| 摘要 |
<p>PURPOSE:To improve response by returning a deformed balanced bridge circuit into an ordinary bridge circuit, and changing the connection to a differential amplifier. CONSTITUTION:A balanced type bridge is composed of resistors 1-3 and a heat resistor element 4 for detecting the flow rate of air. The balanced state of the bridge circuit is detected with an operation amplifier 5. For an operation amplifier 10, resistors 7 and 8 and a heat resistor element 9 for compensating temperature are provided. A voltage output V2 as a function of the flow rate of air becomes as follows: V2=R3R7V1/(R7+R8+Rc)(R2+R3)-R7V01/(R7+R8+ Rc)-V02. The effect term VTOFF of the offset voltage in this expression is as follows: VTOFF=R7V01/(R7+R8+Rc)+V02. When R1=10OMEGA, R2=9kOMEGA, R3=400OMEGA, R7=232OMEGA, R8=11OMEGA and Rc=20OMEGA, VTOFF=0.88V01+V02 is obtained. The effect of the offset can be made sufficiently small. Therefore, a hot wire type air flowmeter having a high response speed and excellent characteristics is obtained.</p> |
