| 摘要 |
PURPOSE: To solve the conventional problem wherein a circuit constitution is complicated and miniaturization of a device is difficult. CONSTITUTION: This device is equipped with a bridge circuit constituted from upstream-side and downstream-side temperature detection elements 1, 2 for detecting the temperature of fluid flowing from the upstream side to the downstream side and fixed resistances 5, 6, and a temperature difference control circuit for supplying a power continuously to upstream-side and downstream-side heating elements 3, 4 so that the temperature difference between the elements 1, 2 becomes a prescribed value. The temperature difference control circuit has a differential amplifier 10 connected to the bridge circuit, a first constant-voltage power source 16, a second constant-voltage power source 14 having a lower voltage than the first constant-voltage power source, and the upstream-side and downstream-side heating elements 3, 4. The upstream-side heating element 3 is connected between the output side of the differential amplifier 10 and the second constant-voltage power source 14, and the downstream-side heating element 4 is connected between the output side of the differential amplifier 10 and the first constant-voltage power source 16. Thus, a flow rate signal of an analog voltage capable of discriminating the flow direction and having an excellent SN ratio can be acquired.
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