[volt-nuts] Solartron 7081 NVM FAIL

David C. Partridge david.partridge at perdrix.co.uk
Wed Apr 25 17:57:25 UTC 2012


Fabio,

Looking at the values from the CALIBRATE,DUMP command, I think you will find that all of them are default values which are loaded when the NVM isn't working at all.  

I think that the final message which reads "Refresh fail nvm page 1 & 2 are faulty" tells it all really.

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.

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).

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).

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" away!

What are your zeners like?

Dave
-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On Behalf Of Fabio Eboli
Sent: 25 April 2012 17:25
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Solartron 7081 NVM FAIL

Hello, have you tried with monitor mode?
service manual pages 8.3 and up, you should be able to get a raw value of constants from nvm, maybe also more error details.
Strangely the manual states to not try to recalibrate the zener and refer to solartron, while the 7061 manual just explains how to do, naturally the 7061 reference is simpler.

Fabio.

"David C. Partridge" <david.partridge at perdrix.co.uk> ha scritto:

> Bad news I think
>
> CALIBRATE,DUMP
> OK
> Vdc calibration constants
>  0.00000000E+00
>  167.776999E-03
>  0.00000000E+00
>  1.67776999E+00
>  0.00000000E+00
>  16.7776999E+00
>  0.00000000E+00
>  167.776999E+00
>  0.00000000E+00
>  1.67776999E+03
> Vac calibration constants
>  335.553999E-03
>  3.35553999E+00
>  33.5553999E+00
>  335.553999E+00
>  3.35553999E+03
> kOhm calibration constants
>  0.00000000E+00
>  167.776999E-03
>  0.00000000E+00
>  1.67776999E+00
>  0.00000000E+00
>  16.7776999E+00
>  0.00000000E+00
>  167.776999E+00
>  0.00000000E+00
>  1.67776999E+03
> Top Ohms range calibration constants
>  0.00000000E+00
>  12.0000000E+03
>  602.218329E-03
> Ratio terminals calibration constant
>  16.7776999E+00
> Zener current token value
> 255
> CALIBRATE,?
> E 7
> CALIBRATE ?
> OK
> Calibrate = Fail 1
> CALIBRATE,REFRESH
> OK
> Refresh fail        nvm page 1 & 2 are faulty
>
> D.
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com]
> On Behalf Of David C. Partridge
> Sent: 25 April 2012 14:50
> To: 'Discussion of precise voltage measurement'
> Subject: [volt-nuts] Solartron 7081 NVM FAIL
>
> The 74LS161 was the cuplrit, and the meter now starts up to display  
> the NVM FAIL message.   Substitution of the NVM from another meter  
> gave INITIALISED, so the problem is the ER-3400.
>
> I'm trying to work out whether the NVM FAIL message means just page 
> one of the calibration constants is gone and page two was OK, or 
> whether both pages are trashed?
>
> I can't remember - does the serial port use a "straight through"  
> connection - if so that would explain why it won't talk to me.
>
> If both pages are trashed, what hope to recalibrate the zener?
>
> Regards,
> David Partridge
>
>
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