis of the chip, in the completed circuit.
Have a look into the specifications of the Datron 4910 and 7001, both are limited in their storage temperatures.
The 4910 from -40 to +50°C (Great!), but the 7001 has limits of -18..+45°C for transit, and 0 ..45°C for storage, plus the clear hint inside the manual, that excessive (low) temperatures will cause hysteresis, being removed by the unique conditioning procedure.

Early this year, I also shipped two LTZ1000 modules during cold weather to friendly volt-nuts, several degrees below zero °C, and both references showed a persistent shift of output, several ppms, although they showed absolutely no hysteresis during their characterization, between +15° and +40°C, at 50°C oven temperature.

Therefore, the selection of seasonal shipment is very important, as is the star-wise shipment, to get a baseline, back at the initial lab.

Although both of my references had shifted, I could to some limits decide from these drift data, which voltage value of the returned sample was to be expected... So I concluded in the end, that my Volt agreed to acberns calibrated Volt within parts of one ppm.

Frank

[cellularmitosis]

Interesting, I'm guessing the Pickering-patent anti-hysteresis conditioning in the 7001 only applies to the LTZ chip itself (by manipulating the heater set-point), and no equivalent anti-hysteresis conditioning is performed to the precision resistors?

Dr. Frank, were you able to attribute different levels of hysteresis to the 7V vs 10V output of your ref?

[Dr. Frank]

Interesting, I'm guessing the Pickering-patent anti-hysteresis conditioning in the 7001 only applies to the LTZ chip itself (by manipulating the heater set-point), and no equivalent anti-hysteresis conditioning is performed to the precision resistors?

Dr. Frank, were you able to attribute different levels of hysteresis to the 7V vs 10V output of your ref?

Correctly, that's the scope of the patent. Still, I doubt that that procedure was effectively working inside the 7001, as in another document, Pickering mentions a low oven temperature of maybe 45°C only, which would prohibit a symmetrical +/- 40°C temperature swing.
I'm looking forward to TiNs reverse engineering..

I did only monitor the 7.15V output.

But I also encountered the well known hysteresis on the 10k VHP202Z resistor reference, which was also in these packages..
'Well known' means, that Vishay re-measured two of them at -40 and +175°C, and sent them back with a hefty persistent shift.. which also could be removed by thermal cycling.
The direction of the shift correlated in both cases with the direction of the temperature excursion.

So the specific resistors for the 7/10V amplifier in your circuit should also be characterized for a broader temperature range.

[rhb]

For a reference which travels by common carrier, it seems to me that several features are desirable:

the ability to thermally cycle the entire reference by means of a Peltier device through an annealing cycle as well as maintain a measurement temp independent of ambient.

temperature logging during transit and use

phase change media container with 5-10 C and 35-40 C melting points if we can find affordable media

lots of insulation in the shipping container (e.g. 6+" of styrofoam)

I can't see any reason that a reference can't travel and provide results close to the limits set by 1/f noise with good lab technique.  Not likely to be easy to achieve, but physics is not random.  It just gets to set the rules to suit itself.

[hwj-d]

Ok.

Now that we know in detail what would be most desirable, along with all the negative circumstances that might cause the project to fail for transport reasons, let's start with what would be practically feasible.

The task:
to transport a 50mm x 55mm x 25mm metal box and accessories over a period of about 1 week as temperature-neutral as possible.

That shouldn't be an insoluble task, also for pedantic Voltnuts! 

And please, we are not dealing with requirements as they are placed on a 732a/b, nor is the operation of a peltir element in a "in itself contained" transport box not particularly, excuse me, "intelligent". 

How about, for example, a matching, slightly more solid but as small as possible styrofoam box, as used in the medical and biological fields?

[zhtoor]

For a reference which travels by common carrier, it seems to me that several features are desirable:

the ability to thermally cycle the entire reference by means of a Peltier device through an annealing cycle as well as maintain a measurement temp independent of ambient.

temperature logging during transit and use

phase change media container with 5-10 C and 35-40 C melting points if we can find affordable media

lots of insulation in the shipping container (e.g. 6+" of styrofoam)

I can't see any reason that a reference can't travel and provide results close to the limits set by 1/f noise with good lab technique.  Not likely to be easy to achieve, but physics is not random.  It just gets to set the rules to suit itself.

hello,

use these:-

http://www.tempil.com/temperature-indicators/temperature-indicating-sticks/tempilstik/

best regards.

-zia

[rhb]

The point of the Peltier devices is not to maintain a constant temperature during transport.  It is to provide facilities for annealing if it is required.  As they appear to be low cost, it seems to me sensible.  I'll know more when the 10 I ordered arrive.  I can't see any justification for shipping hot.  I think there are less difficult solutions.

Using Peltier devices for annealing appears easy and cheap.  Finding phase change materials is a lot harder.  That's in the "would be nice' category.

I can see no reason not to attempt  to develop shipping procedures suitable for a 732a/b.  As a scientist, I have been quite underwhelmed by what I've read on the subject.  It is perhaps merely poor writing, but I have not been impressed by what I have read so far.

What I have suggested are the same procedures as used for shipping food or medical materials.  I have an acquaintance who represents a company which makes temperature controlled shipping containers for medical use.  Subjecting a voltage reference to dry ice in a styrofoam chest as done with steaks is not a good idea if you want the voltage at the receiving end to be the same as the voltage at the shipping end.

