Thermal flow sensor with reduced errors in measurement - comprising heat sensitive electrical resistance, holder, bridge circuit, and control switch

摘要

Thermal flow sensor (I) comprises (a) a heat sensitive, electrical resistance (3) having an electrically insulating base, a heat sensitive resistance element (32) arranged on a holder and comprising a resistor that changes with temp. corresp. to a predetermined temp. coefft.; (b) a holder to hold the base inside a flow of a fluid; (c) a bridge circuit having a heat sensitive resistance and several other resistances; and (d) a control switch to control the bridge circuit so that the bridge circuit maintains a predetermined equilibrium state, and to establish the flow of fluid from the equilibrium. The heat sensitive resistance element has a heat sensitive main section of 1st resistance temp. coefft., and a thermal buffer section of 2nd resistance temp. larger than that of the 1st. The thermal buffer section is arranged near to the holder. The heat sensitive electrical resistance is also claimed. ADVANTAGE - Errors in measurement, resulting from heat irradiation from the heat sensitive resistance, are kept to a minimum.