plc analog input modules which modules are composed mainly of

When deposited from the programming input to the user program memory and CPU system according to the function given by (system program memory compiler interpretation), translating into an internal PLC user program recognized by the users compiler.
Wang: plc analog input modules input state and input information from the input interface input, CPU will be credited to the work  industrial automation plc of the input image data memory or register. Then the data from the CPU and procedures together organically. The result is stored in the output image register or working data memory, and then output to the output interface, control external drive.
Composition: CPU by the controller, operator and register. These circuits are integrated on a single chip. CPU through the address bus, data bus and I / O interface circuit is connected. Semiconductor memory circuit with memory function. Into the system program memory and user memory.
System program memory to store the system procedures, including management procedures, monitoring programs, and to explain to the user program to do the compiler to compile process. Read only memory, ROM components. Manufacturers use the content can not be changed, power does not disappear.
User memory: User program memory is divided into data storage and work area. A random access memory (RAM) components. User. Power content disappears. Common efficient lithium batteries as a backup power plc intelligent controller  source, life is generally 3-5 years. Input / output interface
(1) plc analog input modules input interface: optocoupler consists of two LED and phototransistor extreme tube components.
LEDs: at the input of the optocoupler changes with an electrical signal, the light emitting diodes generates the same variation of the input signal is an optical signal.
Optical three tubes: In conducting the irradiation light signal, and the degree of conduction on the strength of the optical signal. In the linear operating region optocoupler output signal and the input signal has a linear relationship.
Input interface circuit works: When the switch is closed, plc analog input modules emitting diodes, and transistors under  plc controller manufacturer irradiation of light is turned on, the internal circuitry of the input signal. When the switch is off, the diode does not light, the transistor is not conducting. The input signal to the internal circuit. That is, through the input interface circuit of the external switching signal into the PLC can accept digital signals. (2) operation of a relay output circuit outputs the PLC: when the internal circuit outputs a digital signal, a current flows through the relay coil current, and the normally open contact is closed, the load is turned on to provide current and voltage. When the internal circuit outputs a digital signal 0, no current flows through the relay coil without current, and the normally open contacts open, the load current or voltage is off. That is, through the output interface circuit into the internal digital circuitry, or a signaling operation of the load does not operate.