HH3151 HART Pressure Transmitter

HART pressure transmitter is the smart pressure transmitter in the process industry. With 4-20mA, HART. So, you can calibrate your pressure transmitters with HART communicators.

HART pressure transmitter

HART pressure transmitter configured through distributed control system (DCS) or HART communicator. The HART pressure transmitter is compatible with the Highway Addressable Remote Transmitter (HART) communication protocol. The HART function can transmit pressure transmitter data through an AC digital signal. The AC digital signal uses a 4-20mA analog output signal as a carrier. This eliminates the need for additional wires and connectors.

HH3151 HART Smart pressure transmitter that provides simplified field change, while communicating asset management data utilizing the latest HART 7 specification.

Sino-Inst offers a variety of HART pressure sensors for industrial pressure measurement. If you have any questions, please contact our sales engineers.

Features of HART pressure transmitter

HART pressure transmitter is a complete product line of liquid level, differential pressure, gauge pressure and absolute pressure transmitter. Models include flushing diaphragms and sanitary flanges for liquid level measurement, hydrostatic tank metering – HTG. And wetted parts of various materials to suit the process requirements.

3151 HART pressure transmitter
  • All models can be supplied with various remote seals.
  • Update output current in 100 ms with 0.75 µA/bit resolution;
  • Improved performance due to dedicated math co-processor;
  • Multi-drop operation mode;
  • PID control function;
  • Supports DTM and EDDL;
  • Bi-directional flow measurement;
  • With FMEDA analysis and MTBF of 244 year.

What is a HART transmitter?

HART transmitters are much more complicated.
The HART transmitter has the same pressure input and 4-20 mA output. But it also has an analog current loop output. The device contains some digital variables and settings. Access to these digital parameters requires the use of a HART configurator or communicator. This is essential for maintaining these devices.
Just like Hart Communicator 375.
In fact, many HART devices, cannot be maintained without access to digital parameters.

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What is HART calibrator?

HART calibrator is our HART communicator for calibrating instruments. For example pressure transmitter, DP transmitter, liquid level transmitter, flowmeter, and temperature transmitter.
HART communication protocol (Highway Addressable Remote Transducer) is a hybrid analog + digital industrial automation open protocol.
Its most significant advantage is that it can communicate through the traditional 4–20 mA analog instrument current loop, sharing only a pair of wires used by the analog host system.
We use this protocol in the HART calibrator.

HART communicator (such as HART 475) is the most common HART calibrator.
The proprietary calibration process ensures optimal temperature compensation. This limits the thermal impact on the sensor output.
It is suitable for the global process control industry. It provides a cost-effective solution for the use of conventional HART transmitters (such as the HART 475 field communicator).

HART protocol

What is HART pressure transmitter?

HART pressure transmitters

HART pressure transmitter for configuration via distributed control system (DCS) or HART communicator.

The HART pressure transmitter is compatible with the Highway Addressable Remote Transmitter (HART) communication protocol. This protocol is the most popular standard used by intelligent field devices and is used by the process control industry.
The HART function can transmit pressure transmitter data through AC digital signals. It uses 4-20mA analog output signals as a carrier. There is no need for additional wires and connectors.

HART pressure transmitter can also be used with a paperless recorder.

How to calibrate HART pressure transmitters

A pressure transmitter is one of the most common instruments in a process plant. To assure its accuracy, it needs to be calibrated.

But what do you need to calibrate it and how is it done?

You may know how to calibrate a pressure transmitter? Or, how to calibrate a differential pressure transmitter? Then, calibrate HART pressure transmitters, kind of like pressure transmitter calibration using a hart communicator. Pressure transmitter manufacturers have improved accuracy and technology, designed into these smart pressure measurement devices.

To calibrate a pressure transmitter, you need:

loop supply (if not connected to the controls system’s loop supply);
a pressure generator to generate input pressure;
an accurate calibrator to measure the input pressure;
an accurate calibrator to measure the output mA current.

Typically, the pressure transmitter is a HART protocol transmitter. So in case, there is any need to adjust/trim it, you will need to use a device supporting HART communication.

How to calibrate HART pressure transmitters?

