| 摘要 |
<p>PURPOSE:To simplify a manufacturing process by providing a resistance difference between a resistance bulb for temperature detection and a resistance bulb for temperature compensation, giving temperature dependency to the temperature difference between the both, and calceling the fluid temperature dependency of a heating resistance. CONSTITUTION:A bridge circuit is formed of fixed resistances Ra and (r), a resistance bulb Rm for a heater, and a resistance bulb Rt for temperature compensation Rt. The output of the bridge circuit is amplified by an operational amplifier 1 and fed back to the heater resistance Rh to make the temperature difference (DELTAt) between the resistance bulbs Rm and Tr constant. here, the heater resistance Rh and resistance bulb Rm are put close and held at equal temperature, and the resistance bulb Rt is put away from the heater resistance Rh and held at the same temperature with the temperature of liquid. The temperature difference DELTAt between the resistance Rm and Rt is set by the fixed resistance (r), but constant irrelevantly to the fluid temperature when the resistances Rm and Tr have the same temperature characteristics. The power consumption (P) of the heater resistance Rh is expressed as P=Vout<2>/ Rh=(A+BXU<1/2>).DELTAt, where U is the flow velocity and A and B are constants. The flow velocity U is calculated from the power consumption P. Consequently, the measurement accuracy is improved.</p> |
