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

[Artekmedia]

Chuck

What exactly would be the extended characteristics on "old" cell that 
render it no longer useful?

Dave
NR1Dx


On 9/22/2011 8:32 AM, Chuck Harris wrote:
> As I understand it, an unsaturated cell that measures 1.0178V is many,
> many years
> past being useful as a standard, as is any unsaturated cell that
> measures below
> 1.0183V.
>
> Saturated cells are very rare outside of laboratory conditions, as
> inverting the cell
> will ruin it.  Unsaturated cells can withstand the topsy turvy travel
> conditions
> presented by shipping.
>
> -Chuck Harris
>
> J. L. Trantham wrote:
>> Roy,
>>
>> The 'experts' are here on the list. From my reading, they have about
>> a 50 uV/Yr
>> expected decline in value, thus the need for periodic 'calibration'.
>> I do not have a
>> feel for useful life expectancy but the two I have are in good
>> condition and only the
>> latest one has a value on the front of '1.01931 @ 20 degrees C' with
>> a date on the
>> side of '2-4-69'. This AM, it measures 1.017894. However, the 7081 is
>> not known to be
>> accurate, yet.
>>
>> The other cell still measures 1.018709 this AM.
>>
>> So, it would appear that they will make a good standard but will need
>> to be measured
>> from time to time to generate a log of date, temperature, and value.
>>
>> I wonder how long it has to be 'still' before it is again stable?
>>
>> Joe
>>
>>
>> ----- Original Message ----- From: "Roy Phillips"
>> <phill.r1 at btinternet.com>
>> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
>> Sent: Thursday, September 22, 2011 5:16 AM
>> Subject: Re: [volt-nuts] Eppley Standard Cell and What Is It?
>>
>>
>>> Joe
>>> Interesting point regarding the "Standard Cell", I have one that was
>>> purchased some
>>> 12 years ago made by Western. It must be well beyond its calibrated
>>> accuracy. It
>>> currently reads 1.018679 volts according to my 3458A. It seems to be
>>> stable but
>>> below its original labeled standard (label lost). Are they worth
>>> keeping ?
>>> Roy
>>>
>>>
>>> --------------------------------------------------
>>> From: "J. L. Trantham" <jltran at att.net>
>>> Sent: Thursday, September 22, 2011 2:37 AM
>>> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
>>> Subject: [volt-nuts] Eppley Standard Cell and What Is It?
>>>
>>>> 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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>>
>>
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>
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Dave&  Lynn Henderson
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