GB1113992A - Improvements relating to weighing instruments - Google Patents

Abstract

1, 113, 992. Measuring weight electrically. SPERRY RAND Ltd. April 1, 1965 [April 1, 1964] No. 13373/64. Heading G1N. A weighing instrument including means for compensating for the effect of acceleration comprises a first force coil 2 mounted in a magnetic field, a variable resistor 5 which controls the current in the coil so that the force produced by the coil counterbalances, at least in part, the weight to be measured, an accelerometer 6 having a second force coil 7 tending to maintain the movable element of the accelerometer in a datum position, a feedback loop 8, 9 which applies a voltage representing the sensed acceleration to the coil 7, and a circuit which applies across the variable resistor 5 a voltage which is a function of the acceleration-representing voltage. The instrument may be a continuous flow densitometer in which the liquid passes through a horizontal U-tube pivotally mounted on flexible connections and supported by the force coil 2. Movements of the object to be weighed are detected by an inductive or photo-electric pick-off 3 which delivers a signal to a servo system 4 controlling the variable resistor 5, and the voltages appearing across the resistor 5 and a fixed resistor 10 in series with the coil 7 are added by resistors 11, 12 and supplied to an amplifier 13 which provides the current to the coil 2. The circuit maintains the voltage across the resistor 5 substantially equal to the reference voltage across the resistor 10, so that the setting of the resistor 5 is proportional to the weight to be measured and is independent of the acceleration of the instrument.