What are the uses and characteristics of differential pressure transmitters?

10 smart features of microdifferential pressure transmitters.

Micro differential pressure transmitter is a new type of transmitter produced by Nanjing Nugget Technology Co., Ltd. with foreign advanced technology and equipment, key raw materials, components and parts are imported, the whole machine has been strictly assembled and tested, and the micro differential pressure transmitter has the characteristics of advanced design principle, complete varieties and specifications, easy installation and use. Specifically, the differential pressure transmitter has the following 10 intelligent features:

1. Super measurement performance, used for pressure, differential pressure, liquid level, flow measurement.

2. Digital accuracy: + (analog accuracy: + (full performance: +(3. Stability: months.)

4. Range ratio: 100:1

5. Measurement rate:

6. Miniaturization (all stainless steel flange, easy to install.)

7. The process connection is compatible with other products to achieve the best measurement.

8. The only sensor in the world with H alloy sheath (patented technology) has achieved excellent cold and thermal stability.

9. Intelligent transmitter using 16-bit computer.

10. Standard 4-20mA, with digital signal based on HART protocol, remote control, support to upgrade to fieldbus and field-based control technology.

As the name suggests, the differential pressure measures the difference between the pressure between two impulse tubes, and it is also called the differential pressure because the pressure is at the same level. It should be characterized by low pressure, and the sensor used is better than that of ordinary sensors.

The working principle of the differential pressure transmitter is that the two pressures of the measured medium pass into the high and low pressure chambers, act on the isolation diaphragm on both sides of the δ element, and are transmitted to both sides of the measuring diaphragm through the isolation sheet and the filling liquid in the element. The measuring diaphragm and the electrodes on the insulating sheets on both sides form a capacitor.

When the pressure on both sides is inconsistent, the displacement of the measuring diaphragm is proportional to the pressure difference, so the capacitance on both sides is unequal, and it is converted into a signal proportional to the pressure through the oscillation and demodulation links. Pressure transmitters and absolute pressure transmitters work on the same principle as differential pressure transmitters, except that the pressure in the low-pressure chamber is atmospheric or vacuum.

A D converter converts the current from the demodulator into a digital signal, the value of which is used by the microprocessor to determine the input pressure value. The microprocessor controls the operation of the transmitter. In addition, it performs sensor linearization.

Reset the measurement range. Calculations such as conversion, damping, prescribing, sensor fine-tuning, as well as diagnostics and digital communication.

Features of differential pressure transmitters:

Differential pressure transmitters are used to measure the level, density and pressure of liquids, gases and vapors, which are then converted into a current signal output of 4-20mA DC.

The JT-3051DP can also communicate with each other via a Brain communicator or a Centum CS XL or HART 275 communicator for setting and monitoring.

The transmitter is mainly composed of a detection part and a signal conversion and amplification processing part. The detection part is composed of a detection diaphragm and a fixed arc plate on both sides, the detection diaphragm can move axially under the effect of pressure difference to form a movable capacitor plate, and two variable capacitors C1 and C2 are formed with the fixed arc plate, and before detection, the pressure of the high and low pressure chambers is balanced, P1 = P2; According to the structural requirements, the fixed arc-shaped plates and the detection diaphragm composed of two variable capacitors are symmetrical, and the pole spacing is equal, C1 = C2. When the measured pressures P1 and P2 enter the high and low pressure chambers from the induction tube, the volume of the high pressure side will be reduced due to the displacement of the center of the P1 > P2 isolation diaphragm, compressing the electrolyte.

When the electrolyte is incompressible, the volume change will cause the center of the detection diaphragm to shift to the low-pressure side, which is equal to the displacement of the center of the isolation diaphragm. According to electrical engineering, when the pole spacing of the two poles that make up the capacitor changes, its capacitance will also change, i.e., from C1=C2 to C1≠C2. As can be seen from the electrical schematic diagram, when no displacement occurs, i1=i2=0; ι1+ι2=ιc;After the displacement occurs, due to the change of the relative pole spacing, the amount of charge accumulated on each plate also changes, forming a charge displacement, which reflects i1 ≠ i2, and the current difference between the two will be generated, and if the value and the relationship with the pressure difference are detected, the flow rate can be calculated.

Capacitive differential pressure transmitter is a new type of differential pressure transmitter developed in the 80s of the 20th century, which uses a single crystal silicon resonant sensor and adopts microelectronic surface processing technology, in addition to ensuring the measurement accuracy, it can also resist the influence of static pressure and temperature drift. Equipped with low-noise modems and open communication protocols, today's capacitive differential pressure transmitters enable digital lossless signal transmission.

