How to calibrate analog input module plc

plc analog input modules Some plc hardware calibration method, some use software calibration method, should prepare high-precision calibration of measuring instruments and stable input signal source, the number of samples to be taken as the average of the filtered larger value.
Hardware calibration method. S7-200 with EM235 analog input module, for example, analog input module has an offset adjustment potentiometer. Because only 0-20mA EM235 when the 4mA current applied to the input of a channel, read digital converted by programming software, adjust the offset potentiometer until the reading of 6,400.

Analog Input Module Features

plc analog input module features：
1, collecting multi-channel analog io module, industrial terminals, rail-mounted support.
2,485 interface input connected to the computer, and 485 provide optical isolation.
3, using MODBUS RTU communication protocol, enabling customers to unify PC management platform.
4, analog modules can be cascaded through 485 interface, easy system expansion.

Analog Input Module Definition

The analog input module is a remote site analog signal acquisition to the computer equipment, the use of RS-485 bus as a data communication line, provided to 485 analog functions, can simultaneously eight analog plc input module, and by RS-485 bus transfer to the computer. As a result of RS-485 interface as a communication interface, which is capable of transmitting a plurality of modules combination analog signal more large ones, and can be dispersed on a 485 line configuration, using the address code to distinguish, you can directly access the MODBUS RTU protocol configuration software.

digital output modules plc, which has several types, characteristics

igital output modules plc, which has several types, characteristics
According to different driving circuit, the digital output module can be divided into the following three categories:
High-power transistors and FET type - mainly used to drive DC loads.
Triac type - mainly used to drive an AC load.
Small relay type - used to drive AC or DC load, a contact signal outputplc digital input.
Switch if there is merit flexible output relay output AC and DC load large, slow to respond shortcomings
Advantages of fast reaction transistor output, shortcomings DC output, current, voltage is small.

Analog input and output module is good or bad

analog input module: Give a standard signal, look up the value of the mining right.
analog output module: output a value, using the following multi-meter.
If the range is consistent with the input connected to the output measured on the country, the bus portion of the output module to burn, so other channels can not be used is a continuous analog signal input and output, such as 4-20ma, 0-5v or 0 -10v, etc., than the column adjusting solenoid valve opening or used for any other use!

Function PLC communication modules

Function plc communication module, when the PLC communication port itself is not enough to use, because there may be more than one third-party PLC needs and communications instruments. Then you need to use the communication module plc, there are many types of communication module, a common serial module (RS232, RS485, RS422) and Ethernet communication module。

What is the definition of the analog input module

The analog input module is a remote site analog signal acquisition to the computer equipment, the use of RS-485 bus as a data communication line, provided to 485 analog functions, can simultaneously eight plc analog input module, and by RS-485 bus transfer to the computer. As a result of RS-485 interface as a communication interface, which is capable of transmitting a plurality of modules combination analog signal more large ones, and can be dispersed on a 485 line configuration, using the address code to distinguish, you can directly access the MODBUS RTU protocol configuration software.

plc modules in several categories

programmable logic control plc because of its high reliability, simple programming, versatility, small size, compact structure, easy installation and maintenance, etc., and in industrial control has been widely used. PLC modules are generally divided into the following categories:digital output module, analog input modules, analog output modules. In industrial control especially in the field of process control analog acquisition and control needs a relatively large amount, so the PLC analog input and output modules require more, and analog input and output modules are more expensive, increasing the analog input, output modules increases the cost and reduces the cost of the entire system, limit the application of PLC. This paper presents a simulation based on the amount of communication of input and output expansion module method seeks to solve this problem.

PLC input and output interfaces

The programmable controller is a digital computing operation of electronic systems, specialized applications in industrial environments. It uses memory can be programmed, used in instruction execution storage logical and sequential control, timing, counting and arithmetic operations such as operations and digital or analog input (I) and output (O) through the interface, to control various type of machine or production process.
Interface Plc modules and the electrical circuit is output through the input section (I / O) to complete. plc IO module integrates the PLC's I / O circuit, the input register reflecting the input signal, the output point to reflect the state of the output latch. Input module into the electric signal into a digital signal the PLC system, the opposite output module. I / O into the digital input (DI), switching output (DO), the analog input (AI), analog output (AO) modules.

— plc input modules, a method of low-cost expansion of output module

analog output plc, a method of low-cost expansion of output module programmable controller (hereinafter referred to as PLC) because of its high reliability, simple programming, versatility, small size, compact structure, easy installation and maintenance features, in the industrial control has been widely used. PLC modules are generally divided into the following categories: digital input modules, digital output modules, analog input modules, analog output plc. In industrial control especially in the field of process control analog acquisition and control needs a relatively large amount, so the PLC analog input and output modules require more, and analog input and output modules are more expensive, increasing the analog input, output module increases the cost and reduces the cost of the entire system, limit the application of PLC. This paper presents a method based on extended analog input and output modules of communication trying to solve this problem.

