Hi Folks,
I would like to report a behaviour we are experiencing in all our STS T4 machines.
The observation is a high level of electrical noise when we measure even the GND itself, with DUT and whatever application circuit turned off.
We have done some investigation, changing the main connections of oscilloscope, using different voltage probes or scopes.
Starting from machine unplugged from main power, we just plug the 3-phase and the noise already increases (when plugged, there are some low power circuits still alive to manage the ON button). Then, turning on the machine, few seconds after the noise gets much higher (see pic1, where CH1=diffprobe, CH2= passive single ended probe, CH3= active single ended probe)
FFT shows there are main components roughly around 18-20kHz, 40kHz, 60kHz, 300kHz, 600kHz.
The noise is picked up by single ended probes, much less by differential probes with very short head connection. It does not depend on particular application boards, we tried also measuring directly on STS pogos without any application board and no relevant changes observed.
Suspecting conducted emissions on 3-phase main supply, we tried several configurations of oscilloscope/STS supply and earth connection.
We can only say that it gets improved if we connect the earth of STS to the earth of oscilloscope, but still very high. Amplitude of disturbance changes moving the position of the probe cable with respect to the STS chassis.
The other clean statement is that for sure STS electronics has to do with it, according to what reported above.
Question1: has such noise been experienced by other user?
Question2: are there any particular tricks about how to manage main power connections/earthing (EMI filters or similar) of the STS so to avoid noise/EMI ?
Thanks
