Equipment has been built for measuring vibratory displacements of very small mechanical elements such as phonograph styli and piezoelectric crystals. It employs a probe of small dimensions so that virtual point measurements may be made. The probe does not contact the point under measurement and therefore imposes no mechanical load. The variation in capacitance between probe and vibrating surface is used to measure the displacement. Through the use of a built-in calibrator, the sensitivity may be adjusted electrically for direct meter reading of vibratory displacement without resorting to precise adjustment of condenser plate spacing. Displacement amplitudes of less than 10−6cm may be measured. The output signal corresponds accurately to the displacement both in magnitude and in phase over a wide frequency range, so that complex vibrations are portrayed accurately on a cathode-ray oscilloscope. The equipment has been calibrated by four independent methods, including a reciprocity method, with close agreement.