Plc is developed on the basis of logic control and sequence control. As a replacement for the heavy relay control cabinet and AC contactor control cabinet, plc realizes the automation and intelligence of industrial control. Sensor: It is a kind of front-end acquisition module, which converts the operating status of the field equipment, the pressure and liquid level signals into standard PLC control signals, and is used to provide PLC input control.
First, the sensor signal type:
1, analog signal: voltage signal or current signal! Used to provide analog input signals to PLCs and other devices. For example: pressure transmission signal, liquid level transmission signal, temperature transmission signal, differential pressure transmission signal, valve opening feedback signal, etc. are all analog signals. Supplement: The standard voltage signal is generally: 1v-5v, the standard current signal is generally: 4mA-20mA. Of course there are other non-standard voltage and current signals.
Digital signals are generally two states 0 and 1, which are on or off, and are used to provide on/off signals to PLCs and other devices.
Second, the corresponding PLC also has different input and output ports:
1, analog input port: receive analog signals such as sensors. 2, digital input port: receive digital signals such as sensors and other devices. 3, analog output port: used to control the analog output. For example: control valve opening. 4, digital output port: used to control the circuit on and off.
Third, industrial automation control: The sensor belongs to the front-end signal measurement equipment, PLC centralized processing control signals, as well as output actuators. 1, analog sensor and PLC analog input port, the corresponding output port can be analog signal can also be a digital control signal. 2, digital sensor and PLC digital input port connected, the corresponding output port is generally a digital signal.
Fourth, the sensor and PLC connected Note:
1. The sensor signal type needs to be the same as the PLC input port type. 2. There are many types of PLC. Generally PLC has digital input ports that can directly connect to digital signals. 3, if the PLC does not have an analog input port, it needs to be equipped with the same type of analog expansion module. General PLC will be equipped with 1-2 sets of analog ports.
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