In industrial control, in addition to digital signals, sometimes analog signals are used. There are three types of analog modules in Rockwell ABPLC : analog input modules, analog output modules, and analog input / output modules. (Ⅰ) Analog input module The analog input module is also called A / D module. It converts the continuous analog signal generated by the sensors on the spot into a digital quantity that the CPU of the PLC can receive. Generally, it is a 12-bit binary number. Module, the higher the resolution. (Ⅱ) Analog output module The analog output module is also called D / A module, which converts the digital quantity sent by the PLC's CPU to the analog output module into an analog quantity (voltage or current) that can be received by external equipment. The digital signal received by the analog output module is generally a 12-bit binary number. The module with more digital bits has higher resolution.
There are two types of interfaces:
(1) Peripheral communication interface
PLC is equipped with a variety of communication interfaces. ABPLC can communicate with programmers, printers, other PLCs, computers and other equipment through these communication interfaces. It can form a multi-machine system or connect into a network to achieve larger-scale control.
(2) Expansion interface
Used to connect I / O extension units and special function units. Through the expansion interface, you can expand the digital I / O points and increase the analog I / 0 terminals. You can also connect the intelligent unit to complete specific functions, making the configuration of the PLC more flexible to meet the needs of different control systems. The I / 0 expansion interface circuit uses two types of circuits: a parallel interface and a serial interface.