In chemical production workshops, the ratio of raw material gases determines product quality; In the field of environmental monitoring, exhaust gas flow data is related to the effectiveness of environmental governance... In these scenarios, thermal gas mass flow meters have become a "hot commodity" in the industry due to their ability to accurately measure gas flow without temperature and pressure compensation. And the circuit system behind it is the "smart brain" that achieves this outstanding performance. Today, we will take you to explore it!
The thermal gas mass flowmeter is designed based on the principle of thermal diffusion, and uses the constant temperature difference method to accurately measure gases. It has the advantages of small size, high degree of digitization, easy installation, and accurate measurement.
Circuit core module:
Sensor circuit:
The sensor part consists of two reference level platinum resistance temperature sensors. When the instrument is working, one sensor continuously measures the medium temperature T1; the other sensor self heats up to a temperature higher than the medium temperature T2 and is used to sense fluid flow velocity, known as a velocity sensor. The temperature Δ T=T2-T1, T2>T1. When a fluid flows through, the gas molecules collide with the sensor and take away the heat of T2, causing the temperature of T2 to decrease. To keep Δ T constant, the power supply current of T2 needs to be increased. The faster the gas flow rate, the more heat is taken away. There is a fixed functional relationship between the gas flow rate and the increased heat, which is the principle of constant temperature difference.
Signal conditioning circuit:
The signals output from sensors often contain impurities such as electromagnetic interference and environmental noise. The signal conditioning circuit is like a "signal purification master", first using a Wheatstone bridge to amplify weak temperature difference signals by tens or even hundreds of times, enhancing signal strength; Then, through a low-pass filtering circuit, high-frequency interference signals are filtered out like a filter, retaining only the effective signals related to gas flow rate. After such careful refinement, the signal becomes pure and stable, laying the foundation for accurate calculation of gas flow rate.
Data processing and communication circuit:
The conditioned signal enters the data processing circuit and is commanded by a high-performance microprocessor. The microprocessor quickly and accurately converts the temperature difference signal into a gas mass flow rate value based on a preset algorithm. In the output stage, multiple communication protocols are supported, and 4-20mA analog signals are suitable for traditional industrial control systems. HART communication, relay alarm, Ethernet transmission, 4G material network platform, Modbus RTU digital communication protocol facilitate data exchange with intelligent instruments and upper computers, realizing remote monitoring and automation control, and enabling gas flow data to "run".
The thermal gas mass flowmeter produced by Angji Instrument has a circuit system that, with a high-precision measurement capability of ± 0.2%, controls gas flow fluctuations within a very small range, greatly improving the stability of chip manufacturing processes. In the field of natural gas metering, facing complex pressure and temperature changes in pipelines, the circuit system of the thermal gas mass flowmeter has the advantage of a wide range ratio (up to 100:1). Whether it is low flow pipeline leak detection or high flow trade settlement, it can accurately measure and help enterprises achieve efficient energy management.
The thermal gas mass flowmeter circuit, with its exquisite design and powerful functions, provides reliable gas flow measurement solutions for industrial production, environmental monitoring and other fields. Shanghai Angji Instrument Co., Ltd. has thermal circuits, including integrated plug-in, pipeline, and split wall mounted, and supports customization by phone.
Post time: Jun-05-2025