Explaining how to do the calibration would result in quite a long text. So we have put together a video for you instead. The video shows you how to calibrate and trim a HART pressure transmitter. Please have a look at the video: How to calibrate HART pressure transmitters

Video source: https://www.youtube.com/watch?v=4wLCqH0M9fU&t=9s

HART Pressure Transmitters Calibration Steps

How to calibrate HART pressure transmitters?

Total Time:

1. Isolate the transmitter from the process being measured and its loop wiring.

2. If measuring the mA signal across the transmitter test diode leave the wires intact, but note this method does not give the best mA measurement accuracy.

3. Connect the mA measurement jacks of the 754 to the transmitter.

4. Connect the pressure module cable to the 475, and connect the transmitter test hose from the hand pump to the transmitter.
Press the HART button on the calibrator to see the configuration of the transmitter.

5. Press HART again and the calibrator will offer the correct measure/source combination for the test.

6. If documenting the calibration press As-Found, input the test tolerance and follow the prompts.

7. If the measured mA signal at the test points is found within tolerance the test is complete.
If not, change is required.
Select, adjust, and trim the pressure zero, mA output signal and input sensor.

If you still do not know, how to check the pressure transmitter?  Or, how to calibrate a pressure transmitter.

Just contact us.

HART pressure transmitter working principle

HART pressure transmitter is one type of smart pressure transmitter.

HART pressure transmitter connection

Principle and Application of Diffusion Silicon Pressure Transmitter

The pressure of the measured medium directly acts on the diaphragm of the sensor (stainless steel or ceramic). Causing the diaphragm to generate a micro-displacement proportional to the pressure of the medium. The resistance value of the sensor changes. The electronic circuit detects this change and converts and outputs a standard measurement signal corresponding to this pressure.

Principle of capacitive pressure transmitter

The capacitive pressure transmitter is mainly composed of a capacitance sensor and circuit board. The sensor implements pressure-capacitance conversion. The circuit board converts the capacitance to a two-wire 4-20mA. When the process pressure is applied to the isolation diaphragm from both sides (or one side) of the measuring chamber, it is transferred to the central diaphragm of the chamber through the silicone oil filling liquid. The central diaphragm is a diaphragm with tensioned edges. Under the action of pressure, a corresponding displacement is generated. This displacement creates a change in differential capacitance! And through the adjustment, oscillation, and amplification of the electronic circuit board! Converted into 4-20mA signal output! The output current is directly proportional to the process pressure!

pressure transducer often called a pressure transmitter, is a transducer that converts pressure into an analog electrical signal.

Although there are various types of pressure transducers, one of the most common is the strain-gage base transducer.

The conversion of pressure into an electrical signal is achieved by the physical deformation of strain gauges, which are bonded into the diaphragm of the pressure transducer, and wired into a Wheatstone bridge configuration.

Pressure applied to the pressure transducer produces a deflection of the diaphragm, which introduces strain to the gages.

The strain will produce an electrical resistance change proportional to the pressure.

In general, a pressure transmitter consists of three main components: a pressure sensor, a measuring circuit, and a process connection.

The main function of the pressure transmitter is to convert the physical parameters of the gas, liquid and other physical parameters of the pressure sensor into a standard electrical signal.

The standard electrical signal is more convenient for indicating the alarm device, the adjusting device, the recorder, and the secondary instrument.

Read more about Pressure Transmitter Working Principle

HART Smart Explosion Proof Pressure Transmitter

HART Explosion-proof pressure transmitters are available in a wide range of specifications. Easy to install and use, safe and explosion-proof.

They can be used in petrochemical, electric power, metallurgy, pharmaceutical, food processing, and other industries. Products follow the “IEC” standard. And explosion-proof pressure transmitters are renowned.

The company’s high-precision, high-stability pressure sensor assembly, through high-reliability amplifier circuit. And precision temperature compensation. The absolute or gauge pressure of the measured medium is converted into: 4 ~ 20mA, 0 ~ 5VDC, 0 ~ 10VDC and 1 ~ 5VDC,
and other standard electrical signals.

High-quality sensors hermetically sealed soldering technology and a complete assembly process, ensure excellent quality and performance.

