Thermal flowmeter

Abstract

A thermal flowmeter comprises a thermal flow sensor having first and second temperature detection elements (Ru, Rd) disposed in the direction of flow of fluid with a heater element (Rh) disposed therebetween, a first temperature sensor (12a) for detecting the temperature of the fluid flowing in a pipe (10), a second temperature sensor (12b, 12c) for detecting the pipe temperature, wherein the flow rate of the fluid is measured from the difference in detection output between the first and second temperature detection elements, while the amount of flow rate correction is found from a temperature difference correction table (24) according to the difference between the pipe temperature and the fluid temperature, the amount of flow rate correction being used to correct the measured fluid flow rate, which correction is capable of eliminating the thermal effect on flow rate measurement from the external environment so as to improve the measurement accuracy.

Description

technical field [0001] The present invention relates to a flow meter, in particular to a thermal flow meter capable of measuring the fluid flow in a pipeline without being affected by the external environment and with high precision. Background technique [0002] The cumulative flowmeter includes a flow sensor for measuring the instantaneous flow rate of the fluid flowing through the fluid channel, and the cumulative flow rate is measured according to the instantaneous flow rate, which is expected to have high measurement accuracy. In particular, since the gas meter accumulates the instantaneous flow rate of gas flowing through the gas pipe over a month, for example, to measure the gas usage amount (cumulative flow rate) used as the basis for calculating the gas usage fee, it requires high measurement. precision. [0003] Therefore, a thermal flow sensor with high measurement accuracy is generally used in an accumulative flow meter such as a recent gas meter. Thermal flow ...

AI Technical Summary

Problems solved by technology

Therefore, when the detection temperature of the temperature detection element Rr is affected by the external environment and cannot be accurately measured, and the heating temperature of the heating element Rh deviates from the specified temperature, an error occurs in the flow measurement by the thermal flowmeter.

Images