Patent ID: 6928865
Filing Date: 2005-08-16
Classification: G01F

Abstract:
1. A thermal flowmeter having not only a sensor channel over which resistors for measuring a flow rate are mounted bridgewise but also a bypass channel relative to the sensor channel, the thermal flowmeter comprising: a body having a shape which is symmetric right and left; a laminate having a shape which is symmetric, the laminate being fitted in the body to divide a fluid into a fluid portion flowing into the sensor channel and a fluid portion flowing into the bypass channel; an upstream temperature sensing resistor disposed in the sensor channel on an upstream side in a fluid flowing direction; a downstream temperature sensing resistor disposed in the sensor channel on a downstream side in the fluid flowing direction; a heating resistor disposed between the upstream temperature sensing resistor and the downstream temperature sensing resistor to heat the upstream temperature sensing resistor and the downstream temperature sensing resistor; a fluid temperature sensing resistor for sensing the temperature of a fluid under measurement; and an electric circuit which makes a control so that the heating resistor and the fluid temperature sensing resistor show a constant difference in temperature and which measures the flow rate of the fluid under measurement based on a temperature difference between the upstream temperature sensing resistor and the downstream temperature sensing resistor.