Explosion-proof pressure transmitters are used in the following industries:

  • Compact explosion-proof pressure transmitter
  • Compact explosion-proof pressure transmitter
  • Industrial site process pressure detection
  • Laboratory pressure calibration system
  • Navigation and shipbuilding Aviation and aircraft manufacturing
  • Air separation equipment and thermal power unit
  • Energy management system
  • Hydraulic and pneumatic measurement and control system

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What are differential pressure transmitters?

Differential pressure (DP) transmitter, also called differential pressure transducer. Differential pressure transmitters measure the difference between two pressures. Sino-Instrument supplies Differential Pressure Transmitters For differential pressure measurement.

Differential Pressure Transmitters
For differential pressure measurement
pressure ranges 0 … 1 mbar up to 0 … 70 bar

Extended reading: Smart Differential Pressure Transmitter

Sino-Instrument offers over 10 hart Transducers. About 50% of these are 4-20ma Low-Pressure Transducers, 40% are Differential Pressure Gauge, and 20% are Diaphragm Seal Pressure transmitters, 20% are 4-20ma differential pressure transmitters.

Sino-Instrument sells through a mature distribution network that reaches all 50 states and 30 countries worldwide. HART Pressure Transmitter products are most popular in Domestic Market, Southeast Asia, and Mid East.  You can ensure product safety by selecting from certified suppliers, with ISO9001, ISO14001 certification.

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SMT3151DP Smart Differential Pressure Transmitter

Smart Differential Pressure Transmitter measures an industrial differential pressure. Can Works with diaphragm seals, capillary, HART. Outputs standard signals (such as 4 ~ 20mA, 0 ~ 5V).

A smart differential pressure transmitter is used to measure the liquid level, density, and pressure of liquid, gas, or steam. And then convert it into 4 ~ 20mA DC signal output. Smart can communicate with HART Communicator, and set and monitor through it. The DP transmitter is a transmitter that measures the pressure difference between the two ends of the transmitter. The differential pressure transmitter has two pressure interfaces. It is divided into a positive pressure end and a negative pressure end. In general, the pressure at the positive pressure end of the differential pressure transmitter should be greater than the pressure at the negative pressure end.

Sino-Inst offers a variety of samrt differential pressure senors for industrial pressure measurement. If you have any questions, please contact our sales engineers.

Features of SMT3151DP Smart Differential Pressure Transmitter

Blue and white custom housing smart differential pressure transmitter
  • Output signal 4-20mA output+HART communication;
  • Push Button Configuration;
  • Self-diagnosis capability;
  • Range coverage is 0-0.1KPa~41.0MPa;
  • Good stability, high precision, adjustable damping, strong resistance to one-way overload.
  • Explosion-proof housing structure.
  • LCD display

You may like the pressure level transmitter

SMT3151DP smart differential pressure is the pressure signal measured at the reference end of the low-pressure side. There are two ports connected to the processing pipeline.

Smart differential pressure transmitter is suitable for measuring pressure from -100mbar to 70bar. The maximum working pressure is up to 410bar. Sino-Inst’s SMT3151DP smart differential pressure transmitter is a rugged low-range / high-voltage line process differential pressure transmitter. Optional HART communication and 4-20 mA output provide an accurate measurement. Equipped with internal button adjustment for range and configuration and integrated LCD display.

Extended reading: How to calibrate HART pressure transmitters

Specifications of SMT3151DP Smart Differential Pressure Transmitter

Use object: liquid, gas or steam

Measuring a range of SMT3151DP smart differential pressure transmitter:

