| 摘要 |
<p>PURPOSE:To perform high-precise measurement through simple constitution by providing a voltage proportional to a velocity of flow in a way that a multifunction computing circuit and voltage converting circuit are located in a negative feedback circuit for keeping a tempera ture difference between temperature sensitive elements on the upper and downstream side of a heat type mass flow meter at a constant value. CONSTITUTION:Heat sensitive resistance wire sensors S1 and S2 are located on the upper stream and the downstream side of a heat conductive flow pipe with a distance therebetween being long enough to allow prevention of the occurrence of heat interference with each other. Outputs from the sensors S1 and S2 through a bridge circuit containing the sensors S1 and S2 are compared with each other by a comparing amplifier 1, and from a comparing result, a velocity of flow is detected. Feedback control is made on the bridge circuit so that the temperatures of the sensors S1 and S2 are adjusted to a constant value. A multifunction computing circuit 2 and a pressure converting circuit 3 are arranged to a feedback circuit, and perform computation according to a relation formula between the output voltage of a heat type flow meter and a flow rate or a velocity of flow. Feedback of an a-constant, m 1, and an output E1 based on a relation E0=aE1<m> between outputs E1 and E2 to the bridge circuit is effected. This constitution provides a voltage always proportional to a velocity of flow based on a sensor output of the n-th power characteristics of a flow rate and measures a high-precise flow rate through simple constitution.</p> |
