What is the difference and connection between the transmitter and the sensor? -Huaqiang Electronic Network

1

What is the difference and connection between the transmitter and the sensor?

A sensor is a general term for a device or system that can detect and convert physical quantities into an available output signal according to a specific rule.

, Usually composed of sensitive components and conversion components. When the output of the sensor is a specified standard signal, it is called a transmitter.

Sensor

SENSOR:

National standard GB7665-87 defines a sensor as: "A device or system capable of sensing a specified measurement and converting it into a usable signal according to a certain rule, typically consisting of a sensitive component and a conversion component." It is a detecting device that senses the measured information and transforms it into an electrical signal or another required form of output according to a certain law, satisfying the needs for transmission, storage, display, recording, and control. It is the first step in achieving automatic detection and automatic control.

Transmitter

Mitter

) :

When the signal converter is integrated with the sensor, it is called a transmitter. According to the definition from the "China Encyclopedia," a transmitter outputs a sensor signal in a standard format.

According to national standards, a device that produces a specified standard signal is called a transmitter. The concept of a transmitter refers to an instrument that converts a non-standard electrical signal into a standard one, while a sensor converts physical signals like temperature, pressure, or level into electrical signals.

Sensors and transmitters are key components in thermal instrumentation. Sensors convert non-electrical physical quantities such as temperature, pressure, liquid level, material, and gas characteristics into electrical signals or directly send them to the transmitter. The transmitter then amplifies the weak electrical signal collected by the sensor to transmit or activate control elements. In some cases, it also acts as a signal source that converts non-electrical inputs into electrical signals for remote measurement and control. Analog signals can be converted into digital ones as needed. Together, sensors and transmitters form an automatically controlled monitoring signal source. Different physical quantities require different sensors and corresponding transmitters. Some transmitters do not convert physical quantities into electrical signals, such as a boiler water level gauge.

"

Differential pressure transmitter"

” He sends the lower water in the liquid level sensor and the condensed water of the upper steam to the two sides of the bellows of the transmitter through the instrument tube. The differential pressure on both sides of the bellows drives the mechanical amplifying device to indicate the water level with a pointer. A kind of remote instrument. Of course, it is also possible to convert the electrical analog quantity into a digital quantity. The above just conceptually illustrates the difference between a sensor and a transmitter.

2

,

sensor and transmitter output signals

1

Current signal:

4--20mA 0--20mA

2

,

Voltage signal:

0--5V

,

1--5V

Wait

mV

signal

3

,

Resistance signal.

4

,

Pulse signal.

The above signals can be changed to standard by the transmission module or circuit board.

4--20mA

signal. At the same time, the name is not called a sensor.

3

What is the transmitter's two-wire and four-wire signal transmission methods?

?

In the two-wire transmission mode, the power supply, load resistance, and transmitter are connected in series, meaning that the two wires simultaneously transmit the power and output current signals required by the transmitter. Currently, most of the transmitters are two-wire transmitters. In the four-wire system, the power supply and load resistance are separately connected to the transmitter, meaning that the power supply and the transmitter output signals are transmitted via two separate wires.

The two-wire system means that the field transmitter is connected to the control room meter using only two wires, which serve as both the power line and the signal line.

4

,

primary instrument and secondary instrument

From the professional interpretation, the secondary instrument accepts signals from the transmitter, converter, and sensor (including thermocouples, thermal resistance). It is a meter that sends an electrical or pneumatic signal and indicates the magnitude of the process parameter being tested. For example, the physical display, temperature control, etc.

One meter is a signal acquisition conversion (various transmitters, temperature element, signal acquisition equipment). The secondary meter is to display the alarm adjustment (the panel display alarm instrument), the input of the decentralized control system, and the input of the distributed control system.

5

,

the difference between transformers and transformers

Transformers and transformers work the same way, all use the principle of electromagnetic induction to operate. The role of the transformer is to convert one level of voltage into another level of the same frequency. It can only achieve voltage conversion, not power conversion. Transformers are divided into voltage transformers and current transformers. The role of the voltage transformer is to supply the measuring instrument, relay voltage, thus correctly reflecting the various operating conditions of an electrical system. Measuring instruments, secondary electrical systems such as relays are isolated from the primary electrical system to ensure the safety of personnel and secondary equipment. Converting the high voltage of an electrical system to a low voltage value that agrees with the standard (100 Volt, 100/1.732 Volt, 100/3 Volt). The role of the power transformer is basically the same as that of the voltage transformer. The difference is that the current transformer is to transform the high current of the primary electrical system into a standard 5 A or 1 A, providing power for electrical appliances, current coil of measuring instruments. The transformer itself has no electricity; it can sense the energy after the other coil is energized to generate the magnetic field. And the transformer is used to change the voltage, such as 10,000 volts passed through the transformer and turned into 220 volts, which is a tool to change the voltage, you can step down, of course, you can also rise! Mutual transformer is a kind of transformer. Used in the actual circuit for blocking and impedance transformation. Used on input and output interfaces in power and electronic circuits.

