[volt-nuts] Datron 1281

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Actually it's a 3.6V (SL-750/T) one. It still has ~3.68V, and no NVRAM 
checksum errors are reported.

It's a no opts unit (only DCV), so the errors are not related to 
resistance measurement.
As Hubert (Dankeschön) pointed out, it's related to the int cal src 
drifting outside certain ranges.
As Laurence (thank you) observed, it probably would be fixed with the 
int src cal characterization after ext cal, if nothing is physically wrong.

The manual specifies:
N.B.
Full Selftest cannot be selected unless a successful
'Internal Source Calibration' has been carried out
since the most-recent External Calibration.
Caution
The success of Full Selftest can be inhibited by:
• temperature not in the range: 13°C to 33°C;
• more than 1 year since Internal Source
Calibration executed;
• temperature more than 10degC different from
Internal Source Calibration; or
• presence of excessive RFI or Line noise.

2273	1V Range - Attenuated +10V Ref Magnitude Drift
	Digital comparison of the present magnitude against that
	recorded at the most-recent Internal Source Cal.
	+100mV Signal Mag. Drift   1-10ppm < drift < 1+10ppm

2283	100mV Range - Attenuated +10V Ref Magnitude Drift
	Digital comparison of the present magnitude against that
	recorded at the most-recent Internal Source Cal.
	+100mV Signal Mag. Drift   1-20ppm < drift < 1+20ppm


How would that drift be determined, without an ext cal?

Regards,
Gabi

On 1/20/2015 5:42 PM, Todd Micallef wrote:
> I have not seen inside a 1281, but my 4920 has a 3V battery for the cal
> constants. I am guessing that the unit would have flagged error codes
> 2110-2113.
>
> Looking at the specs, it looks like the meter uses the 1V and 100mV ranges
> for measuring resistance based on the selected range and whether or not it
> is in LoI mode. The error messages appear that it is a gross measurement
> error of over 100mV on both flagged ranges. I would think the 5522A would
> be good enough for a quick sanity check of all possible inputs.
>
> Todd
>