The current situation and future development trend of pressure transmitters at home and abroad

1.High-precision pressure output with an accuracy of . 2.

Digital output, direct reading of pressure value, reading resolution is less than. 3.It also provides a high-precision temperature digital output with an accuracy of 1.

4.It supports RS485 twisted pair network and can carry 32 LDD series transmitters. When there are more than 32, RS485 repeaters are required.

5.Low power consumption, quiescent current less than 6mA, wide DC voltage power supply Fanchai dust circumference: 12V 24V.

Suitable for battery or solar powered. 6.Switch between nine commonly used pressure units MPA, KPA, PSI, KG CM2, MH2O, Bar, MMHG, ATM, and USR.

The error caused by switching between pressure units is less than that. 7.The tare function shifts the digital output to 0 at any pressure point without affecting the output sensitivity of LDD products.

8.Scale factor function, you can set the scale factor between so that the current digital output is equal to the product of the current pressure value and the scale factor. When measuring the level, the scale factor can be set to equal the reciprocal of the specific gravity of the liquid, so that the digital output is directly equal to the current level height.

9.Embedded DSP, digital processing of LDD, digital compensation by piecewise polynomial fitting method, including pressure nonlinear compensation in the whole temperature range, zero and sensitivity compensation, etc. Half-duplex serial asynchronous digital communication interface with 7 communication rates to choose from, namely (bps):

1200，2400，4800，9600，19200，38400，57600。The working protocol of the digital communication interface is: 1 bit to start Zheng Qi bit, 8 bits to data bits, and 1 bit to stop.

The transmission distance is 1200 meters. The command return delay time is about 10ms. 11.

The address of each LDD can be changed. The address range of the ASCII code command is 0 9 of the ASCII character, or a z, or a z. Command format and binary command format, the two formats can be used at the same time, which is convenient for users to use and secondary development 13

Dedicated zero and sensitivity (full scale) correction commands facilitate calibration of LDD series products. 14.The pressure reading refresh cycle is 100 ms (sampling frequency 10 times).

The initial power-up settling period is 2 seconds.

In general, a pressure transmitter is mainly composed of three parts: a load cell sensor (also known as a pressure sensor), a measurement circuit and a process connection. It can convert the physical pressure parameters such as gas and liquid felt by the load cell sensor into standard electrical signals (such as 4 20madc, etc.), and supply secondary instruments such as indicating alarms, recorders, and regulators for measurement, indication and process adjustment.

Shengen Automation.

Intelligent development of pressure transmitter controller:

2) Compared with the ordinary pressure transmitter controller, the intelligent transmitter has the characteristics of high precision, good stability, high reliability, wide measurement range and large range ratio, etc., and the intelligent transmitter has a perfect self-diagnosis function, and adopts a lot of high-tech, sensing technology, microelectronic digital processing technology, etc.

3) Simplify the system components; The intelligent differential pressure transmitter only needs to obtain the output signal with the square root relationship of the input differential pressure signal through simple setting, so it can eliminate the need to use the square link of differential pressure flowmeter and simplify the composition of the measurement and control system.

4) Various parameters can be displayed on site; With a simple setting of the instrument, the built-in LCD module of the intelligent pressure transmitter controller can display a variety of different data.

5) Reduce the number of instrument spare parts; The intelligent pressure transmitter controller is used to have a large range ratio. And it has the ability of self-setting and self-calibration, and it is only necessary to modify the small-range differential pressure value and large-range differential pressure value in the control room through the intelligent terminal to complete the same purpose. It avoids the disassembly, assembly and calibration of the conventional pressure transmitter controller, reduces the maintenance of the instrument worker, and reduces the number of spare parts.

Mechanical to electronic transformation.

Analog signals are transformed into digital signals.

Shift from individual control to complete system integration!

Pressure transmitters are an important component used in many industrial equipment to control industrial processes and pressure changes. Pressure transmitters are used to measure the level, density and pressure of liquids, gases or vapors, and then convert the pressure signal into a 4 20mdc signal output. Pressure transmitters are divided into capacitive pressure transmitters and diffusion silicon pressure transmitters, ceramic pressure transmitters, strain gauge pressure transmitters, etc.

The pressure transmitter is a field instrument that is in direct contact with the measured medium, and often works in high temperature and low temperature corrosion, vibration, impact and other environments. It is widely used in pressure measurement and on-site control in petroleum, chemical, electric power, steel, light industry and other industries.

