GB969061A - Improvements in or relating to the measurement of heat - Google Patents

Abstract

969,061. Measuring heat electrically. SATCHWELL CONTROLS Ltd. Jan. 1, 1963 [Jan. 8, 1962], No. 730/62. Heading G1N. Apparatus for measuring the heat supplied to a radiator in a fluid heating system comprises electrical means for measuring the temperature change in the fluid due to the heat load, electrical means for determining the mass flow of the fluid, and combining these signals to get the total heat supplied to the radiator. As shown (Fig. 1), the rate of fluid flow through a feed pipe 1 is measured in a by-pass conduit 4 associated with the return pipe 3, the proportion of the fluid flowing through the bypass being adjustable by dampers 7, 8. The bypass 4 contains two temperature-sensitive resistors 9, 10 connected into a bridge circuit 11 where unbalance current, amplified at 13, feeds a resistor 14 located between resistors 9, 10 with sufficient current to bring the temperatures of resistors 9, 10 substantially into agreement. The heat supplied to resistor 14 is then proportional to the mass flow of fluid through pipes 1, 3, 4. Two further temperature-sensitive resistors 15, 16 are located in the go and return conduits to the radiator 2, and are connected in series with current coils 17, 18 respectively of an energy meter 20, the two series circuits and the pressure coil 19 of the meter being connected across resistor 14. It is shown that the reading on meter 20 is proportional to the total heat supplied to the radiator 2. Errors due to heat loss from the by-pass conduit 4 are neutralised by a heater 14a operating at a constant rate, or the conduit 4 is itself heat insulated. In a modification (Fig. 2) the resistors 15, 16 constitute two arms of a bridge A fed with a constant voltage, the bridge output, which is indicative of the temperature difference in the go and return conduits, being fed via an amplifier 13a to the current coil 18 of meter 20. Specification 968, 518 is referred to.