FREE-MASS RECIPROCITY CALIBRATION

A simple method for reciprocity calibration of accelerometers and velo city sensors is presented. The useful frequency range is from about 1 Hz to a kilohertz or more and the method is capable of subpercent accu racy. Calibrations with excitation levels from 1 to 300 mm/s(2) (0.1 m g to 0.03 g) were produced in prototype fixtures. The device to be cal ibrated and two geophones are used in the calibration fixture. Since t he geophones are both reciprocal, a direct test of reciprocity can be done prior to the calibration to evaluate the apparatus. In contrast t o standard techniques, the method requires only one relatively inexpen sive mechanical setup.