| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To fully secure accuracy in flow rate detection, even when environmental temperature varies and to hold down the nonuniformity in sensitivity among products, without providing a process for sensitivity correction before shipment of the products, in a thermal flow sensor which detects the flow rate of a test fluid, using a heat resistor and a pair of thermometric resistors. <P>SOLUTION: The heat resistor is energized by a periodic on-off driving and a voltage Vs to be a sensor output is calculated based on a temperature difference output Vb which is a detection signal of a temperature difference between the paired thermometric resistors. Here, the on-off driving is conducted with the time from a time point ton where the energization of the heat resistor is turned on to a prescribed time point t1, before saturation of the value of the temperature difference output Vb made a half period T/2, and the voltage Vs is calculated, based on the amplitude of the temperature difference output Vb outputted as an alternating current signal at this time. At the calculation, the temperature correction is performed by dividing the value, showing the amplitude of the temperature difference output Vb by the average value Vave of the temperature difference output Vb. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
