Method for improving measurement accuracy of thermal mass flowmeter by means of dynamic temperature compensation

Abstract

The invention provides a method for improving measurement accuracy of a thermal mass flowmeter by means of dynamic temperature compensation. The method includes the steps: measuring heating current Ih00 of a self-heating RTD (resistance temperature detector) at the temperature T0 during zero flow; setting heating current Ih0T of the self-heating RTD at set temperature T during zero flow; defining a current conversion coefficient K=(Ih0T / Ih00)<2>; measuring heating current of the self-heating RTD under at least two discrete temperature spots; solving current conversion coefficients under the corresponding discrete temperature spots through a current conversion coefficient formula K; acquiring a continuous relation function K=f(T)of the temperature and current conversion coefficients through the discrete temperature points; solving current of the self-heating RTD at any reasonable temperature during zero flow; dynamically adjusting the Ih0 through a flow calculation formula Flow=f(Ihot, Ih0) according to difference of fluid temperature. By the method, the defect that measurement accuracy of existing thermal flowmeters is affected by the fluid temperature is overcome, and the fluid in a wider temperature range can be measured under the premise that precision is guaranteed.

Description

【Technical field】 [0001] The invention relates to a thermal mass flow meter measurement method, more precisely a method for improving the thermal mass flow meter measurement accuracy through dynamic temperature compensation. 【Background technique】 [0002] The thermal mass flowmeter uses the principle of heat transfer, that is, the heat exchange relationship between the flowing fluid and the heat source (the object heated in the fluid or the heating body outside the measuring tube) to measure the flow rate. It is currently mainly used to measure gas. Thermal mass flowmeter has the function of directly measuring gas mass flow, simple composition, small failure probability, wide range, fast response, high precision, low flow rate sensitivity, direct mass flow measurement, on-site display, signal output, upper and lower limit alarms, and various structures , divided into plug-in type and pipeline type installation, flexible installation, convenient loading and unloading, easy t...

AI Technical Summary

Problems solved by technology

Furthermore, if the temperature of the measured fluid changes dynamically, the error of Ih0 will also change dynamically with the change of temperature, resulting in the error of the final measurement result will also change dynamically

In short, the current German-American thermal mass flowmeter will cause the measurement accuracy to be affected by the temperature of the measured fluid due to the fixed Ih0

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