ModelTransmitter type
DPPressure transmitter
HPAbsolute pressure transmitter
CodeScale range
20-0.10~3.5kPa(0-10~350mmH2O)
30-0.8~8.0kPa(0-80~800mmH2O)
40-4.0~40kPa(0-400~4000mmH2O)
50-20~200kPa(0-2000~20000mmH2O)
60-70~700kPa(0-0.7~7kgf/cm2)
70-210~2100kPa(0-2.1~21kgf/cm2)
80-700~7000kPa(0-7.0~70kgf/cm2)
90-2.1~21MPa(0-21~210kgf/cm2)
00-4.1~41MPa(0-41~4100kgf/cm2)
CodeOutput form
ELinear output 4-20mAdc
SFLinear/square root output 4-20mAdc +HART signal,,Full function buttons on site
FMODBUS-485 signal
Structural materialsFlange connectorExhaust/Drain valveIsolation diaphragmFilling liquid
22316 Stainless steel316 Stainless steel316 Stainless steelSilicone oil
23316 Stainless steel316 Stainless steelHastelloy CSilicone oil
24316 Stainless steel316 Stainless steelMonelSilicone oil
25316 Stainless steel316 Stainless steelTantalumSilicone oil
33Hastelloy CHastelloy CHastelloy CSilicone oil
35Hastelloy CHastelloy CTantalumSilicone oil
44MonelMonelMonelSilicone oil
CodeShell materialConduit inlet dimensions
ALow copper aluminum alloy polyurethane coatingM20×1.5
BLow copper aluminum alloy polyurethane coating1/2-14 NPT
CStainless steelM20×1.5
DStainless steel1/2-14 NPT
CodePressure connection
L11/4NPT-18 Internal thread(excluding waist joint standard)
L21/2NPT-14 Internal thread
L3M20×1.5 External thread
CodeOptional parts
M4LCD multi – power digital display head
B1Pipe bending bracket
B2Plate bending bracket
B3Pipe mounting bracket
C02M20×1.5 nut and Φ 14 pressure short tube
C121/2NPT-14 external thread and Φ14 pressure short tube
C221/4NPT-18 external thread and Φ14 pressure short tube
C321/4NPT-18 to M20×1.5 external thread
C421/2NPT-14 to M20×1.5 external thread
C431/2NPT-14 to 1/4NPT-18 internal thread
C441/2NPT-14 to 1/2NPT-14 external thread
C451/2NPT-14 to G1/2 external thread
D1The side discharge valve is on the upper part
D2The side discharge valve is on the upper part
X1Oil ban
DaFlameproof ExdIIBT5Gb;(explosion-proof certificate no. : CE16.1163)
FaIntrinsically safe ExiaIICT4/T5/T6Ga;(explosion-proof certificate no. : CE15.2354X)

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Applications of Smart Differential Pressure Transmitter

SMT3151DP smart differential pressure transmitter is suitable for applications like:

Flow measurement;

Level monitoring;

Steam measurement;

Filter or pump differential pressure;

Critical process monitoring.

The common DP transmitter is the most commonly used test instrument in industrial process control.It is widely used in various automatic control systems.

Such as aerospace, military, petrochemical, chemical. Oil Wells, electric power, ships, building materials.Pipelines and many other industries.

Generally used in liquid, gas or steam differential pressure, flow measurement. The medium temperature is not too high, corrosion is not strong, viscosity is not high, not easy to crystallize and other environments.

If the working static pressure exceeds 13MPa, a high static differential pressure transmitter should be selected.

You may like: Differential Pressure Transmitter Installation Guide

The common DP transmitter is the most commonly used test instrument in industrial process control.It is widely used in various automatic control systems.

Such as aerospace, military, petrochemical, chemical. Oil Wells, electric power, ships, building materials.Pipelines and many other industries.

Generally used in liquid, gas or steam differential pressure, flow measurement. The medium temperature is not too high, corrosion is not strong, viscosity is not high, not easy to crystallize and other environments.

If the working static pressure exceeds 13MPa, a high static differential pressure transmitter should be selected.

You may like: Differential Pressure Transmitter Installation Guide

Differential pressure transmitter for liquid level measurement

Differential Pressure (DP) Level Measurement uses pressure readings and specific gravity to output level. DP Level is a common measurement technique that is used in a wide variety of applications. Solutions include standard transmitter connections and integrated transmitters with direct or remote mount seals that can be configured in tuned, balanced, and electronic systems. Additional Wireless options are also available.

More

Differential pressure transmitter for flow measurement

Differential Pressure Flow meters, also known as DP flow meters. Differential Pressure (DP) flow meters introduce a constriction in the pipe, that creates a pressure drop across the flow meter. The calculation of fluid flow rate, by reading the pressure loss across a pipe restriction, is the most used flow measurement technique in industrial applications. Differential pressure flow meters are suitable for water flow measurement, oil, steam or gas flow measurement.

