The application of analog sensors is very wide, which can be seen in industry, agriculture, national defense construction, or in the fields of daily life, education, scientific research, etc. However, in the design and use of analog sensors, there is a problem of how to achieve the highest measurement accuracy. For different types of interference, there should be different anti-interference measures.
1. Anti-interference design of power supply system
The most serious hazard to the normal operation of analog PIR sensor is grid spike interference, which can be suppressed by a combination of hardware and software.
Suppress spike interference with hardware line
Suppress spike interference with software line
Suppress spikes with a "watchdog" technology combining of hardware and software
Implement group power supply
Apply noise filter
Apply isolation transformer
Apply high anti-interference performance of the power supply
2. Anti-interference design of signal transmission channel
Photoelectric coupling isolation measures
Long wire transmission of twisted-pair shielded wire
3. Elimination of local errors
In low-level measurement, the materials used (or constituted) in the signal path must be checked strictly. Solders, wires, and terminals in simple circuits may all generate actual thermoelectric potential. Because they often appear in pairs, it is an effective measure to keep these paired thermocouples at the same temperature. Therefore, some methods such as arranging heat shields and radiators along the isotherm, or separating high-power circuits and low-power circuits and other methods are all generally used.
4. Solutions to grounding problems
The commonly used voltage signal is 0V～10V, and the current signal is 0mA～20mA or 4mA～20mA, which are often used for long-distance transmission. The voltage signal is restricted by conditions such as the transmission distance during the transmission process, and the interference of the current signal during the transmission process has little influence on it, so the current signal should be used as much as possible. If there is a ground in the measurement loop, a potential difference will appear between the two ground points. This potential difference will have a great impact on the measurement results, so it should be avoided as much as possible.