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

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Mar 15 07:19:03 UTC 2009

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 
> 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
make some of the instruments and standards they used to sell.
They also claim to have taken over from Leeds and Northrup.

Also see:

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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