More

Differential Pressure Transmitter Pdf

Smart pressure transmitter working principle

The working principle of the smart pressure transmitter (gauge pressure) / absolute pressure transmitter is:

The pressure passes through the isolated diaphragm and the pressure-conducting medium. It acts indirectly on the metal surface. The thickness of the metal film is different. As a result, the diaphragm is slightly deformed. The maximum shape variable does not exceed 0.1mm. A high-precision circuit that measures the deformation of the diaphragm converts this small deformation into a voltage signal proportional to the pressure. After linearization and temperature compensation processing, a dedicated chip is used to convert the voltage signal into an industry standard 4-20ma current signal or 1-5v voltage signal.

The metal capacitive pressure sensor used to measure the diaphragm detection circuit contains a linear circuit and a temperature compensation circuit. Therefore, the entire transmitter can achieve high accuracy and high stability. Metal capacitive pressure sensor has extremely high overload resistance. And has excellent performance in micro-pressure measurement.

Working principle of Smart differential pressure transmitter

SMT3151DP intelligent differential pressure transmitter uses advanced microprocessor technology and digital communication technology. The basic principle of differential pressure transmitter is: divide a space with sensitive elements (multi-purpose capsule) into two chambers. Introduce pressure into the two chambers separately. The sensor produces displacement (or displacement trend) under the combined action of the two pressures. This displacement is proportional to the pressure difference (differential pressure) between the two chambers. Convert this displacement into a standard signal output that can reflect the magnitude of the differential pressure.

You may like: differential pressure transmitter working principle|Working Principle of pressure level transmitters| differential pressure level transmitter working principle

Type selection of SMT3151DP smart differential pressure transmitter:

Before selecting the type, the User shall make clear:
The temperature. Corrosion. Measuring range. Use.
Whether the medium under test is explosion-proof.
Whether the oil shall be forbidden.
Whether the medium is easy to crystallize or thicken.
Whether the diaphragm flange connection is needed, etc.

Read more What is a diaphragm seal?

3 Methods for SMT3151DP Smart Differential Pressure Transmitter Application Measurement:

(1) The differential pressure transmitter is combined with the throttling device (like the orifice plate). To convert the flow rate according to the differential pressure value, generated before and after the throttling device.

SMT3151DP smart differential pressure transmitters supplier

(2) Measuring the height of the liquid by the pressure difference, generated by the gravity of the liquid itself.

(3) Directly measure the pressure difference between different pipes, and closed pressure vessels to convert the liquid level height.

The SMT3151DP smart series differential pressure transmitters are modular in design. And consist of a sensor module with an integrated electronic adapter unit. And an amplifier module with a local button unit.

The sensor module includes a differential pressure sensor and a temperature sensor for simultaneous measurement of differential pressure.

So the SMT3151DP smart series differential pressure transmitter has excellent static pressure characteristics and temperature characteristics.

Frequently
Asked
Questions

Smart transmitters work on the function of microprocessors for signal transmission.

Smart pressure transmitter consists of two parts: smart sensor and smart electronic board.

The intelligent sensor part includes: capacitive sensor, measuring diaphragm detection circuit, temperature sensor and temperature compensation circuit.

The part of the intelligent electronic board includes: a microcomputer controller and peripheral circuits. It completes the conversion of the pressure signal to 4-20mA dc.

Extended Reading: Digital Pressure Sensor-RS485

Depending on the type of pressure to be measured:

Pressure transmitter types include gauge pressure, absolute pressure, and differential pressure. Gauge pressure refers to the pressure that is less than or greater than atmospheric pressure based on the atmosphere. Absolute pressure refers to the absolute zero pressure as the reference and is higher than the absolute pressure. Differential pressure refers to the difference between two pressures.

