THERMAL FLOW METER AND FLOW RATE CORRECTION METHOD

To accurately measure a flow rate even when a type of a fluid passing through piping is changed.SOLUTION: A thermal flow meter comprises: a temperature measuring element 2a arranged on piping 1 to detect a first temperature of a fluid; a heating and temperature measuring element 2b for detecting a second temperature of the fluid; a control unit 13 which causes the heating and temperature measuring element 2b to produce heat so that the second temperature is higher than the first temperature by a fixed value; a power measuring unit 7 which measures power consumption of the heating and temperature measuring element 2b; a flow rate derivation unit 8 which converts the power consumption to a flow rate value; a flow rate correction unit 9 which corrects the flow rate value; a storage unit 10 in which first zero-point power consumption in a state where the piping 1 is filled with a reference fluid and the reference fluid stops flowing is stored; a zero-point power ratio calculation unit 11 which calculates a zero-point power ratio from second zero-point power consumption in a state where the fluid in the piping 1 stops flowing and the first zero-point power consumption; and a setting unit 12 which calculates a correction coefficient from the zero-point power ratio and sets it to the flow rate correction unit 9.SELECTED DRAWING: Figure 16 【課題】配管を流通する流体の種類が変わった場合でも精度良く流量測定する。【解決手段】熱式流量計は、配管１に配設され、流体の第１の温度を検出する測温素子２ａと、流体の第２の温度を検出する発熱・測温素子２ｂと、第２の温度が第１の温度よりも一定値高くなるように発熱・測温素子２ｂを発熱させる制御部１３と、発熱・測温素子２ｂの消費電力を測定する電力測定部７と、消費電力を流量の値に変換する流量導出部８と、流量の値を補正する流量補正部９と、配管１内が基準の流体で満たされ、基準の流体の流れが停止しているときの第１のゼロ点消費電力を記憶する記憶部１０と、配管１内の流体の流れが停止しているときの第２のゼロ点消費電力と第１のゼロ点消費電力からゼロ点電力比を算出するゼロ点電力比算出部１１と、ゼロ点電力比から補正係数を算出して流量補正部９に設定する設定部１２を備える。【選択図】 図１６