| 摘要 |
<p>PURPOSE:To reduce the gas temperature dependence and thus increase the accuracy of measurement, by controlling the current flowing to the heater so as to secure a constant output for the bridge circuit consisting of the temperature dependent resistance and the reference resistance provided at the upper and down streams of the heater. CONSTITUTION:The bridge circuit is formed with the temperature dependent resistance 10 plus the reference resistances 21 and 22 provided within the flow rate measuring tube 9, and the output ends (a) and (b) of the bridge circuit are supplied to the electric power amplifier 7c via the differential amplifiers 7a and 7b each. Then the output of the amplifier 7c is connected to the electric heater 10 via the bridge circuit and the resistance 7d. In the voltage control circuit 17 thus constituted, the current flowing to the heater increases unitl the output of the amplifier 7b becomes 0 with increment of the sucked air and reduction of the temperature difference between the resistances 9 and 10. And the current flowing to the heater decreases with reduction of the absorbed air. The relation shown by the equation is secured between the current I flowing to the heater and the amount G of the sucked air. As a result, the amount of the sucked air can be obtained by measuring the voltage V0 of the output resistance 7d.</p> |
