ULTRASONIC FLOWMETER AND FLOW RATE COMPUTATION METHOD

To enable measurement errors to be reduced compared to before, even when flow rate measurement is conducted using a zero-cross point.SOLUTION: The present invention comprises: a received signal acquisition unit 401 and a received signal acquisition unit 402 for acquiring a received signal; a zero-cross point measurement unit 403 and a zero-cross point measurement unit 404 for measuring the time till a zero-cross point multiple times for each of a plurality of unit measurement steps; a time difference calculation unit 405 for calculating a time difference between measurement results from the zero-cross point measurement unit 403 and measurement results from the zero-cross point measurement unit 404; an average value calculation unit 406 for calculating the average value of time differences at the first-half zero-cross point; an average value calculation unit 407 for calculating the average value of time differences at the latter-half zero-cross point; a difference calculation unit 408 for calculating the difference between calculation results from the average value calculation unit 406 and calculation results from the average value calculation unit 407 as a correction value; and a flow rate computation unit 409 for computing the flow rate of a fluid which is the object to be measured, on the basis of calculation results from the time difference calculation unit 405 and the correction value calculated by the difference calculation unit 408.SELECTED DRAWING: Figure 2 【課題】ゼロクロス点を用いて流量計測を行う場合でも、従来に対して計測誤差を低減可能とする。【解決手段】受信信号を取得する受信信号取得部４０１及び受信信号取得部４０２と、複数の単位計測工程毎に、ゼロクロス点までの時間を複数回計測するゼロクロス点計測部４０３及びゼロクロス点計測部４０４と、ゼロクロス点計測部４０３による計測結果とゼロクロス点計測部４０４による計測結果との時間差を算出する時間差算出部４０５と、前半ゼロクロス点での時間差の平均値を算出する平均値算出部４０６と、後半ゼロクロス点での時間差の平均値を算出する平均値算出部４０７と、平均値算出部４０６による算出結果と平均値算出部４０７による算出結果との差分を、補正値として算出する差分算出部４０８と、時間差算出部４０５による算出結果及び差分算出部４０８により算出された補正値に基づいて、測定対象である流体の流量を演算する流量演算部４０９とを備えた。【選択図】図２