The Charge Sensor, order code CRG-BTA, $79 contains several capacitors which ideally should maintain a constant state when the test leads of the sensor are in electrostatic equilibrium. However, environmental conditions such as local humidity, nearby static charges, etc. may cause the reading to rise or fall surprisingly in a short period of time. A unit that behaves perfectly one day may show a changing value the next day under otherwise identical circumstances.
Our recommendation is to test for zeroing by connecting the sensor to an interface, starting the data collection program, and collecting data while zeroing the sensor by holding the sensor button down for at least 10 seconds. If the sensor does not zero properly, please contact Vernier Technical Support at 888-837-6437 or firstname.lastname@example.org for assistance.
Once the sensor is zeroed, connect it to the Faraday cage and pail of the Electrostatics Kit, order code ESK-CRG, $119. Do an experiment with the sensor to measure some quantity of charge. If the slope of the graph is making it challenging to read the amount of charge from the graph, there is a way to add a correction to the data using a special Logger Pro file (This file is not available for LabQuest or Graphical Analysis).