Tektronix Technical Forums are maintained by community involvement. Feel free to post questions or respond to questions by other members. Should you require a time-sensitive answer, please contact your local Tektronix support center here.

Keithley 2016 THD - audio values too high

2015, 2015-P, 2016, 2016-P
Post Reply
NorbertBredow
Posts: 4
Joined: September 9th, 2014, 12:23 am
Country: Germany

Keithley 2016 THD - audio values too high

Post by NorbertBredow » September 9th, 2014, 1:30 am

Hello,

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?

Best regards
Norbert Bredow

Norbert W
Keithley Applications
Keithley Applications
Posts: 227
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by Norbert W » September 9th, 2014, 1:57 am

Hello,
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.

NorbertBredow
Posts: 4
Joined: September 9th, 2014, 12:23 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by NorbertBredow » September 9th, 2014, 10:46 pm

Yesterday we did a deeper investigation and compared a Keithley 2016 THD with version B17 / A02 with another 2016 THD with version C01 /A02.
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?

Best regards
Norbert Bredow

Norbert W
Keithley Applications
Keithley Applications
Posts: 227
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by Norbert W » September 10th, 2014, 5:32 am

Hello,
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).

NorbertBredow
Posts: 4
Joined: September 9th, 2014, 12:23 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by NorbertBredow » September 10th, 2014, 9:08 pm

Hello,

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!

Best regards
Norbert Bredow

Norbert W
Keithley Applications
Keithley Applications
Posts: 227
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by Norbert W » September 11th, 2014, 8:00 am

Hello,
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.]

NorbertBredow
Posts: 4
Joined: September 9th, 2014, 12:23 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by NorbertBredow » September 11th, 2014, 9:19 pm

Okay,
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

Best regards,

Norbert Bredow

Norbert W
Keithley Applications
Keithley Applications
Posts: 227
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: Keithley 2016 THD - audio values too high

Post by Norbert W » September 15th, 2014, 2:50 am

Hello,
yes, this is the right place for your shipment.
Have a fine vacation time.

Post Reply

Return to “Series 2015 & 2016 THD/Audio Analyzers”

Who is online

Users browsing this forum: No registered users and 4 guests