Programmable Logic Controller (PLC) software measures:

We have a strong self-test and protection.
① fault detection - software periodically to detect the external environment, such as a power failure, under voltage, battery voltage is too low and strong interference signals. So that timely treatment.
② Information Protection and Recovery - When sporadic fault condition occurs, does not destroy the plc industrial controller's internal information. Once the fault condition is removed, you can return to normal, continue the original program of work. Therefore, profibus module plc when the fault condition is detected, immediately put the current state stored in the memory, software with the memory is closed to the memory of any action to prevent the storage of information is obliterated.
③ Set the Watchdog WDT (Watchdog) - If the program execution time per cycle than the WDT specified time, indicating the program into an infinite loop, call the police.
④ strengthen inspection and verification procedures - once the program is wrong, call the police, and stops executing.
⑤ the program and dynamic data backup battery - after a power outage, use battery-powered back-up, and information about the status will not be lost.
PLC factory pilot project, there is an immunity test. It is required to withstand the amplitude of 1000V, the rise time 1nS, a pulse width of the pulse 1μS of interference. In general, the average time between failures of up to hundreds of thousands - tens of millions of hours; the system can be made up to 4 to 50,000 hours or longer.

Medium programmable control system

Medium plc industrial controller may provide the functionality and flexibility you need, do not have that kind of overhead systems, it is the perfect solution for medium-sized application projects. Select rack-based, modular package design standards and safety certification from the controller. Typical applications include complex machine control, batch processing and building automation.

PLC current loop transmission

Application of the current control loop is started in the early 1900s teletype, the earliest use of the 0-60mA loops and later changed to 0-20mA loop, programmable logical controllers system is the first to use the 4-20mA loop.
4-20mA current loop has many advantages. Need to be carefully calculated in the traditional discrete component designs, and compared with the current integrated 4-20mAIC, circuit take up a lot of space.
Any current values ​​measured are representative of certain information. Practical applications, 4-20mA current loop in 0mA to 24mA current range. But 0mA to 4mA and 20mA to 24mA current range for diagnostics and system calibration. Due to lower than 4mA and above 20mA are used for diagnostics, it is believed readings between 0mA and 4mA could indicate a broken wire in the system. Similarly, between 20mA and 24mA between readings can indicate a potential short circuit occurred in the system.
Plus 4-20mA communications Highway Addressable Remote Sensor, which is backward compatible with 4-20mA instrumentation. In HART system uses microprocessor-based intelligent integration of field devices enables two-way communication. The HART protocol capable of carrying additional digital information on the same line 4-20mA analog current signal for process control.
plc analog input output module functions can be divided into several functional groups. Many plc controller manufacturer vendors will integrate these functions as separate modules, each module with features vary with the specific application. Many modules have multiple functions, it can interface with a variety of sensors. However, for specific applications will design special modules or expansion modules, such as in most cases: resistance temperature detector (RTD), sensor, or thermocouple sensor. In general, all modules have the same core functions: analog input, analog output, distributed control (eg fieldbus), interface, digital input and output (I / O), CPU and power supply.

Nanda programmable logic controller suppliers

PLC control system and electrical control system distinguish the

PLC control system compared with the electrical control system, there are many similarities, there are many different. The difference is mainly in the following areas:
1) Judging from the control method, the electrical control system control logic hardware wiring, mechanical relay contacts using series or parallel, etc. combined into a control logic connections are many and complex, bulky, power consumption, system configuration, the I would like to change or add functionality more difficult. In addition, a limited number of contacts of the relay, the electrical control system flexibility and scalability is very limited. The PLC technology uses a computer, which controls the way the program logic is stored in memory, to change the control logic simply by changing the program, which is easy to change or increase the system functionality. System wiring small, small size, low power consumption, and PLC-called "soft-relay" is essentially a state of the memory cells, so "soft relay," the number of contacts is unlimited flexibility and scalability plc controller manufacturer system good .
2) From the work point of view, in the relay control circuit, when the power is turned on, the circuit is subject to all relays are in the state, that is, the pull of the relays are energized at the same time, should not be subject to some kind of pull-in relay conditions can not pull, this way of working called parallel work. The plc ethernet module user program is executed cyclically according to a certain order, so that each soft relays are in a cyclical scan cycle turned in by the same conditionality order each relay operation depends on the program scan order, this way of working is called Serial work.
3) Judging from the speed control, relay control system relies on mechanical contact action to achieve control, low operating frequency, mechanical contacts will appear jitter. The PLC to achieve control of program instructions by controlling the semiconductor circuit, high speed, program instruction execution time in microseconds level, and will not appear contact bounce problem.
4) Judging from the timing and the counting control, electrical control system uses the operating time of the relay delay the time control, time delay relay susceptible to ambient temperature and temperature changes, the timing accuracy is not high. The PLC semiconductor integrated circuit as a timer, a clock pulse is generated by a crystal oscillator, high precision, wide time range, the user can set the timer value in the program as needed to facilitate changes, affected by the environment, and the PLC have counted functions, and electrical control systems generally do not have the counting function.
5) From the point of view of reliability and maintainability, since the electrical control system uses a large number of mechanical contact which mechanical wear, arc burns, short-lived, multi-link system, the reliability and maintainability of the more difference. The PLC large number of switching operation performed by non-contact semiconductor circuit to complete its long life, high reliability, PLC also has a self-diagnostic function, able to detect its own fault, displayed to the operator at any time, and can dynamically monitor control the implementation of the program for on-site commissioning and maintenance more convenient.