According to the working principle of the pressure transmitter:

  • Strain Gauge Pressure Transducers
  • Capacitance Pressure Transducers
  • Potentiometric Pressure Transducers
  • Resonant Wire Pressure Transducers

Extended reading: Silicon Pressure Sensor

Simply put, a differential pressure transmitter is a device that measures two opposing pressures in a pipe or vessel. Differential Pressure (DP) transmitters measure the difference between two pressures. They use a reference point called the low-side pressure and compare it to the high-side pressure. Ports in the instrument are marked high-side and low-side. The DP reading can be either negative or positive depending on whether the low-side or high-side is the larger value. A DP transmitter can be used as a gauge pressure transmitter if the low-side is left open to the atmosphere.

Extended reading: Featured Diaphragm Seal Pressure Transmitters

The most common and useful industrial pressure measuring instrument is the differential pressure transmitter. This equipment will sense the difference in pressure between two ports and produce an output signal with reference to a calibrated pressure range.

The differential pressure transmitter can be used in combination with other accessories and can be used to measure liquid level and flow.

Differential pressure transmitters and pressure transmitters have many similarities. It can be mixed and used most of the time. As long as it is within the range of the differential pressure transmitter, it can measure not only positive pressure but also negative pressure. When measuring positive pressure, the negative port is open to atmosphere, and when measuring negative pressure, the positive port is open to atmosphere.

Differential pressure transmitters can also measure flow, pipeline pressure difference, tank liquid level, bubble water level, dust, or medium that is easy to crystallize and viscous and fluidity is not good.

Sino-Instrument is a leading manufacturer in the field of measurement and control in China.
One big reason for the continued growth of Sino-Instrument is our willingness to listen to our customers’ specific needs.

And develop solutions to meet those needs for the Oil and Gas, Power Generation, and Nuclear industries. In fact, many of the products we deliver are specially engineered to order. Such as pressure gauges, bimetal thermometers, thermocouples, pressure calibrators, bench pressures, etc.

It is widely used in electric power, petroleum, chemical, machinery, metallurgy, cement, glass, cooking, and other industries in various countries.

More products continue to be developed that integrate features, such as wireless and HART technologies (AMS TREX DEVICE). All our products are engineered and manufactured, at Sino-Instrument world headquarters located in Xi’an, China.

Sino-Instrument manufactures a wide variety of mechanical and electronic devices. To measure pressure, level measurement, temperature, and flow. And we’re working constantly to improve our product platform.

Sino-Instrument specializes in supplying electromagnetic flowmeters.
vortex flowmeter. gas turbine flowmeter. vortex flowmeter. orifice flowmeter. liquid turbine flowmeter. natural gas flowmeter. steam flowmeter. thermal gas flowmeter. elliptical gear flowmeter. magnetic flap level gauge. ultrasonic level gauge. diaphragm pressure gauge.
digital pressure gauge. diaphragm pressure gauge. stainless steel Series of flowmeters.

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SMT3151LT Differential pressure(DP) level transmitter

Differential pressure (DP) level transmitter is a perfect solution for tank level measurement. Flanges, seal diaphragms, capillaries, and DP transmitters are often used to measure liquid levels.

Differential pressure(DP) level transmitter is often used as a tank level transmitter. The DP transmitter is connected with a stainless steel flange by the capillary. Flange installation. The pressure is sensed by a remote transmission device installed on the container. The pressure is transmitted to the body of the transmitter through the capillary. The transmitter converts the pressure or differential pressure to 4 ~ 20mA. The DC signal is output. It can communicate for the setting and monitoring by cooperating with the HART communicator. Explosion-proof available.

Sino-Inst offers a variety of DP pressure transmitters for industrial pressure measurement. Connection with diaphragm seals. If you have any questions, please contact our sales engineers.

Features of Differential pressure (DP)level transmitter

  • The biggest feature of the differential pressure transmitter is that it can be easily installed on existing vessels. It can also be converted into a working tank or container.
  • The maintenance of the DP transmitter is easy because it can be isolated from the process by an isolation valve.
  • DP transmitter is ideal for liquid level measurement. It can also be used for light mud with an extended diaphragm, which can be installed flush on one side of the container.
  • Level measurement via DP transmitter is more cost-effective than other available sensors.
  • Since the DP transmitter is far away from the tank for liquid level measurement, it is easy to clean and maintain the tank.
  • The detection element takes up almost no space in the container. Instead, only two pressure holes need to be opened in the container wall.
  • There is no movable part in the detection part. Installation method, the work is more reliable.
  • The weight of the liquid column height per unit area is measured. The change of the measured medium weight will directly affect the measurement result. When the purpose of the measurement is to determine the weight storage of the material in the container. No additional amendments are required.
  • The use of flange pressure can solve the liquid level measurement of high viscosity, easy to crystallize, and medium with suspended matter. Evaporation and boiling liquid level can also be measured, but sometimes the error is large.
  • The display part of the instrument can usually adopt the general unit in the unit group instrument. No separate design is required.

