Introduction to the selection, use, and maintenance of thermal mass flow meters
Release time：
06 Jun,2022
Summary
Thermal mass flow meters, also known as calorimetric mass flow meters, are instruments used to measure the mass flow rate of various gases. The basic principle is to use an external heat source to heat the fluid being measured, and the temperature difference caused by the fluid flow reflects the mass flow rate of the gas.
With the continuous development of science and technology, Thermal mass flow meters have been widely used in many fields of scientific research and production. Due to improper user selection or non-standard use, instruments purchased at a high price often fail to fully exert their expected measurement and control effects. This not only affects normal scientific research and production but also causes huge losses to enterprises. Therefore, Qingdao Xinnovis Microsystem Technology Co., Ltd. will summarize and introduce the experience accumulated over the years in the selection, use, and maintenance of thermal mass flow meters for your reference.
There are many domestic and foreign products of thermal mass flow meters, with various models and specifications, but the structural principles are basically the same, and the operation and maintenance are generally similar. Therefore, this article takes Thermal mass flow meters as an example, and introduces the following.
I. Selection of Thermal Mass Flow Meters
1. Suitable Type
Thermal mass flow meters have been developed and applied in China for decades and are now standardized and serialized. There are many representative types, including general-purpose, high-precision, high-pressure, high-flow, low-flow, fast-response, and international standard types. Users can flexibly choose the appropriate type based on the actual needs of their production technology and research conditions.
2. Mass Flow Meter or Controller
A thermal mass flow meter is an analog instrument that can accurately measure the mass flow rate of gas. It features no moving parts, low pressure loss, no temperature compensation, and easy connection to integrators, automatic data recorders, and computers to achieve automatic integration, recording, and computer control. If only flow control is required, a thermal mass flow controller can be selected, which can automatically control the gas flow rate to maintain the user-set flow value.
3. Correct Process
Due to the different units of medium flow rate required in process systems and scientific research, Thermal mass flow meters the provided range refers to the standard state, i.e., under the conditions of 0 temperature and 101325 Pa (760 mmHg) pressure, the standard milliliters per minute or standard liters per minute of ammonia flow rate. Therefore, how to choose the correct flow range is crucial. In addition, improper range selection cannot guarantee appropriate measurement accuracy. The general steps for selecting the flow range are as follows:
(1) Convert the required flow rate in the process to the mass flow rate under standard conditions.
(2) Refer to the mass flow conversion factor provided by the manufacturer to convert the required gas mass flow rate.
(3) Refer to the product specifications provided by the manufacturer to select a standard range product, so that the required actual flow value is less than or equal to two-thirds of the selected instrument range but greater than one-third of the selected instrument range.
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