Abstract: An air-bearing gage tip or pad for a gage head is mounted on a swivel and closely follows the surface of a non-porous material without touching the surface and accommodates undulating surfaces which approach the pad at an angle and also small errors in mounting the pad normal to the surface, and additionally accepts small imperfect, surface perturbations without loss of air. The air-bearing pad features advantages in respect of increase in bearing stiffness and increase in mechanical response of the gage head and improvement in freedom from adverse effects encountered in the prior art and tending to be caused by thermal shifts and inherent hysteresis.

Abstract: A piezoelectric flexible arm member is mounted to a base at one end and supports a torque coil in a magnetic field at its other end. The torque coil comprises a seismic element disposed to be moved in accordance with acceleration forces applied thereto. A voltage is produced across the piezoelectric flexure arm when movement of the torque coil causes it to flex. The torque coil may include means to induce a signal in a position detector circuit representative of the position thereof. Both the signals from the piezoelectric member and the position detector may be used as error signals in a servo amplifier system to provide restoring forces to the torque coil and to produce an output signal representative of acceleration forces. A third conventional error signal may also be employed in the system.

Abstract: A servo amplifier system includes first and second operational amplifiers, with the second amplifier having a low output impedance. A torque coil is connected directly from the output circuit of the first amplifier to the input circuit of the second amplifier free of any impedance elements which would tend to make the torque coil subject to frequency response variations. Various circuits are provided to feed back error signals from the output circuit of the second amplifier to the input circuit of the first amplifier. A test signal may be connected across torque coil to test the response of the accelerometer including the torque coil.

Abstract: A servo amplifier system for an accelerometer includes a torque coil. A torque coil is included in the output circuit of a first amplifier. A position sensor circuit develops a signal corresponding to the position of the coil which is applied to the input circuit of the first amplifier. An element, which may be a resistor, senses the current through to the coil and produces a voltage which is applied to a second amplifier having a low impedance output circuit. The output signal from the second amplifier is fed back to the input circuit of the first amplifier. Means are associated with the second amplifier to comply with the scaling and bandwidth requirements of the system.