Study on Anti-interference of Heat Meter

A heat meter is a device for measuring heat. It can display the amount of heat used by heating users. Users can pay according to the amount of heat used to achieve the goal of metering and charging for heating users. Therefore, the use and promotion of this meter plays a huge role in saving energy, reforming the heating system, and improving the effective utilization rate of the energy of the heating system. However, the water quality in some parts of China is very poor, which has a destructive effect on the components of the heat meter. In this way, how to remove interference from the heating system is particularly important. For the source of interference and the propagation path of interference, the use of appropriate software and hardware anti-interference technology is an important means to improve the reliability of the single-chip microcomputer system.

1. Hardware anti-interference design

Reasonable hardware design can effectively suppress the source of interference and cut off the interference propagation channel. As long as the relevant parameters are reasonably set and selected, the hardware anti-interference technology can suppress most of the interference of the system.

1. Anti-interference design of system power supply

Since most heat meters are powered by batteries, the battery itself has high-frequency noise, which interferes with the normal operation of the system. Therefore, eliminating power supply interference is particularly important to ensure the reliable operation of the system. Two measures can be taken in the design of the heat meter: First, TI's TPS76350 voltage regulator chip can be used, which greatly improves the stability of the power supply; second, capacitors can be connected between the power supply and the ground of each IC chip on the circuit board for decoupling to eliminate high-frequency and low-frequency interference in the power supply.

2. Anti-interference design of turbine flowmeter

In order to ensure that the pulse signal output by the turbine sensor has sufficient sensitivity, the following aspects should be noted when configuring the signal transmission line: First, limit the maximum length of the signal line; second, the signal transmission line should use a shielded cable to prevent external inductive noise, the transmission line shield is grounded, and the transmission line cannot be close to strong point equipment. Third, optical coupling isolation is performed when the pulse signal enters the single-chip microcomputer.

2. Software anti-interference design

Through the reliability design of the software, the influence of interference on the operation of the heat meter system can be reduced, ensuring that the single-chip microcomputer in the heat meter can promptly detect errors in the program caused by interference, and restore the system to normal working state or alarm.

1. "Watchdog" technology In order to solve the problem of single-chip microcomputer being out of control due to interference, program monitoring technology, also known as "watchdog" technology, is usually used to make the program out of the "dead loop". During normal operation, once the WDT timing time is reached, a device reset will be generated, allowing the program to run again from the beginning.

2. Software digital filtering

Software digital filtering is to execute a program to reduce the amplitude of the interference signal by calculating the collected digital quantity and improve the signal-to-noise ratio. Common methods of software filtering include arithmetic mean filtering method, median filtering method, and anti-pulse interference average method.

3. Printed circuit board anti-interference design

Whether the circuit board design is reasonable has a great influence on the anti-interference ability of the system. Therefore, the design of the printed circuit board must follow some anti-interference design principles, and the following anti-interference measures should be taken in the design.

1. Processing of power lines and ground lines

In the design of the circuit board, the width of the power line and the ground line should be widened as much as possible. After the circuit board wiring is completed, the bottom and top layers are grounded, and the pins of the components on the circuit board that need to be grounded are connected with the copper layer, which can greatly improve the anti-interference performance of the system.

2. Analog circuit and digital circuit processing

In the design of the circuit board, the analog circuit and the digital circuit in the circuit should be distinguished. When making the PCB, the line width of the analog circuit should be appropriately larger than that of the digital circuit. The distribution of the analog ground and the digital ground of the AD converter should refer to its chip data and be laid out strictly according to its requirements.

3. Capacitor layout

The layout of the capacitor should place the decoupling capacitor, filter capacitor, and bypass capacitor around the corresponding components as much as possible. The routing, pin connection and wiring of the printed circuit board cause inductance, which will cause ripples and burrs on the power line. Placing a decoupling capacitor between the power supply and the ground can effectively filter out high-frequency ripples.

This article explains the anti-interference of the heat meter system from the aspects of hardware and software, which can significantly improve the anti-interference ability of the heat meter, enhance the practicality of the heat meter, and lay the foundation for the widespread application of the heat meter.

References:
[1] Qu Jianchang. Electromagnetic compatibility design of electronic equipment [M]. Beijing: Electronic Industry Press, 2002.
[2] Liu Guangbin, Liu Dong, Yao Zhicheng. Anti-interference technology for single-chip microcomputer system [M]. Beijing: People's Posts and Telecommunications Press, 2003.
[3] Liu Jie, Qi Lanfen. Simulation analysis of the influence of high-frequency interference on PCB electromagnetic compatibility and PCB optimization design [J]. Electronic Quality. 2006, (4): 83-88.
[4] Zhang Guoxiong, Jin Zhuanzhi. Measurement and control circuit [M]. Machinery Industry Press, 2003.
[5] Hongbin, Zhou Li, Chen Hongdong. Design of fault-tolerant technology of single-chip microcomputer embedded system software [J]. Industrial and Mining Automation. 2002, (l): 29-31. (end)