Abstract: An accelerometer comprises an electric coil pivotally mounted in a magnetic field about an axis extending perpendicular to the field for oscillatory movement substantially perpendicular to the field, in the manner of a D'Arsonval movement. Switching means in the form of a radition source and detector responds to movement of the coil assembly when on either side of a switching position to apply a constant current to the coil to move it in the direction of the switching position, thereby setting up an oscillation of the coil. Linear acceleration is measured by having an inertial mass, such as provided by mounting the coil away from its center of mass, displaced from the pivotal axis. An acceleration force acting on the mass of the oscillating coil alters the proportion of time spent at each side of the switching position to give an average current flow in the coil related to the magnitude of acceleration. More than one coil may be provided to measure acceleration along a number of axes.

Abstract: A distance measuring arrangement has an accelerometer transducer of the force balance type in which a switch closed by the action of an acceleration force causes a constant current to flow in a coil to oppose the force and open the switch. The switch opens and closes in a repetitive cycle at the resonant frequency of the system, the closed switch gating clock pulses to integration means. The transducer may take two forms. In the first the proportion of time that the switch is closed in each cycle is proportional to the acceleration value. Distance measurement comprises counting the clock pulses to effect a first stage of integration and summating the counter totals every 1000 clock pulses to give a distance travelled signal. In the second, the proportion of time that the switch is closed in each cycle is proportional to the square root of the acceleration value and distance measuring comprises counting the clock pulses to give a signal proportional to the square root of distance travelled.