A self-zeroing geophysical strainmeter design is described which has been used extensively by Cambridge University in the past 4 years. The performance of the buried 10-m instrument is adequate to study geophysical signals in the Earth at periods from 1 sec to DC and with magnitudes from 10-10 to more than 10-5 strain. Low current consumption enables the instrument to operate remotely from batteries for up to 1 year. Better than 0.1 per cent linearity allows its use in the study of nonlinear geophysical signals, and relative calibration to 0.2 per cent allows clusters of instruments to be used in arrays. The absolute calibration of such an array is 2 per cent.

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