Calibration of a 34401A is done electronically, however one needs to know the 
calibration security code.If unknown one needs to open the meter to enable 
calibration and then reassemble it and complete the calibration. The factory 
default calibration security code is HP034401 only 034401 need be entered from 
the front panel.Details are given in the service manual. Everything can be done 
from the front panel or over the HPIB.
A ~90ppm error shouldn't be a calibration issue as the initial calibration has 
to cope with the manufacturing tolerance for the LM399 internal reference.
For the 10V range the calibration source needs to be accurately known and 
within the [9, 11]Volt range.It also needs to be reversed to allow linearity 

    On Wednesday, 12 October 2016 9:54 PM, Dr. David Kirkby (Kirkby Microwave 
Ltd) <> wrote:

 I have a 'friend" (actually a person who I have never met, but is a pain in
the ***).

He sold a Agilent 34401A multimeter which the customer said is out of
specification and can not be adjusted.

Quickly scanning the measurent results,  the  meter is not showing results
with any huge errors  (say 1%), but which (if any) range it is out of
specification I don't know. Unlike the Keysight calibration certificates I
have seen, the measurement results doesn't show the upper and lower limits
for the specification of the meter,  so one can not tell from a quick
glance if the meter is out of specification. One would need to study the
detailed specification.

*IF* I understand correctly, (and the data is in Spanish which I don't
speak),  with an input of 9,99990 V, the meter reads 9,99899 which  the
data  indicates is an error of  -91 uV/V with an uncertainty of 7..7 uV/V.

The lab said the meter can not be adjusted.  I don't know if they mean

1) This lab has no ability to adjust the meter.


2) It is too far off to adjust.

Does anybody know if a 34401A can be adjusted by a competent 3rd party lab,
or are the details of how to adjust the meter not available outside of

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