The structure principle and common faults of transmitter

A transmitter is an electrical device used to convert one or more physical quantities (such as temperature, pressure, flow, etc.) into standard electrical signals (such as 4-20mA, 0-5V, etc.) for long-distance transmission, processing and control. It is usually used in industrial automation, process control, instrumentation and other fields, and is an indispensable and important part of modern industrial production processes.

The basic principle of the transmitter is to use the sensor to convert the measured physical quantity into an electrical signal, then process and amplify it through the circuit, and finally output a standard electrical signal. The main function of the transmitter is to convert the output signal of the sensor into a standard signal for long-distance transmission and processing. Since the output signal of the sensor is usually a weak electrical signal, it needs to be processed by amplification and filtering to meet the requirements of the standard signal. Therefore, the transmitter has important application value in the fields of industrial automation and process control.

1. Transmitter structure

A transmitter is an electronic instrument that converts various parameter signals into standard signal outputs. It consists of four parts: sensor, signal conditioning circuit, signal conversion circuit and output circuit. The sensor converts the measured physical quantity into an electrical signal, the signal conditioning circuit amplifies, filters, linearizes and processes the signal, the signal conversion circuit converts the signal into a standard electrical signal (such as 4-20mA or 0-10V), and the output circuit outputs the standard signal to the control system or display instrument.

2. Working Principle

The working principle of the transmitter is to convert the measured physical quantity into an electrical signal, and then convert the electrical signal into a standard signal output. For example, the sensor of the temperature transmitter is a thermistor or a thermocouple, which converts the temperature signal into an electrical signal; the signal conditioning circuit amplifies, filters, linearizes, etc. the signal; the signal conversion circuit converts the signal into a standard electrical signal (such as 4-20mA or 0-10V); the output circuit outputs the standard signal to the control system or display instrument.

3. Type

According to the different physical quantities being measured, transmitters can be divided into temperature transmitters, pressure transmitters, liquid level transmitters, flow transmitters, etc. According to the different types of output signals, transmitters can be divided into analog transmitters and digital transmitters. According to different installation methods, transmitters can be divided into insertion transmitters, flange transmitters, direct installation transmitters, etc.

4. Advantages of transmitter

1. High precision: The transmitter can convert the weak signal of the sensor into a high-precision electrical signal.

2. High reliability: The transmitter adopts advanced circuit design and process technology, and has high reliability and stability.

3. Strong adaptability: The transmitter can adapt to various environments and working conditions, such as high temperature, low temperature, high pressure, low pressure, etc.

4. Good flexibility: The transmitter can be configured and adjusted according to actual needs to adapt to various applications and requirements.

5. Easy to maintain: The transmitter has a simple structure and is easy to maintain, which can reduce maintenance costs and failure rates.

In addition to the above advantages, the transmitter has some shortcomings, such as:

1. High cost: The manufacturing cost of the transmitter is high, resulting in a relatively high price, which is not suitable for low-cost applications.

2. High technical requirements: The manufacture and application of transmitters require certain technical support and require high professional knowledge and skills.

3. Signal attenuation: Due to the long distance of signal transmission, signal attenuation and noise problems may occur, and corresponding measures need to be taken to compensate and adjust.

5. Common faults of transmitters

1. Power failure

Power failure is a common type of transmitter failure. Power failure mainly includes the following types:

(1) The power input voltage is too high or too low: When the transmitter is in use, if the power input voltage is too high or too low, it may cause the transmitter to work unstably or even fail to work properly.

Solution: First, check whether the power input voltage is normal; second, check whether the transmitter circuit board is damaged; finally, replace the power supply or replace the circuit board.

(2) Poor contact of the power supply circuit: Due to long-term use or improper operation, the power supply circuit of the transmitter may have poor contact problems.

Solution: First, check whether the power line is plugged in tightly; second, check whether the power line is damaged; finally, replace the power line.

(3) Short circuit of power supply line: A short circuit of power supply line will cause excessive current, thus causing damage to the transmitter.

Solution: Check whether the power circuit is short-circuited and eliminate the short-circuit fault.

2. Signal input failure

Signal input failure is also a common type of transmitter failure. Signal input failure mainly includes the following types:

(1) The signal input voltage is too high or too low: If the signal input voltage is too high or too low, it may cause the transmitter to work unstably or even fail to work properly.

Solution: First, check whether the signal input voltage is normal; second, check whether the transmitter circuit board is damaged; finally, replace the power supply or replace the circuit board.

(2) Poor contact of the signal input line: Due to long-term use or improper operation, the signal input line of the transmitter may have poor contact.

Solution: First, check whether the signal input line is plugged in tightly; second, check whether the signal input line is damaged; finally, replace the signal input line.

(3) Short circuit of the signal input line: A short circuit of the signal input line will cause excessive current, thus causing damage to the transmitter.

Solution: Check whether the signal input line is short-circuited and eliminate the short-circuit fault.

3. Output failure

Output failure is also a common type of transmitter failure. Output failures mainly include the following:

(1) Output voltage is too high or too low: Output voltage that is too high or too low may cause the transmitter to work unstably or even fail to work properly.

Solution: First, check whether the output voltage is normal; second, check whether the transmitter circuit board is damaged; finally, replace the power supply or replace the circuit board.

(2) Poor contact of the output line: Due to long-term use or improper operation, the output line of the transmitter may have poor contact.

Solution: First, check whether the output line is plugged in tightly; second, check whether the output line is damaged; finally, replace the output line.

(3) Output line short circuit: Output line short circuit will cause excessive current, thus causing damage to the transmitter.

Solution: Check whether the output line is short-circuited and eliminate the short-circuit fault.

4. Temperature failure

Temperature failure is mainly caused by the transmitter working in a high or low temperature environment for a long time, resulting in transmitter failure.

Solution: First, check whether the transmitter meets the working environment requirements; second, check whether the transmitter has a heat sink; finally, replace the heat sink or replace the transmitter.

5. Protection level failure

Protection level failure is mainly due to insufficient protection level of the transmitter, which causes the transmitter to be damaged during operation.

Solution: First, check whether the protection level of the transmitter meets the requirements of the working environment; second, replace the transmitter with a protection level that meets the requirements.

6. Other faults

In addition to the above common faults, the transmitter may also fail due to other reasons, such as circuit board damage, component aging, improper operation, etc.

Solution: Repair or replace according to the specific situation.

6. The development direction of transmitters

With the continuous advancement of science and technology, the development direction of transmitters is becoming more and more diversified. Among them, digitization and networking are one of the development trends of transmitters. Digitalization makes the signal processing of transmitters more accurate and the signal transmission more reliable; networking enables transmitters to achieve remote monitoring and control. In addition, energy conservation and environmental protection are also one of the development directions of transmitters. In the future, transmitters will be more energy-saving, environmentally friendly and intelligent.

In short, as an important industrial automation and process control equipment, transmitters have broad application prospects and market demand. With the continuous development and improvement of industrial automation, transmitters will play an increasingly important role and provide strong support for the modernization and efficiency of industrial production.