Apparatus for measuring the electron escape potential of metal surfaces

In apparatus for measuring the electron escape potential of a metal surface which includes a conductive plate disposed is closely spaced parallel relation to a metal surface at which the electron escape potential is to be measured;

• means for vibrating said conductive plate in a direction vertical to said metal surface;
• circuit means connected to said conductive plate for measuring the potential difference between said metal surface and said conductive plate and including first mechanism for indicating such potential difference;
• the improvement which comprises:
• external circuit means including a source of potential, divider means connected across said source of potential and including an adjustable tap connected to said metal surface, and second mechanism for indicating the potential difference between said tap and said source of potential;
• and
• switch means for temporarily connecting said conductive plate to said source of potential prior to measurement to charge the capacitor defined by said conductive plate and said metal surface;
• said adjustable tap being adjusted during measurement to zero the indication of said first mechanism whereby said second mechanism directly indicates the electron escape potential of said metal surface independent of the precise spacing between said conductive plate and said metal surface.