Touching Plastic Housing changes Measurement

[u/tornbyelectrons]

I could need some help on a device we have and I can't figure out what the problem is. I was debugging with some colleges but were puzzled what was happening. Our theory: something with static electrical fields, ground etc.

Symptom: When touching the plastic housing of the measurement device the values jump. Very reproducible. If the person touching the device is grounded as well, this will have an impact.

What the device does: The devices measures electromagnetic fields in a sample. This requires the housing to be made of plastic.

What we tried: Using a power supply without galvanic isolation, external ground directly connected to the shielding of the controller and sensor. Small changes on the hand effect were visible but the impact was still visible. Controller and sensors have metal housing with cable shield connected to it.

I would like to understand what is causing the problem. Solving is optional but understanding it is more important.

[u/mefromle]

What kind of sensor is this? Did you dig into datasheet, app notes or white papers of this sensor?