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Interfered output at 2634B

Models 2601, 2602, 2611, 2612, 2635, 2636
Models 2601A, 2602A, 2611A, 2612A, 2635A, 2636A
Models 2601B, 2602B, 2604B, 2611B, 2612B, 2614B, 2634B, 2635B, 2636B
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Posts: 3
Joined: November 25th, 2013, 6:48 am
Country: Germany

Interfered output at 2634B

Post by rododendron » July 29th, 2014, 8:11 am


I did some preliminary performance tests on our new 2634B and the output signals are sadly very interfered. I connected the HI output directly to the scope, with guard left unconnected. LO was bridged to GND. I've found there is a few hundred millivolt ripple, although the signal should be 0 V. The are periodically ringing signals (~130kHz freq.) and quite some noise.

Besides, when sourcing a voltage sweep and using a CC, there are very high voltage peaks induced to the signals - seems like coupled from the relays, which are switching to another current measurement range.

For our devices are ideally defined driving signals very important (influencing the kinetics), which makes this a crucial issue.

I'm wondering if you are aware of this performance, because I doubt this meet the specs of the SMU. Or could that be caused by the setup, incorrect wiring, ground loops or similar?

Please see the attached waveforms.

Thank you.
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Norbert W
Keithley Applications
Keithley Applications
Posts: 228
Joined: October 21st, 2010, 7:18 am
Country: Germany

Re: Interfered output at 2634B

Post by Norbert W » August 7th, 2014, 1:14 am

if you have doubts about your instrument working correctly you can check its performance against its typcial noise specs.
One voltage noise spec is range dependent, e.g. 20 V range, 0.1 ... 10 Hz: 300 uV &c., which you could try to verify by
measurements with the instrument itself; the other one is a 'broadband' 10 Hz to 20 MHz spec for the 20 V range, which
takes a scope which allows a bandwidth reduction to 20 MHz and capable of related peak and rms measurements.

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