There are four types of remote transmission devices for remote differential pressure transmitters:

  1. Flat type
  2. Thread mounting type
  3. Flange mounting type
  4. Extended Diaphragm Seal

Specifications of DP level transmitter

Measuring mediumLiquids, gases and steamPressure range0-0.1kpa-40mpa
Signal output4-20mA, superimposed Hart protocol, RS485Plywood materialAll 316L stainless steel
Supply voltage12-30VDCPrecision± 0.2% FS, ± 0.1% FS, ± 0.075% FS (customizable)
Diaphragm material316L, customizable Ha C, tantalum, Monel alloyTemperature compensation-10 ~ + 70 ℃
Long-term stability (1 year)≤ ± 0.25% FSOperating temperature-20 ~ + 100 ℃
Overload pressure200% FSZero rangeExternal continuously adjustable
Destruction pressure300% FSPower effectLess than 0.005% / V of output range
Weight3.9KG (standard type)Protection levelIP65
Volume uptakeLess than 0.16cm3Load impactIf the power supply is stable, the load has no effect

Applications of DP level transmitter

The differential pressure liquid level transmitter can prevent the measured medium from directly contacting the sensor diaphragm of the transmitter. It is suitable for the following situations:

  1.  When the measured medium has a corrosive effect on the transmitter connector and sensitive components;
  2. When the high temperature measured medium needs to be isolated from the transmitter;
  3. When there are solid suspended solids or high viscosity in the measured medium, it is easy to block the transmitter connector and the pressure chamber;
  4. When the measured medium is easily cured or crystallized by the pressure tube;
  5. When changing the measured medium needs to be rinsed and not to be mixed;
  6. Hygienic conditions must be maintained to prevent pollution. .
  7. Changing the measured medium requires strict purification of the measuring head
  8. Suspended liquid or high viscosity medium
  9. Measurement of sealed pressure vessel.

Read more What is a diaphragm seal?

Differential pressure type level transmitter working principle

Differential pressure (DP) level transmitter is a differential pressure transmitter to prevent the measured medium from directly acting on the transmitter. The differential pressure transmitter uses remote transmission isolation diaphragm contact. The remote transmission differential pressure transmitter (double flange) is composed of a differential pressure transmitter and a welded remote flange with capillary tube. Its working principle is the same as the differential pressure transmitter. Only the pressure transmission path is slightly different. The measurement diaphragm chamber of the transmitter is connected with a stainless steel capillary (tube with a diameter of about 3mm, plus protection) and the channel is several meters to tens of meters. One of the other places will be two (pressure or differential pressure) made into a flange-shaped measuring diaphragm box. The middle is filled with the transfer medium (silicone oil). When using, connect the flange to the device to measure.

SMT 3151 Differential Pressure Level Measurement

Differential pressure transmitter level measurement calculation

When using Differential pressure (DP) level transmitter to measure the liquid level as shown in the figure below.
The measured liquid density in the figure is ρ.
The working medium density in the capillary of the double flange differential pressure transmitter is ρ0.
The measuring range of the measured liquid level is H.
The center distance of the sampling tube of the measured liquid level is h.
It can be seen from the figure that the maximum measurement range of the liquid level △ P = P + —P- = H × ρ × g-h × ρ0 × g.

It can be seen from the formula that the dual-flange differential pressure transmitter should perform negative migration. The migration amount S is h × ρ0 × g. And the installation position of the double flange differential pressure transmitter has no effect on the migration amount and the measurement result.

The dual-flange differential pressure transmitter requires negative migration.

