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According to the manual, there are only two 'adjustments' that can be made
on a 3457A, Input Offset Amplifier adjustment and AC Converter Frequency
Response, both needed only if there is a 'HARDWARE ERR' failure message
after 'TEST' is selected and then only if it is a specific 'AUXERR' or 16 or
256 is seen. Otherwise, all the calibrations are done from the front panel
with specific inputs from the front panel.



The CALNUM? is incremented by 'several digits' with a 'complete
calibration', one for each calibration point entered, per the manual.
Interestingly, when I sent my two 3458A's to Agilent for calibration, the
CALNUM incremented by only 1. However, when I calibrated one of them before
sending it to Agilent, (since I lost the data in the DALLAS CALRAM chip that
I was removing) the CALNUM went from 1 to something like 34 or something. I
don't recall. It seems that if you have the appropriate software to run the
complete calibration protocol, it only increments by '1' instead of by all
the data points entered. Such software exists for the 3457A but I have
never seen it available 'on theBay'. I suspect Agilent would have that
software and equipment to do that calibration and, thus, an Agilent
calibration may only increment the CALNUM? by 1.



When getting an Agilent calibration of the 3458A, you get 'As Received' and
'As Completed' data. Very helpful to me in that the only two points my
'House CAL' of the one 3458A failed were the two 'midrange' AC Voltage
values. All else 'PASSED'.



I agree with Dave. If it's HP/Agilent, I prefer Agilent to do the CAL. If
it's Solartron, I prefer AMETEK (Solartron), etc.



I believe that having some 'basic' professionally calibrated instruments
(DMM's, Noise Sources, Power Sensors, Frequency Standards (unless you have a
GPSDO, CS Standard, etc.) etc.), that you can then use as 'transfer
standards' to do your own 'in house' calibration of other instruments, is
very important if you want to set up a reliable workshop.



Of course, you will also need a 'stable' source of the various signals that
you will use to be 'measured' by the various 'DUT's', such as resistance,
voltage, current, frequency, etc. The 3458A is relatively easy to
calibrate, requiring only 10.000000 VDC, 10000.000 ohms, and some AC voltage
at various frequencies, IIRC. I have never CAL'd a 3457A but the 3478A is a
multi-step process.



This whole thing can become very 'addictive'. Be careful.



Joe