| 摘要 |
<p>PURPOSE:To drive a thermal type flowmeter with a low driving voltage, to make it small in size, to make the sensitivity thereof excellent and to reduce the manufacturing cost thereof, in regard to the thermal type flowmeter which detects a flow rate, flow velocity, etc., by executing temperature compensation of a fluid temperature. CONSTITUTION:A bridge side output voltage V11 is taken out from the side of a temperature-sensitive resistor 3 for temperature compensation of a bridge circuit 30 and given to an inverted input terminal of a differential amplifier 7, while a bridge side output voltage V12 is taken out from the side of a temperature-sensitive resistor 2 for detection and given to a noninverted input terminal of the differential amplifier 7. A differential output voltage V12-V11 is given to a resistor 4 for heating and, thereby, a control is made so that a temperature difference between the two temperature-sensitive resistors 3 and 2 are fixed. The differential output voltage given to the resistor 4 for heating becomes a detection signal of a flow rate. The resistor 4 for heating and the temperature-sensitive resistor 2 for detection are made to have a thermally integrated structure. Thereby a device is made small in size, a drive circuit is also made simple and, thereby, the manufacturing cost is reduced.</p> |
