| 摘要 |
<p>PURPOSE:To suppress the variance of the zero point due to the change of the heater temperature by calculating the differential voltage between an average measured voltage for turning-on of a heater and an off-state reference voltage for turning-off of the heater to correct the variance of the former voltage. CONSTITUTION:An operational amplifier U7 outputs the average measured voltage obtained by weighting and averaging output voltages VU and VD of temperature sensors RD and RU in fixed resistances R1 and R2, and an output voltage VOFF of the amplifier U7 obtained by turning on a switch S4 at the time of setting the flow rate to zero and turning off the heater is stored as the off-state reference voltage in a capacitor C2. When the switch S4 is turned off at the time of setting the flow rate to zero and turning on the heater, an operational amplifier U8 outputs the stored voltage VOFF, and an operational amplifier U9 outputs the differential voltage between outputs of operational amplifiers U7 and U8 to an operational amplifier U10. The output of the operational amplifier U10 is subjected to voltage division to output a corrected voltage, and a prescribed voltage is inputted to an operational amplifier U6, and the output voltages of sensors RD and RU coincide at the time of the flow rate of zero, and the variance of the flow rate signal level due to the change of the heater temperature is corrected.</p> |
