Hi.

I'm conducting the study which requires measuring the surface potential of nonwoven webs using Trek 542A electrostatic voltmeter.

During measurements, I found that measured voltage values for the same spot keep decreasing.

I constantly done calibration for each repeated measurements, and both nonwoven sample and the probe were fixed in the air with insulators.

Is it attributed to capacitive coupling between the sample and probe, or is there any other reason for this phenomenon?

I'll be really grateful for the answers. :)