Data acquisition module application in the PLC control system

Keywords:
PLC (Programmable logic Controller)
Analog to Digital Converter, RS-485 serial communications, data acquisition, I / O remote monitoring
 
In the industrial production process, there are many continuous variables, such as temperature, pressure, flow, level and speed all are analog. To make the programmable controller to handle analog signal, need achieve the A / D or D / A conversion. PLC manufacturers are supporting the production of A / D and D / A converter module, the programmable controller for analog control. And in the actual working environment, the analog current or voltage signal output of the PLC systems are often weak (mV or mA level), but generally with a load capacity. Directly used to monitor the remote execution of equipment, often because of long-distance transmission can degrade the signal distortion, and sometimes other external signal interference caused by signal error, affecting the normal operation of the entire system. This requires that the thermal resistance, thermocouple temperature signals and the current/voltage signals collected by the digital output port via the RS485 serial interface using a standard communication protocol data sent to the PLC.

Product Overview:                                              
 WJ21 series products realize the signal acquisition between sensor and host, to measure analog signals. WJ21 products can be applied to RS-232/485 bus industrial automation control system,4-20mA / 0-5V signal measurement, monitoring and control,0-75mV ,0-100mV and other small-signal measurement and signal isolation and long-term industrial  transmission and so on.
Products include power supply isolation, signal isolation, linearization, A/D conversion and RS-485 serial communication. Each serial interface can connect up to 255 pieces    WJ21 Series modules, communication using ASCII code or MODBUS RTU communication protocol, and its instruction set compatible with the ADAM modules, baud rate can been set by the code, with other manufacturers control module hang in the same RS-485 bus for easy programming.

Conclusion:
In short, the A/D converter and D/A converter to play an important role in the PLC control system. PLC applications continue to broaden the analog acquisition module ADC, DAC will have a greater development of the variety of products will be richer, more complete specifications, will be better adapted to the needs of a variety of industrial control applications as automation control an important part, will play an increasing role in the field of industrial control.

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