Abstract: A digital circuit for adapting the output of a closed-loop accelerometer to a utilization circuit where the cycle time of the rebalance loop of the accelerometer is unrelated to the cycle time of the utilization circuit. A register receives and stores a digital value representative of measured acceleration and a bank of serially-arranged divide-by-two counters accepts the output of the rebalance loop clock. A gate arrangement makes one-by-one correlations between the states of the register and the outputs of the divide-by-two counters. A trigger circuit receives the gate outputs, providing a pulse when triggered by a downgoing edge of a square wave output of the gate array. A counter receives the pulse stream and is gated, in turn, in accordance with the cycle time of the utilization circuit so that the accelerometer data employed therein is representative of the portion of the acceleration occurring during a cycle of the utilization circuit.

Abstract: A force balanced accelerometer system comprises an accelerometric sensor and a control system. The sensor comprises a conductive pendulum pivotably mounted between first and second electrode plates. The control system establishes a cycle period with three phases. In the first phase, the pendulum is electrically isolated in an electric field established between the electrodes. The pendulum is moved from a null position in response to inertial acceleration, and a pickoff signal indicative of the acceleration-responsive position is generated. The pickoff signal is fed into a sample-and-hold circuit and then into a servo compensation circuit, having proportional and integral control, so as to generate a force-indicative signal indicative of the magnitude and direction of the force required to restore the pendulum to the null position.

Abstract: An electrostatically force balanced accelerometer employs electrostatic, single sided square law forcing after filtering and scaling the pickoff signal to determine a restoring force required to bring the pendulous mass (10) of the accelerometer back to its null position. A signal (44,48) proportional to the square root of the restoring force is applied to an electrostatic square law forcing circuit (50) that applies a restoring force to one side or the other of the pendulum (10). A system output signal (42) is proportional to the calculated restoring force, and thus linearly proportional to the sensed acceleration. The transfer function of the forcing circuit (50) is empirically determined by applying a series of known accelerations and measuring the balancing signal required to restore the pendulous mass (10) to its null position.