Measurement of contact potential by electrostatic excitation of low frequency vibrations

A modulation method is suggested for measuring the contact potential V c between a material and a mechanically sensitive standard surface situated in close proximity. If V c is modulated with a low frequency sinusoidal voltage, the first harmonic of the electrostatic force will depend linearly on V c . This force can be arranged to induce in the sensitive member resonant vibrations of appreciable amplitude which will vanish upon application of a bias voltage which counteracts V c . The residual displacement amplitude may be indicated by any suitable means of vibration detection. The method is direct, rapid, simple and sensitive. The contact potential may be balanced to better than 0.01 v.