Author Topic: USA Cal Club: Round 2  (Read 23544 times)

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Online Echo88

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Re: USA Cal Club: Round 2
« Reply #250 on: May 14, 2019, 08:27:14 pm »
Id like to participate in the EUCalClub as well.  :)
 

Online hwj-d

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Re: USA Cal Club: Round 2
« Reply #251 on: May 14, 2019, 08:44:50 pm »
It would be a good topic for stuttgart to organize an eu-calclub.
 

Online mimmus78

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Re: USA Cal Club: Round 2
« Reply #252 on: May 14, 2019, 10:58:04 pm »
EUCalClub consider me in
 

Online hwj-d

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Offline vindoline

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Re: USA Cal Club: Round 2
« Reply #254 on: May 15, 2019, 01:25:45 am »
As HJW-d announced, the USA CalClub reference has arrived back in the USA! The package arrived yesterday and I haven't had time to do anything but power it up. It's looking good so far and I'll monitor it for 24 hrs or so. I'm still expecting the other new reference from TiN. My current thinking is to wait for both references so we can send them around together. I expect most people would like to be able to use and compare the two. 
 
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Offline bitseeker

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Re: USA Cal Club: Round 2
« Reply #255 on: May 15, 2019, 03:04:46 am »
Ok, now it's time to lift the veil, what I did with the lid.

Now there are two precise resistors 1k and 10k under it, with the ability to take a real 4-wire measurement, but without changing the dimensions of the tekko housing. I put little but precise 4-wire measurement cabels in the package, hoping that was a good and usefull idea. Some pictures:

(edit translation)

I like it! :-+

It's also exciting to see interest spring up for an EU Cal Club. Thanks, HW!
Life is better under the TEA. ♪♩♫ Under the TEA. ♩♫
 
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Offline bitseeker

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Re: USA Cal Club: Round 2
« Reply #256 on: May 16, 2019, 01:39:16 am »
Some info from Dr. Frank regarding LTZ references (from the new EU Cal Club thread):

Hello,
we may discuss the stability problems in depth on the Metrology Meeting.
I've had bilateral exchanges of LTZ references and resistors already with a number of volt-nuts.

I usually have sent one LTZ1000, un-powered, and one VHP202Z, 10k, with built-in temperature sensor, allowing precise resistance calculation over temperature.

That fits in a small DHL packet at low cost.

Transfer is not possible during winter, as the LTZ especially at temperatures < 0°C shows hysteresis of several + ppm, but during spring .. harvest, it will retrace its nominal value within < 0.5ppm.

Round trip measurements are necessary to confirm successful transfers, as well as systematic data evaluation.
Life is better under the TEA. ♪♩♫ Under the TEA. ♩♫
 

Offline CatalinaWOW

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Re: USA Cal Club: Round 2
« Reply #257 on: May 16, 2019, 08:44:09 am »
I would think this would threaten transfer year round as most shipping methods have an air transport leg, and the cargo hold can easily reach this temperature.
 

Offline nikonoid

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Re: USA Cal Club: Round 2
« Reply #258 on: May 16, 2019, 09:20:44 am »
Shipping powered reference is more expensive as it adds weight, size and requires quicker shipments.

What about doing hysteresis recovery procedure after shipping, like in Pickering patent? It has expired, I believe, so free to be used.

This way we can ship references unpowered year round.
 

Online hwj-d

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Re: USA Cal Club: Round 2
« Reply #259 on: May 16, 2019, 10:16:32 am »
CatalinaWOW

You'd think. In reality we now have a LTZ1000 Ref, which has already been transported twice across the "big pond". Now it depends on the extent to which the measured values actually differ. Certainly also the demand of accuracy plays a role.

 ;)
 

Offline Dr. Frank

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Re: USA Cal Club: Round 2
« Reply #260 on: May 16, 2019, 04:24:12 pm »
Shipping powered reference is more expensive as it adds weight, size and requires quicker shipments.

What about doing hysteresis recovery procedure after shipping, like in Pickering patent? It has expired, I believe, so free to be used.

This way we can ship references un-powered year round.

Yes, the LTZ 1000 can be recovered by cycling the temperature, following the Pickering Patent. For personal use, this method has always been 'free'.