The sudden emergence of micro programmable logic controller

Traditional micro plc temperature control module is generally 8 to 64 digital I / O, 1 ~ 4 points analog I / O, small size, can be installed directly in the machine. But now the miniature programmable controller in addition to the above functions, can be compared with the already large programmable controllers on the network functions and man-machine interface functions, this type of micro programmable logic controller manufacturer is currently the fastest fast.

Penetration programmable controller

programmable logical controllers is to adapt the plant control systems and enterprise information management systems increasingly combine trends and adapt to the control level make between different brands of programmable logic controllers, PLC and Distribution effective exchange of data between the requirements of control system. In fact, the realization of multi-tasking system, improve network capabilities, software integration makes the development of information technology, very easy to integrate with a programmable logic controller system.

Programmable Logic Controller Development in China and Countermeasures

The current development of the programmable logic controller (plc) suppliers of the main faces of the three problems. In the rapid development of the international situation, programmable logic controller, with independent intellectual property rights, China has no one on the technical level, can compete internationally programmable controller products, mainly due to the foundation of the whole industry is still There are some gaps, such as aspects of chip manufacturing, mold processing limitation of our development. The second is, in fact, also a question of economic competition competitive level. Now 95% of the domestic market occupied by foreign PLC Programmable Logic Controller, medium and large programmable controller, almost all dominated by several major foreign companies, as China continues to expand the use of field programmable logic controller , the market is growing, however, several major foreign companies almost every year for the market introduction of new products, once people use a new product, they will gradually increase the market price, not our own independent intellectual property rights In economic competition can only be passive. Third, the level of the market order, with the deepening of China's reform and opening up, especially after joining the WTO, China's huge market share greatly attracted foreign companies, they open up the market a wide range of methods are based on an agency sales channels, each company's distributors, system integrators will have dozens, even hundreds of many, resulting in intense competition our distributors, system integrators among these disorderly competition is international large companies divide and rule, get a stable high profits to create the conditions.

Application of Programmable Controller (PLC)

Currently, PLC has been widely applied at home and abroad in metallurgy, petroleum, chemicals, building materials, machinery manufacturing, electric power, automobile, light industry, environmental protection and cultural entertainment and other industries, with the continuous improvement PLC cost performance, its applications continue expand. From the application type, application plc IO module can be broadly summarized as follows:
1. logic control switch
Using PLC basic logic operations, timing, counting and other functions to implement logic control, can replace traditional relay control for stand-alone control, multi-cluster control, automatic production line control, such as: machine tools, injection molding machines, printing machinery, assembly lines , plating lines and elevator control. This is the most basic application PLC, PLC is the most widely used applications.
2. Motion Control
Most PLC has to drag a stepper motor or servo motor single or multi-axis position control module. This feature is widely used in a variety of mechanical equipment, such as machine tools, assembly machinery, robots and other motion control.
3. Process Control
Large and medium-sized plc cpu modules has multi-channel analog I / O modules and PID control functions, and some small-scale PLC also has analog input and output. So PLC enables analog control, and has PID control function PLC may constitute a closed-loop control for process control. This feature has been widely used in boilers, reactors, water, wine, and closed-loop position control and speed control and so on.
4. Data Processing
Modern PLC have math, data transfer, conversion, and table sorting and other functions, can collect, analyze and process the data, while the data via the communication interface is transmitted to other intelligent devices, such as computer numerical control (CNC ) device for processing.
The communication network
PLC communications, including communications, programmable logical controllers systems and general-purpose computer PLC and PLC, PLC and host computer, PLC and other intelligent devices can directly or through the communication processing unit, a conversion unit connected to the communication network to achieve the exchange of information and may constitute "centralized management, decentralized control," the multi-level distributed control system to meet the needs of factory automation (FA) systems development.

Data communication between analog modules

Buffer register (BFM) allocation

FX series PLC basic unit and FX - 4AD, FX - 2da etc. analog module between data communication is performed by the from and to instructions, communication modules plc ,from is basic unit reads data from the FX -- 4AD, FX - 2da instruction, the TOS are from the basic unit writes the data to the FX -- 4AD, FX - 2da instruction. Actually read and write operations are FX - FX, 2DA - 4AD buffer register BFM.

This buffer register consists of 16 registers of 32 bits, plc communication modules ,numbered #31 1 BFM#0.