A method and a system for calibrating the work function or surface potential of a non-contact voltage sensor probe tip. The method includes preparing one or more reference sample surfaces and a reference non-contact voltage sensor probe tip to have stable surface potentials, measuring the voltage between the reference samples and the reference sensor probe tip, measuring the voltage between a point on a non-reference sample surface and the reference sensor probe tip, measuring the voltage between the same point on the non-reference sample surface and a non-reference non-contact voltage sensor probe tip, and determining a surface potential correction factor for the non-reference, non-contact voltage sensor.