I assume, that this method did never work properly in the Datron 7000 application, as its oven temperature is described as being 45°C, and symmetric temperature sweeps of +/- 40°C, as described in this patent US 5369245 then would never be achievable at usual room temperatures.

The LTZ 1000 shows an asymmetric hysteresis behavior, though.
The hysteresis at low temperatures is bigger, than at higher temperatures. This is also indicated inside a paper about the Datron 7000.

Therefore, such a technique has to be run kind of asymmetrically, and the correct procedure (contrasting the original patent) has to be evaluated.

Otherwise, a temperature logger could be added to the packet, and a mandatory round-trip-measurement might detect hysteric shifts, that is to consequently measure the voltage before and after the travel at the same laboratory.

Frank 

PS: demonstration of this problem, with Pickering document:
http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1882325/#msg1882325
« Last Edit: May 16, 2019, 04:46:48 pm by Dr. Frank »
 

Offline TiN

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Re: USA Cal Club: Round 2
« Reply #261 on: May 20, 2019, 02:37:25 pm »
I'm sorry about all the delays, reference module for US Cal Club is shipped today.
Initial calibration data and measured stats:



My lab will get new SI Volt (doing JJA cal for my refs soon), so I will be able to confirm/deny the absolute uncertainty of my setup. Two 3458A and K2002 were used to perform all measurements.



Output provided by two Pomona 3770 low thermal EMF posts. Input power and auxilary circuitry using circular shielded connector (fanout cable included in package).

Power requirements : +11 to +15VDC, -2 to -15VDC, current limited at least 80mA. Power input is protected by 125mA fuse and TVS.
Optional PCB temperature sensor : MAX6610 (U4 on PCB), with isolated power +5V.
Optional ROM data storage: I2C EEPROM with isolated +3.3V power (ground shared with temp sensor).
Calibration data provided for temperature range +20 °C to +50 °C



Chip is LTZ1000A, setpoint 12.5/1K TCC VHP200 divider. Onboard regulator for LTZ1000A section is LT3042. Schematics is otherwise same as Linear's datasheet.



Output amplifier is Analog ADA4522-2 chopper, together with bipolar transistor driver. Reference can survive short at the output for indefinite time.
FX module output driver can sink or source up to 20mA, but here module cannot maintain output accuracy because kelvin sense lines are not routed to the binding posts.

Inline fuses are hidden in yellow tube. Suggest not to break them :)
Just realized, somebody melted few film cap casing  :palm:



Looking forward to see results on this by US members. I would recommend not to open the box to avoid magic ppms leaking out  :popcorn:
« Last Edit: May 20, 2019, 02:39:55 pm by TiN »
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Offline bitseeker

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Re: USA Cal Club: Round 2
« Reply #262 on: May 20, 2019, 03:16:49 pm »
Exciting! Definitely worth the wait. Thank you, TiN! I promise not to let any ppms escape. ;D
Life is better under the TEA. ♪♩♫ Under the TEA. ♩♫
 

Online hwj-d

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Re: USA Cal Club: Round 2
« Reply #263 on: May 20, 2019, 04:11:32 pm »
 :clap:

Ok, I'll sign in again...  ;D   ;)
 

Online hwj-d

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Re: USA Cal Club: Round 2
« Reply #264 on: May 20, 2019, 04:22:36 pm »
To provide it against high import customs, declare it as 10$ selfmade electronics scrap ...

:-DD     ;D   :-+

(edit: excuse my joke TiN, the reference is overwhelmingly well done)
« Last Edit: May 20, 2019, 05:00:30 pm by hwj-d »
 

Offline vindoline

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Re: USA Cal Club: Round 2
« Reply #265 on: May 21, 2019, 09:23:46 am »
reference module for US Cal Club is shipped today. . . .
Looking forward to see results on this by US members. I would recommend not to open the box to avoid magic ppms leaking out  :popcorn:

Wow! Just, wow. This is going to be exciting! A huge 'thank you' TiN!
 

Online JBeale

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Re: USA Cal Club: Round 2
« Reply #266 on: Today at 01:25:00 am »
Just read through the xdevs.com/article/792x/ page about that reference board; what a project!  Impressively photographed as well. I'm curious how the PCB is held mechanically inside the metal case, assuming it does not simply float. Is there some compression gasket around the edge?
 


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