A prototype device to calibrate recording Earth tide meters of the TRG-1 variety has been constructed and demonstrated to operate satisfactorily. The calibration is effected by subjecting the gravimeter to an external sinusoidal acceleration of approximately 3 [j.m/s2. The magnitude of the applied acceleration, which is determined from a record of the gravimeter's displacement, is compared directly with the gravimeter's response. The prototype was limited to a driving frequency of 0.01 Hz. The

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... econstruction of the calibrator to permit operation at frequencies down to 0.001 Hz is discussed. A calibration precision of 0.1 % was achieved with the prototype. R eferences (Valliant)