There are three requirements:

Maintain as consistent a temperature in transit as possible

Track what the transit temperatures are

Have a means of annealing the device if required

I happen to think that the "amateurs" n this group are capable of doing first rate professional level science with a modest amount of cooperation.  In my view the biggest obstacle is people who "fail to recognize their limitations"  to paraphrase  Harry Callahan in "Magnum Force".

[hwj-d]

I happen to think that the "amateurs" n this group are capable of doing first rate professional level science with a modest amount of cooperation.  In my view the biggest obstacle is people who "fail to recognize their limitations"  to paraphrase  Harry Callahan in "Magnum Force".

This is a nice attempt to shift a technical problem to the side of an "ad hominem". I do not like such categorizations because they don't contribute to the solution. It is sufficient if we try to solve the technical priority, please.

[FriedLogic]

I can't see any reason that a reference can't travel and provide results close to the limits set by 1/f noise with good lab technique.  Not likely to be easy to achieve, but physics is not random.  It just gets to set the rules to suit itself.

Hi,

Unfortunately, there can still be serious limits to how practically predictable it is - think weather, earthquakes, etc.
Just because semiconductors are small does not mean that they're simple. I can't remember the details now, but there was a paper a while back comparing microfractures in a crystal with faults in the earth's crust.

[TiN]

  USA Cal club reference ready to do some initial checking now.

[cellularmitosis]

 

[hwj-d]

What a beauty ... 

[bitseeker]

USA Cal club reference ready to do some initial checking now.

Wow! That looks really fancy to my volt-noob eyes. Looking forward to working with it.

[Svgeesus]

I would be very happy to participate in this round, if that is okay. My meter is not up in volt-nut territory, it is a 6.5 digit Keysight 34465A so this LTZ would be considerably better than the LM399 in the meter. On the other hand, the meter is a recent purchase (purchased new, four months old) and it was purchased with both calibration and uncertainties.

[GEOelectronics]

I would be very happy to participate in this round, if that is okay. My meter is not up in volt-nut territory, it is a 6.5 digit Keysight 34465A so this LTZ would be considerably better than the LM399 in the meter. On the other hand, the meter is a recent purchase (purchased new, four months old) and it was purchased with both calibration and uncertainties.

PS I live in Missouri.

George Dowell

[cellularmitosis]

I would be very happy to participate in this round, if that is okay. My meter is not up in volt-nut territory, it is a 6.5 digit Keysight 34465A so this LTZ would be considerably better than the LM399 in the meter. On the other hand, the meter is a recent purchase (purchased new, four months old) and it was purchased with both calibration and uncertainties.

That sounds great!

----

I threw together this little guy this evening, to include with the ref.  It also spits out CSV data over the USB (serial) connection (for datalogging).

Now I just need to print up a shipping label and get this train a movin!

[TiN]

Initial tempco looks alright. Good enough not to spoil linear response with compensation resistor voodoo. My output 10V stage on previous boards also have opposite tempco so overall we might break even. 



I'd like to make note that this reference needs bipolar 12V supply!

[orin]

I threw together this little guy this evening, to include with the ref.  It also spits out CSV data over the USB (serial) connection (for datalogging).

Nice.  We can be on the same page as far as temperature is concerned.  I know my Control Company NIST traceable thermometers are out of cal.

So I dropped off the Fluke 8845A for calibration with data at Fluke Command Central in Everett this morning.  It was quite entertaining wading through the quagmire of their web site to get the RMA... No, it's not broken, I just want a calibration.  The signs on the Fluke Service Center building are no better... SW corner of the building... OK... Locked door with threatening signs about requiring escort beyond this point, but how to get their attention?

With a little luck it will be back and still be in cal when it's my turn   It's the 34461A's turn next year.

[bitseeker]

I'd like to make note that this reference needs bipolar 12V supply!

TiN, what kind of stability does the supply need to have to power it?

[TiN]

Decent quality linear bench PSU will be fine. For critical measurements (e.g. noise) I use two VRLA 12V batteries.

[kj7e]

12v Bipolar power supply... Check!


On another but related note, I'm putting together a post detailing the recent journey my KX based LTZ1000 based 10v reference made to ENI Labs (thanks CalMachine!), where it was compared to their house master references as well as CalMachine's home references over the last few weeks.  The reference was shipped powered on both directions.  Here is a very brief summery, more details coming in its own thread.

As measured by my Keithley DMM7510 prior shipping;
10.000000

As measured at ENI Labs;
9.9999637 -  3458 option 002, cal'ed at Fluke Std Labs 5 moths ago

Dif;
0.0000363 (3.6 ppm low)

Ryan adjusted the buffer trim upward by 37.7uV to the reference now measured;
10.0000014 (0.14ppm high)

I should now “theoretically” measure;
10.000038

My real measurement now is;
10.000039

I love it when the math checks out.

Also, this was adjusted per his home Fluke 732B, which was last known to measure 10.0000007 or 0.07ppm high compared the ENI Labs master 732B (which was away at Fluke Park Standards lab the last few weeks).   Ryan is going to verify his 732B against the Shops 732B again to re-verify this number.  So I'm confident I now have a very, very good realization of 10v to compare from.   

[zhtoor]

Decent quality linear bench PSU will be fine. For critical measurements (e.g. noise) I use two VRLA 12V batteries.

how about going the battery route as the standard power supply protocol.
it is cheap enough and readily available.
and keeps the mains-line-daemons away

best regards.

-zia