[volt-nuts] Eppley Standard Cell and What Is It?

[J. L. Trantham]

Well, it/they arrived today.  I will leave both my 'Standard Cells' sitting 
side by side and recheck later this week or next week and see what the 
measurements are.

In the mean time, I will have to see what I can measure from the 
'Thermopile' and find some boxes to pack up the 7081 for shipment.

Joe
----- Original Message ----- 
From: "J. Forster" <jfor at quikus.com>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Wednesday, September 21, 2011 9:34 PM
Subject: Re: [volt-nuts] Eppley Standard Cell and What Is It?


> If the Standard Cell has been shaken (in shipping) it needs to sit a long
> time before being useful as a standard. Some types of cells really do not
> like being inverted. It is designed to work into an open circuit....  ie:
> potentiometric comparison.
>
> The other item is abn Eppley Thermopile. The mpount is probably Spindler &
> Hoyer, and it fits Zeiss standard profile optical benches, made of
> aluminum or cast iron (most often).
>
> Inside the can, there is a metal disk that should be painted with a very,
> very flat black paint. The paint absorbs radiation from VUV to X-rays and
> turns the radiation into heat. The rear of the disk has a myriad of tiny
> thermocouples. The cold side goes to the case. The terminals are usually
> solid Cu.
>
> In use, it is usually read out w/ a nanovoltmeter. They are usually
> calibrated in mV/W. You will likely need a fairly strong light to see much
> voltage.
>
> Since it is a calorimeter, it can be used to compare the power in two
> optical lines of widely disparate wavelengths.
>
> Best,
>
> -John
>
> =============
>
>
>
>
>> I purchased an eBay item (190538109632) for the 'Standard Cell' that
>> included another item.
>>
>> What is it?
>>
>> The 'Standard Cell' is an 'Eppley Laboratory Catalog Number 100 (SN
>> 762058) Low Termperature Coefficient Standard of E. M. F.' that has
>> written on it '1.01931 @ 20 degree C' with a date of what I think is
>> '2-4-69' which I think means Feburary 4, 1969.
>>
>> Using my 'new' Solartron 7081, I read the voltage at 1.017844 +/- about 1
>> uV.  If I have the math correct, that is a decrease of about 35 uV/yr
>> which, I think, is about what is predicted for these cell's, assuming my
>> 7081 is accurate.
>>
>> I also have another Eppley Standard Cell (SN 821855) that reads 1.018709
>> but no date or prior reading on the unit.
>>
>> On another, unrelated note, I have been able to chase down the US branch
>> of Ametek in Oak Ridge, TN, and they will be getting my 7081 back to send
>> to England for calibration and 'service best effort', given that the 
>> meter
>> ceased production in 1998 with end of support 2008.  TAT is about 4 weeks
>> in England.
>>
>> Now, what is that other thing in the listing?
>>
>> Joe
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>
>
>
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