[volt-nuts] Solartron 7081 NVM FAIL
David C. Partridge
david.partridge at perdrix.co.uk
Thu Apr 26 10:11:48 UTC 2012
Here are links to some photos of the two different references in the 7081s
>From serial number 180 (my working one):
I can't identify what this zener actually is ...
and from serial number 301 (the one with the dead NVM):
This one is a 1N829
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On Behalf Of Fabio Eboli
Sent: 25 April 2012 20:02
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Solartron 7081 NVM FAIL
> I will try looking in monitor mode tomorrow, but suspect that I will
> see binary zero or FF depending on HOW the EAROM has failed.
Yes, probably you are right.
> Do you have a scanner, it might be interesting to see how they propose
> doing the zener calibration for the 7061? I guess you need an
> environmental chamber, an accurate controllable current source and a
> logging voltmeter (at least I can provide one of the three, as my
> other 7081 still works OK).
I had scans already done.
The instructions are very crude:
Here the schematic of the reference:
I imagine that the second order temperature compensation can be problematic in the process, maybe this is why they don't provide instructions to recalibrate the zener.
> The quote from Ametek for a FULL calibration including zener is rather
> eye watering, and I doubt they would do a zener only calibration (or
> if they would it would be equally expensive).
Just a question, you can also answer privately, but what is the usual price on the used market for a 7081, good or broken?
I've only seen one on ebay (other than the ones at >1k euro that never sell), and I've never seen one here on the surplus resellers.
> A question for the other 7081 owners: The zener diodes in this 7081
> and a 7071 are 1N829 in an orange glass DO7 (I think) case. The
> zener in my original 7081 is quite different as it is in a
> hermetically sealed metal can that looks for all the world like it
> should hold a crystal. What is more, it is thermally connected to the
> AD590 temperature sensor while the other two the diode is about 3/8"
> What are your zeners like?
That's interesting! Have you some photo? :)
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