Causes and consequences of interference in four common single-chip measurement and control systems

There are four main reasons for interference to the microcontroller measurement and control system:

1. Grid interference

Most single-chip microcomputer control systems use AC power supply. The quality of the power grid directly affects whether the system can work properly. Power grid interference mainly includes surge voltage and electromagnetic interference. When high-power electrical equipment in industrial sites starts or stops, it will cause surge voltages of hundreds of volts or even thousands of volts accompanied by spark interference. In addition, when the power grid frequency is unstable or the power grid voltage is undervoltage or overvoltage for a long time, it will also affect the performance indicators.

2. Transmission line interference

Transmission line interference is interference formed on the input and output lines, also known as channel interference. A large single-chip microcomputer measurement and control system may require hundreds or even thousands of temperature sensors, with thousands of input and output lines, and their lengths can reach tens to hundreds of meters. This can easily introduce interference from industrial sites into the system. In mild cases, errors will occur, and in severe cases, useful signals can be completely submerged, making it impossible to measure or even damaging the single-chip microcomputer measurement and control system. When the signal is close to the 220V AC power line, 50HZ interference will also be introduced.

3. Space electromagnetic wave interference

The energy of electromagnetic interference is transmitted in the air in the form of electromagnetic filters. It includes electromagnetic waves radiated by celestial bodies such as the sun, electromagnetic waves emitted by radio, television and various wireless communication equipment, and electromagnetic interference generated by household appliances such as air conditioners, fluorescent lamps, and microwave ovens. Electromagnetic waves will not only seriously interfere with the normal operation of electronic equipment, causing program loss of control and control failure, but also directly endanger human health and even cause permanent damage. This has attracted great attention from the electronics industry at home and abroad. For this reason, my country formulated the "Electromagnetic Radiation Protection Regulations" as early as 1987, and promulgated the "Electromagnetic Radiation Environmental Protection Management Measures" in 1998 to strengthen the unified management of the national electromagnetic radiation pollution environment.

4. Internal interference

It should not be ignored that any electronic device in operation is itself a source of interference. The internal interference of the single-chip microcomputer measurement and control system is also divided into two categories: series mode interference and common mode interference. The internal interference signals include spark discharge interference, self-excited oscillation, peak-like interference, noise voltage, etc. generated by electromagnetic relays.