Industrial control system

Industrial control system is an automation technology for measuring and controlling industrial production processes and their electromechanical equipment and process equipment. (Including automatic measuring instruments and control devices) The general term includes computer systems (including software and hardware devices) for industrial control, sensors and transmitters for information acquisition, and instrumentation and actuators for command execution. Among them, the computer system is the core of the industrial control system, including the programmable controller (PLC), industry PC Machine, distributed control system (DCS), embedded computer, fieldbus control system (FCS), mechanical and electrical equipment numerical control system (CNC, FMS, CAM), etc.

(1) programmable control

According to the International Electrotechnical Commission (IEC) definition: programmable controller (PLC) is an electronic system for digital computing operations designed for applications in industrial environments. It uses a programmable memory for storing instructions that perform operations such as logic operations, sequence control, timing, counting, and arithmetic operations, and controls various types through digital, analog inputs and outputs. Mechanical or production process. The programmable controller and its related equipment should be designed in such a way that it is easy to integrate with the industrial control system and easily expand its functions.

PLC has the characteristics of strong versatility, convenient use, wide adaptability, high reliability, strong anti-interference ability and simple programming. Its position in industrial automation control, especially sequential control, cannot be replaced in the foreseeable future. Structurally, PLC is divided into fixed and combined (modular) two. Fixed PLC include CPU board, I/O Boards, display panels, memory blocks, power supplies, etc. These elements are combined into a non-detachable unit. Modular PLC include CPU Module, I/O Modules, memory, power modules, backplanes, or racks, these modules can be configured in accordance with certain rules.

Due to the complexity and difficulty of controlling content, make PLC towards integration, PLC versus PC integrated, PLC versus DCS integrated, PLC versus PID Integration, etc., and strengthen communication capabilities and networking, especially PC The growth rate of the base-based control products is the fastest. PLC versus PC integrated, Coming soon computer, PLC And the operator - Machine interface combined, Make PLC Can use computer-rich software resources, And the computer can PLC The module interacts with the data. Take PC Machine-based control makes it easy to program and maintain user benefits, Open architecture provides flexibility, Ultimately reduce costs and increase productivity.

(2) industry PC machine

industry PC machine( IPC ) is suitable for industrial harsh environments. PC The machine is equipped with various process input and output interface boards to form an industrial computer. Appeared again in recent years PCI Bus industrial computer.

As a computer with special performance, industrial computer (IPC) It is capable of stable operation for a long time in a harsh external environment, resulting in the special requirements of high adaptability and high reliability of the process control and manufacturing automation in the traditional industry. initial, IPC Mainly used in professional industrial control field. due to IPC With anti-harsh environment, good structural expansion performance, wide voltage range, various I/O The equipment is fully equipped and it is normal PC The full compatibility of the software and many other advantages make its application more extensive than ordinary PC .

In the past few years, after the test and selection of the market, PC Bus industrial computer has gradually become the mainstream of the development of the industrial computer market. It has software and hardware bus standards and universal PC Fully compatible, high performance and price ratio, large output, high degree of popularity, familiarity and recognition of the majority of technical personnel and many other technical performance and market advantages, has become synonymous with industrial computer in the industry, PC Bus has also become an important bus type in the field of industrial computer, representing the development direction and future trend of industrial computer technology.

At present, the application field of industrial computer in China is expanding, and the proportion of traditional industrial field application and process control applications has dropped to 15% And communications and telecommunications applications are rapidly rising to twenty two%, Electricity is 10%, traffic 7%, Video Surveillance 10%, military 12%, The internet 6%, finance, gaming 6%, other 12%. Simultaneously DVR, inquiry machine, machine, integrated instrument, etc. IPC Embedded applications are rapidly emerging and occupying IPC The increasing market share of the application market has also replaced some of the common PC Occupied market area. The next few years, PC Bus industrial computer and industrial automation products will increase exponentially. The application field of industrial computer will further develop in depth, and the industrial computer will enter a stable period of sustained high-speed development.

(3) Distributed control system

Distributed control system (DCS) Also known as the distributed control system. Distributed control system is from each of the networks that make up the control system I/O Subsystem to each I/O Each of the subsystems I/O The composition of the points adopts a completely modular structure without exception. And each one I/O Points are independent and do not interfere with each other. Every I/O Conditioning, A/D Both the conversion and monitoring control types are configurable and independent of each other at the height point. From the physical structure, each one I/O Points can be based on the scene I/O Choose different types of signals I/O Module. It is designed from the hardware structure to ensure that when any fault or damage occurs, it will not affect the normal operation of any other equipment in the system. I/O Module replacement allows the entire system to operate properly. Because this replacement does not involve other I/O Point, of course, does not need to shut down the entire system or partial system, which affects the normal operation of any part of the system. Currently, this design has been seen as a model for reliability design in distributed control systems.

