This is the most critical step. Static meters measure the potential difference between the sensor and ground.
To maintain precision, the sensor—which is the most sensitive part of the instrument—must be kept free of contaminants like water, oil, or solvents. Operation/Maintenance FMX-003 Electrostatic Fieldmeter simco fmx002 manual top
The internal chopper (vibrating shutter) is failing or the top PCB connection is loose. Fix: This is the most critical step