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we have got a problem with our newest purchased Keithley 2016 THD with measuring audio values - the display shows version C01 / A02:
We use these 2016 THD with automatic tester via RS232 (settings are: 19.2 kBaud, Flow: XonXoff, TX Term: CRLF) for stimulation of audio inputs
and measuring the outcoming signals like level, S/N ratio and thd.
Now we observed that the measured results do not meet the specified ranges, for example: expected value 0.775V +/-20%, measured 1.54V or expected thd <1% (typ. 0.12%), measure 2.2%!
When we exchange against an older one with version B12 / A02, B15 / A02 or B17 / A02, everything works fine.
Is there any possibility to downgrade the 2016 THD with version C01 / A02?
Or otherwise - which changes has been realized with version C01 /A02 that could have any impacts on audio measuring?
I remember having heard of a similar case with an instrument coming for repair. The service technician found no error as far as I remember
but the general thinking was that possibly a 50 ohm termination resistance was not used.
For clarity it would be helpful if you could attach a file showing detailed cabling.
We used the following settings:
CALL DMM ":OUTP:FREQ 1000"
CALL DMM ":OUTP:IMP OHM50"
CALL DMM ":OUTP:AMPL 1"
CALL DMM ":OUTP:STAT ON"
and we connected a 50 Ohm resistor to the outputs for termination.
As a result, the 2016 THD with version B17 / A02 then showed an amplitude with 0.5 V level.
But the 2016 THD with version C01 / A02 then showed an amplitude with 1.0 V level.
We assume, there must have been performed a significant change in the audio generator section with introducing version C01 / A02.
Now we are a little bit confused - which DMM does work correct?
If the version C01 / A02 is the right one, could it be possible to upgrade the older ones?
I have tested a 2o16 firmware B15 with your code, rear BNC output connect to front input terminals and a 50 Ohm resisistor in parallel:
Shows 1 V in ACV function (2 V without the 50 Ohm resistor).
and what about firmware version C01 / A02 - have you had already tested such one with the same generator settings?
We are now in a difficult situation, because we cannot use our new DMM 2016 with our test applications and we don't have enough
DMM 2016 with older firmware versions to cover all our test benches - so this problem must be solved asap!
Your answer is highly appreciated!
seeing the history and the multiple attempts I would propose to send in two of your units (one BXX, one C01 firmware)
showing different results at your site for EVALUATION to our local service department.
Having both units and your exact description at hand we should certainly be able to clarify the issue.
[Please use the word 'evaluation' when sending the units or asking for an RMA number.]
should we send the units to your service department in Germering, Germany?
If so, I will arrange everything after my return from vacation.
Thanks in advance
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