The differential pressure transmitter is the most commonly used weight transmitter in industrial practice, which is widely used in various industrial automatic control environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production automation, aerospace, military industry, petrochemical, oil wells, electric power, ships, machine tools, pipelines and many other industries.

Strain gauge differential pressure transmitter principle and application.

There are many types of mechanical transmitters, such as resistance strain gauge differential pressure transmitters, semiconductor strain gauge differential pressure transmitters, piezoresistive differential pressure transmitters, inductive differential pressure transmitters, capacitive differential pressure transmitters, resonant differential pressure transmitters and capacitive accelerometers. However, the most widely used is the piezoresistive differential pressure transmitter, which has very low ** and high accuracy as well as good linearity. Let's focus on these sensors.

When we look at piezoresistive force transducers, we first look at the resistance strain gauge. An electrical strain gauge is a sensitive device that converts the strain change on a test piece into an electrical signal. It is one of the main components of piezoresistive strain transmitters.

There are two most widely used types of electrical strain gauges: metal resistance strain gauges and semiconductor strain gauges. There are two types of metal resistance strain gauges: wire strain gauges and metal foil strain gauges. Usually the strain gauge is tightly bonded on the mechanical strain matrix through a special adhesive, when the matrix is stressed and the stress changes, the resistance strain gauge also produces deformation together, so that the resistance value of the strain gauge changes, so that the voltage applied to the resistor changes.

The resistance change produced by this strain gauge is usually small when it is stressed, and generally this strain gauge forms a strain bridge, which is amplified by a subsequent instrumentation amplifier and then transmitted to the processing circuit (usually AD conversion and CPU) display or actuator.

The basic principle of a differential pressure transmitter is to divide a space-sensitive element (multi-purpose diaphragm box) into two chambers, and when pressure is introduced into the two chambers respectively, the sensor will produce a displacement (or displacement trend) under the joint action of the two pressures, and this displacement is proportional to the pressure difference between the two chambers (differential pressure), and this displacement is converted into a standard signal output that can reflect the magnitude of the differential pressure.

In practice, there are many different types of sensitive element structure, chamber form, displacement conversion method, and standard signal format.

Differential pressure transmitters.

It is a typical self-balancing detection instrument, which uses the working principle of negative feedback to overcome the influence of unfavorable factors such as component materials and processing technology. The working principle of the differential pressure transmitter: the differential pressure from the double-sided impulse tube acts directly on the isolation diaphragm on both sides of the transmitter sensor, and conducts the sealing liquid in the diaphragm to the measuring cell, and the measuring cell converts the measured differential pressure signal into the corresponding electrical signal and transmits it to the converter.

After amplification and other processing, it becomes a standard electrical signal output.

The differential pressure from the two-sided impulse tube directly acts on the isolation diaphragm on both sides of the transmitter sensor, and conducts the sealing liquid in the diaphragm to the measuring cell, and the measuring cell converts the measured differential pressure signal into the corresponding electrical signal and transmits it to the converter, which becomes a standard 4-20mA electrical signal output after amplification and other processing.

Many people do not understand the differential pressure transmitter, so for how to use the differential pressure transmitter, what need to be paid attention to during the use of the Yu He is also not clear, blind wrong use, not only difficult to play the function of the transmitter, but also to speed up the damage of the equipment, today we will fill this knowledge blind spot for you.

Before installation, check whether there are any signal interference sources around the differential pressure transmitter, stay away from these interference sources, or remove the sensor line to connect to the metal housing as much as possible to enhance the anti-interference ability.

The differential pressure transmitter should be cleaned regularly to ensure that the surface is clean, which is not only beautiful, but also prevents the transmitter from being in contact with the corrosive medium for a long time, causing damage to the equipment.

When wiring the product, the cable should be passed through the waterproof joint (accessory) or winding pipe and the sealing nut should be tightened to prevent rainwater from leaking into the transmitter housing through the cable.

The differential pressure transmitter should have a pressure tap at the top of the process pipe, and the transmitter should be installed on the upper part of the process pipe so that the liquid can be quickly injected into the process pipe.

In winter, it is necessary to take antifreeze measures for the differential pressure transmitter installed outdoors to prevent the liquid in the induction port from expanding in volume due to icing and damaging the sensor or diaphragm.

When measuring high-temperature media such as steam, it is necessary to install a condenser to avoid the adverse impact of the working temperature on the equipment, and an appropriate amount of water needs to be injected into the buffer pipe to cool down when the steam is in contact with the transmitter.

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.