WaveForms SDK creating offset after amplification with NodeAmplitudeSet

[Jakob]

Hi,
I want to replay a .csv with my Analog Discovery. For that I modified the AnalogOut_Play.py script, but sometimes I got an offset (~0.1V).
I record the output with an external oscilloscope.
For testing I created sinus signals in an array and replayed them, the values are between +/-1V. After amplification with FDwfAnalogOutNodeAmplitudeSet to +/-5V I get an offset of 0.07-0.1V and the offset after the signal is around 0.1V if I replay the signal again with no amplification this offset vanishes again. I recalibrated the device to eliminate this as an error.
A similar thing happens in the Waveforms UI if I select 5V as amplitude for a sinus without running it and i zoom in on my oscilloscope there is an offset of 0.07V if I select 1V as amplitude it vanishes again.
Is this the normal for the hardware and is there a solution for it?
I added pictures, one of the whole range and one zoomed in.
Thank you in advance

[attila]

Hi @Jakob

The AWG has two gain steps which are calibrated separately for each channel. Above 1V amplitude setting high range is used.

[Jakob]

Thank you, I overlooked the second option to calibrate for high gain, I only did it for low gain.
I have another question: I use the BNC adapter to get the signal of the wavegen to my oscilloscope.
If I touch the BNC cable it shows movements on the oscilloscope and sometimes it gets "stuck" and I have to recalibrate the device to eliminate the offset on the oscilloscope.
I want the AD to run independent without having to calibrate if somebody moved it or the cable. Is there a way to avoid that or is there something wrong with the BNC adapter?

[attila]

Hi @Jakob

Try using different BNC cable.
The calibration should stay stable, even the factory calibration should be pretty accurate.
Such shifts indicate contact issue, likely the GND connection, the BNC shield has contact problem. I also have some such bad quality cables.
The adapter has 50R jumpers for AWG output, which should be used when the receiver has 50R termination.
Also note the AD gnd is connected to computer gnd, which could cause ground loop in certain setups.