| 摘要 |
PROBLEM TO BE SOLVED: To provide a sensor which has both functions as a flow velocity sensor and a thermal conductivity sensor in the same circuit, and which switches between the functions to enable the functions to be individually used.SOLUTION: The sensor with two functions comprises: a heater driving circuit 1 having at least a heater element RH of which a voltage between terminals changes according to a flow velocity of a fluid, a temperature sensor RR of which a voltage between terminals changes according to an ambient temperature of the fluid, and an operational amplifier U1 for outputting a measured potential according to a difference between a reference potential Vr and a heater potential Vh that is the voltage between terminals of the heater element RH; a constant voltage circuit 2 for outputting a constant voltage; and a switch SW1 for switching between supply of the constant voltage and supply of the voltage between terminals of the temperature sensor RR, to the operational amplifier U1 as the reference potential Vr. When the voltage between terminals of the temperature sensor RR is supplied as the reference potential Vr, the sensor operates as a flow velocity sensor varying in a measured potential OUT according to the flow velocity of the fluid. When the constant voltage is supplied as the reference potential Vr, the sensor operates as a thermal conductivity sensor varying in the measured potential OUT according to thermal conductivity of the fluid. |
