| 摘要 |
PROBLEM TO BE SOLVED: To accurately carry out the thermal measurement of a flow rate, by improving the noise ratio of a spot temperature rise signal mounting to several % of a working environmental temperature. SOLUTION: In order to measure the flow velocity of a fluid, a heater 26th arranged on the upstream side of a passage 25 for raising a spot temperature against the fluid and a plurality of thermistors 26t-1, 26t-2 are separately disposed from each other by an already-known distance L. Besides these thermistors, a thermistor 26e to measure an environmental temperature is disposed near the passage 25 to amplify a difference between the thermistors 26t-1 and 26t-2 with an amplifier 14 for amplifying differential input flow rate signals. Thereby taking out signal components corresponding to only the spot temperature rise, a detection time difference Δt is calculated based on these signals and subsequently a required flow velocity is calculated by dividing the distance L by the time difference Δt. |
