GB832411A - Improvements relating to circuits for counting electrical pulses emitted in the sensing of fluid flow - Google Patents

Abstract

832,411. Total flow meters. SIMMONDS AEROCESSORIES Ltd. Aug. 13, 1958 [Aug. 21, 1957], No. 26397/57. Addition to 803,070. Class 40 (1). A " cup and bucket " pulse counting circuit as claimed in the parent Specification, is adapted for metering fluid flow by counting the pulses emitted by a flow sensing unit at a frequency dependent on flow rate. It includes a potentiometer manually adjustable in accordance with the density of the liquid and a thermistor network so that, with the potentiometer set for a given liquid, the count is given in terms of mass flow independently of temperature variations of the fluid. The Figure shows a fluid-flow meter in which pulses from a flow meter sensing unit S of the type described in Specification 803,069 causes pulses to be emitted from a pulse generator 1 in dependence upon the fluid flow. These are fed to a " cup and bucket pulse counter comprising an integrating capacitor 5, the charge upon which increases incrementally with each pulse from generator 1 until at a given charge level tube 7 conducts to trigger device 18 and operate relay 17, the armature of which is connected with a mechanical counter C. The point at which diode 25 conducts is determined by the setting of potentiometer 30 which is coupled to a calibrated dial 32 and set according to the specific gravity of the fluid whose flow is to be measured. The point of conductivity of diode 25 depends also upon the thermistor network 34, 35, the resistance of which depends upon the temperature of the fluid. In this way the count is dependent on the mass of liquid flowing and automatically compensates for changes in density due to temperature variation. The circuit may be combined with a rate of flow meter as described in Specification 832,412. The potentiometer and thermistors may be used to vary the reference voltage applied to terminal 6 by connecting them in series in a bleeder resistance chain connected across the H.T. supply or they may be used to control the amplitude of pulses from the pulse generator 1.