GB1089860A - Method and apparatus for measuring the mass flow rate of gaseous hydrocarbons - Google Patents

Abstract

1,089,860. Measuring mass flow-rate of gases ROCHAR ELECTRONIQUE. June 23, 1965 [June 24, 1964], No. 26651/65. Heading G1N. The mass flow-rate of a gaseous hydrocarbon is determined electrically by measuring the volumetric rate of flow, using a Venturi, and determining the apparent density p a using a known relationship between the upstream pressure P and temperature T. The inverse of # a is given by W = k o T/P + Y(T), where the function Y(T) is predetermined experimentally. The upstream temperature T is measured electrically at 40, and the signal voltage applied to a rheostat 38. The upstream pressure P is measured at 30 and the slider of rheostat 38 adjusted accordingly to give T/P. The constant k o of the above equation for W is obtained by the feedback amplifier 44 to give k o T/P. The temperature signal T is also fed through a function generator 48 to give Y(T). These components are added at 50 to give W = k, T/P + Y(T). The mass flow-rate D m is given by D m = C#fa.#P = C##P/W, where C is a constant, and #P is the differential pressure measured across the Venturi constriction at 18, 20. A monostable multi-vibrator 58 has its pulse frequency F determined by a voltage/frequency converter 54, and pulse duration controlled at electrode 60 by the signal W. The output is integrated at 62 to give FW, and used to control the pulse duration of a second, similar monostable multi-vibrator 64 whose pulse frequency is also F, the output being integrated at 68 to give F<SP>2</SP> W. This signal is composed with the differential pressure signal #P measured at 26 in a feedback loop to make them equal. Thus #P = F<SP>2</SP> W or F = ##P/W, making F proportional to D m , the mass flow-rate. The frequency F is measured at 70, and integrated by a pulse counter 72 to give the total flow weight.