The development of pressure transmitters has gone through four stages:

1. In the early days, pressure transmitters used the working principle of large displacement, such as mercury float differential pressure gauge and diaphragm box differential pressure transmitter that were mass-produced, which had low accuracy and were bulky.

In the 50s of the century, there was a force balance differential pressure transmitter with slightly higher precision, but the feedback force is small, the structure is complex, and the reliability, stability and vibration resistance are poor.

In the middle of the decade, with the emergence of new processes, new materials and new technologies, especially the rapid development of electronic technology, displacement transmitters with small size and simple structure appeared.

With the rapid development of science and technology, these transmitters have high measurement accuracy and are gradually developing towards intelligence, and digital signal transmission is more conducive to data acquisition.

So far, there are different types of pressure transmitters, such as capacitive transmitters, diffusion silicon piezoresistive transmitters, differential inductive transmitters and ceramic capacitive transmitters.

In the 90s of the 20th century, fieldbus technology rose rapidly, and industrial process control systems gradually developed in the direction of fieldbus control systems with two-way communication and intelligent instrument control. The result is a new generation of intelligent pressure transmitters. Their main features are as follows.

1. Self-compensation functions such as nonlinearity, temperature error, response time, noise and cross-induction, etc.

2. The self-diagnosis function is such as self-checking when the power is turned on, and the operation check is realized in the work.

3. The function of two-way communication between the microprocessor and the basic sensor constitutes a closed-loop working system.

4. Information storage and memory function.

5. Digital output.

Based on the above features, the accuracy, stability, repeatability, and reliability of the intelligent pressure transmitter are all improved and improved. Its two-way communication capability realizes computer software control and remote range setting.

There are two main types of intelligent pressure transmitters: those with HART protocol and those with 482 or RS232 interfaces. Intelligent pressure transmitters with HART protocol superimpose a dedicated frequency signal on top of the analog signal to enable simultaneous communication between analog and digital. The intelligent pressure transmitter with RS232 or 485 port converts the analog signal A D inside and outputs it by a microprocessor calculation.

The development of pressure transmitters has gone through four stages:

1) Early pressure transmitters used a large displacement working principle, such as mercury float differential pressure gauge and diaphragm differential pressure transmitter, which were low accuracy and bulky.

2) In the 50s of the 20th century, there was a force balance differential pressure transmitter with slightly higher precision, but the feedback force is small, the structure is complex, and the reliability, stability and vibration resistance are poor.

3) In the mid-70s of the 20th century, with the emergence of new processes, new materials and new technologies, especially the rapid development of electronic technology, displacement transmitters with small size and simple structure appeared.

4) In the 90s of the 20th century, with the rapid development of science and technology, the measurement accuracy of transmitters was improved and gradually developed to intelligence, and digital signal transmission was more conducive to data acquisition.

Due to the different environment, medium, working principle, output signal, etc., the types are very different, and the characteristics are different. Pressure products are widely applicable and have been widely used in petrochemical, electric power and metallurgical industries.

1. According to the working principle of the sensor, it can be divided into resistance, capacitor, inductance, semiconductor, etc.;

2. According to the classification of sensor chips, it can be divided into ceramic, diffusion silicon, sapphire, etc.;

3. Classified from the measurement range, it can be divided into differential pressure, gauge pressure, absolute pressure, etc.;

Introducing several common pressure transmitters:

1. Diffusion silicon pressure transmitter: mature technology, small size, low **, gauge pressure measurement is the mainstream, and a small amount of absolute pressure, capacitive type is not enough to have poor anti-overload capacity, no corrosion resistance differential pressure can be selected, and low micro-range accuracy;

2. Ceramic pressure transmitter: low price, but low accuracy, micro range and large range are not selected, only suitable for gauge pressure measurement;

3. Sapphire pressure transmitter: the main advantage is that it can measure high-temperature medium, the temperature coefficient of the sensor is small, and the temperature drift is the lowest among these types of sensors. Sapphire can be up to 160 MPa, while diffusion silicon has a maximum range of 35 MPa;

4. Strain gauge pressure sensor: low cost, low sensitivity, low response frequency, large long-term drift, and some advantages in large-range measurement;

5. Quartz crystal pressure sensor: high-frequency response pressure sensor, which is only used for pressure measurement with specific requirements such as aerospace;

6. Sputtering film pressure sensor: high temperature resistance, stable and reliable, but due to the poor process and technology of domestic manufacturers, the product quality is unstable.