From the perspective of system structure, each one I/O The subsystem is the smallest computer that constitutes the distributed control system (Also known as a smart controller or I/O Controller), I/O Mount, I/O Module and communication interface unit. It has all the necessary elements to exercise control and monitoring intelligence: including CPU, Memory, I/O Control functions, communication capabilities, network support, high-level language programming capabilities, ladder logic language capabilities, scalability and online data modification capabilities. I/O Controller and I/O Passing between modules I/O The mounting brackets are connected, I/O The module is connected to the site. Per subsystem I/O Processing power depends on the design level of the controller.

intelligent I/O Modules are self-contained and freely configurable, avoiding the emergence of other types of control systems "Superfluous I/O Point" The ills, in the event of a breakdown, will not be repaired because of a problem I/O Points must be combined with others I/O The point is also removed, and there is a higher performance-price ratio in the retention of spare parts.

Controller and controller (Between subsystems and subsystems) And between the engineer workstation and the subsystem, a highly reliable, high-speed, easy-to-configure communication network can be used, such as Ethernet, Arcnet, Modbus, OptoMux Wait. Can also use the current popular field bus, such as Lonworks, DeviceNet, Profibus Wait.

(4) Embedded computer

Embedded computer platforms are widely used in military, industrial control, electronic medical equipment and communications. The target market generally has the following characteristics: reliability requirements are higher than requirements for computing power. Typical applications include elevators and intelligent traffic signal control. , electronic medical equipment, electrical equipment monitoring, banking and ATM Machine monitoring, etc.; requires minimum development risk and minimum development cycle; requires strong upgrade capability; requires long-term maintenance or technical support.

As a kind of knowledge cross-over product, the embedded computer platform has different customer needs in different application fields. A good embedded computer must have an international standard bus structure, a wealth of highly reliable hardware modules, and a rugged embedded BIOS It is compatible with good software and can support various real-time operating systems with small size and low power consumption. To quickly build a highly reliable embedded control system, it is especially important to establish a deep and long-term partnership between embedded computer platform manufacturers and customers. With the rapid development of global information technology, people's requirements for the function and reliability of embedded systems are getting higher and higher, and they are constantly moving towards modularization. As embedded microprocessor functions become more and more powerful, the software and hardware of the products become more and more complex, and the various processors produced by different manufacturers are not compatible, and the vast number of embedded application system manufacturers face greater challenges. If you choose the processor directly from the beginning, you will not only face the risk of development failure, but also the development speed is difficult to meet the market demand. The modular embedded computer platform not only provides a complete application development platform standardized by software and hardware interfaces, but also can be tailored to the specific requirements of customers, so for embedded application system manufacturers who are looking for a shorter time to market, Modular solutions will undoubtedly be favored by them more and more.

(5) Fieldbus control system (FCS)

Fieldbus technology integrates digital communication technology, computer technology, automatic control technology, network technology and smart instrumentation to form a fully distributed, fully digital, intelligent, bidirectional, interconnected, multivariable, multi-contact communication. And the control system is a digital, two-way transmission, multi-branch communication network connecting intelligent field devices and automation systems, based on smart meters. Smart meters dispersed in various industrial sites are connected by digital fieldbus and together with controllers and monitors in the control room form a fieldbus control system (Fieldbus Control System, FCS).

By following certain international standards, fieldbus products from different vendors can be integrated into the same set. FCS Medium, interchangeable and interoperable. FCS Put the tradition DCS The control function is further decentralized to the on-site intelligent instrument, and the functions of data acquisition, data processing, control calculation and data output are completed by the on-site intelligent instrument. The data of the field instrument (including the collected data and the diagnostic data) is transmitted to the control device of the control room through the field bus. The control device of the control room is used to monitor the running status of each field instrument, and save the data uploaded by each smart meter, and complete at the same time. Advanced control features that cannot be completed with a small number of field instruments.

FCS The key to the technology is smart meter technology and fieldbus technology. The smart meter not only has the advantages of high precision, self-diagnosis, but also has control functions, which will replace the traditional 4-20mA Analog meter. The fieldbus connected to the field smart meter is an open, digital, multi-contact bidirectional transmission serial data path, which is a combination of computer technology, automatic control technology and communication technology. Combine PC The rich hardware and software resources not only overcome the shortcomings of the traditional control system, but also greatly improve the flexibility and efficiency of the control system, form a new control system, create a new era of automatic control, and become the inevitable development of automatic control. trend.

The output of the controller is added to the controlled system through the output interface and the actuator. The controlled quantity of the control system is sent to the controller through the input interface through the sensor and the transmitter, thus completing a normal operation control operation.

For example, the first input point is connected to the motor start signal, the second one is connected to the stop signal, the first output point is connected to the intermediate relay, and then the contactor is controlled to control the motor operation. When the start button is pressed, the first input is lit, the program detects that there is a start signal input, executes the program, the first output point moves, the intermediate relay pulls in, the contactor moves, and the motor works. When there is a signal at the second input point, the stop signal is pressed, the program moves, and the stop operation is performed. The first output point is off, the intermediate relay is de-energized, the contactor stops working, and the motor stops working.