This paper describes a simple method for calibrating a Willmore geophone without using a shake table. It is assumed that one of the mechanical parameters of the system is known—in this case, the mass. The results from this simplified method are compared with an a.c. bridge method in which the equivalent electrical impedance is measured and with another bridge method described by Willmore where the sensitivity is measured by a substitution method. The three methods give substantially the same sensitivity of 6.1 volts/cm/sec for the particular geophone, with an estimated accuracy of 2 per cent, and all agree to the manufacturer's approximate specification to within 7 per cent.

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