[time-nuts] OT: Basics of voltage calibration?

[Bruce Griffiths]

Brian Kirby wrote:
> search LTZ1000, LM399, and LH0070  at www.linear.com , also get app 
> notes AN42, AN82, and AN86   -   and by the way, most big parts houses 
> have quit carrying these references  -  but they can be ordered direct 
> from Linear Technology. 
>
> The LTZ1000 is used in HP3458A multimeters and a lot of voltage 
> calibrators from Datron, Fluke, etc.  The LM299 and LM399 were used in 
> HP 3457A and HP3456A, and others.
>
> more info on LM199/LM399 at national semiconductor, and a few app notes, 
> AN 161 , AN184,
>
> finding a good standard cell, is hard to do nowadays.  I bought 6 units 
> on ebay, 2 were from folks that had them and they were able to test and 
> furnish  data, and the other four were old and the voltage was too low 
> to be stable.  Basically if the voltage is not 1.0183 volts and above 
> they are no good.  They are finicky and I would read up on them before I 
> would purchase one.  NIST had a paper on them that explained the history 
> of them, their construction, and how to handle them and the temperature 
> conversion formulas for the saturated cells.  Check out NIST 250-28 
> Solid State DC Voltage Calibrations,  A Sub-PPM Automated 1-10 Volt DC 
> Measuring System by Bruce E. Field,  NBS Measurement Services:  Standard 
> Cell Calibrations, also by Bruce E. Field,  Standard Cells - Their 
> Construction, Maintenance and Characteristics by Walter J. Hamer all at 
> NIST.
>
> Look up Kelvin Varley dividers - I don't know if these folks are still 
> in business Julie Labs and ESI.  Leeds and Northrup made a few also.
>
>   
One of the best ways to ensure you get a good Weston standard cell is to
make your own.
However obtaining the Mercury and the Cadmium sulphate may be difficult.
The mercury salts are easily produce by electrolysis in a dark enclosure
(they are photosensitive).

Julie research labs are long gone, however
http://www.ohm-labs.com/
make some of the instruments and standards they used to sell.
They also claim to have taken over from Leeds and Northrup.

Also see:
http://www.ietlabs.com/

Fluke still make the 720A KVD.


> HP had some app notes on measurements, look up the 3456A, 3457A, 3458A 
> and it should show some app notes for them.
>
> Zicor had AN177, I believe Intersil bought them
>
> And Keithley had a free book called Low Level Measurements Handbook - 
> Precision DC Current, Voltage, and Resistance Measurements thats worth a 
> read.
>
> If you can find a copy of Current Sources and Voltage References: A 
> Design Reference for Electronics Engineers, by  Linden Harrison, its a 
> good read on a lot of semiconductor references in the last 15 years or 
> so - I would see if you can find it in a library somewhere, if you 
> purchase it its about $50-75 on the used market.
>
> Brian - KD4FM
>
> John Ackermann N8UR wrote:
>   
>> I'm interested in learning some basics about precision voltage 
>> calibration (as can be realized by the hobbyist, not Josephson Junction 
>> systems!).  A Google search hasn't turned up anything like a tutorial.
>>
>> Anyone know of any good app notes or other references on things like 
>> standard cells, zener references, precision potentiometers, etc? -- and 
>> how to use them?
>>
>> Thanks,
>>
>> John
>>
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>   

Bruce