When the measured liquid level is 0, the pressure difference between the positive and negative measurement chambers of the remote differential pressure transmitter is the largest. The output current of the double flange differential pressure transmitter is 4mA.

As the measured liquid level rises, the pressure difference between the positive and negative measurement chambers of the transmitter gradually decreases.

When the measured liquid level rises to the highest Hmax. The pressure difference between the positive and negative measurement chambers of the transmitter is the smallest. The output current of the double flange differential pressure transmitter is 20mA.

Read more about Differential Pressure Transmitter Installation Guide

How to calibrate differential pressure transmitter for level

The differential pressure liquid level transmitter has been calibrated in the range, accuracy, linearity and other parameters according to customer requirements at the factory. And mark the range, accuracy, etc. on the nameplate of the differential pressure liquid level transmitter. As long as the density and other parameters of the measured medium meet the requirements of the nameplate, generally no adjustment is required.

If the customer needs to adjust the range or zero position, please adjust according to the following methods. Assuming that the range of the differential pressure liquid level transmitter is 0 ~ 10 meters:

How to calibrate a differential pressure level transmitter ?

  1. Unscrew the protective cover of the differential pressure liquid level transmitter. It can be adjusted by connecting external standard 24VDC power supply and ammeter (requires accuracy of 0.2% or above).

  2. When there is no liquid in the differential pressure liquid level transmitter. Adjust the zero potentiometer. Make it output current 4mA.

  3. Pressurize the differential pressure liquid level transmitter to full scale (10 meters). Adjust the full-scale resistor. Make it output current 20mA.

  4. Repeat the above steps two or three times until the signal is normal.

  5. Please input 25%, 50% and 75% signals to check the error of the differential pressure liquid level transmitter.

  6. For non-aqueous media. Differential pressure level transmitters are calibrated with water. It should be converted according to the pressure generated by the actual density of the medium. For example, when the medium density is 1.3, the 1.3m water level should be used to calibrate the 1m range.

  7. After adjustment, tighten the protective cover.

  8. The verification cycle of the differential pressure liquid level transmitter is once a year.

  9. HART intelligent differential pressure liquid level transmitter of Sino-Inst instrument can be selected. It is convenient to adjust the range of the differential pressure liquid level transmitter.

Extended reading: How to calibrate HART pressure transmitters

You may like: pressure level transmitter

What is the difference between pressure transmitter and differential pressure transmitter?

The principle of the pressure transmitter is: The medium pressure acts directly on the sensitive diaphragm. A Wheatstone bridge composed of resistors distributed on the sensitive diaphragm. The use of the piezoresistive effect realizes the conversion of pressure into an electrical signal. Amplify the millivolt signal generated by the sensitive element through an electronic circuit into an industrial (such as 4 ~ 20mA, 0 ~ 5V) standard signal. But the pressure transmitter has only one pressure interface.

Pressure transmitters

The principle of a differential pressure transmitter is: a transmitter that measures the pressure difference between the two ends of the transmitter. Output standard signals (such as 4 ~ 20mA, 0 ~ 5V). Differential pressure transmitters are different from general pressure transmitters in that they have two pressure interfaces. Differential pressure transmitters are generally divided into positive pressure end and negative pressure end. H is the positive pressure end and L is the low-pressure end. In general, the pressure at the positive pressure end of the differential pressure transmitter should be greater than the pressure in the negative pressure section to measure. Differential pressure transmitters are used to measure the level, density, and pressure of liquids, gases, and vapors. Then convert it into 4–20mA DC current signal output.

In summary: The fundamental difference between a pressure transmitter and a differential pressure transmitter is that the pressure transmitter can only measure the pressure at one pressure end. The differential pressure transmitter can measure the pressure at two pressure points, and the two pressures are subtracted. The pressure difference at the positive pressure end minus the negative pressure end pressure. Thus, the actual liquid level value is converted.

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Sino-Instrument (drurylandetheatre.com) offers over 100 DP transmitters for liquid level, pressure, flow, temperature measurement. Differential pressure (DP) level transmitters suit to measure water and another liquid level.

A wide variety of DP-level transmitters are available to you. Such as SMT3151LT Differential pressure level transmitter.

You can also choose from the liquid flow meters and pressure transmitters, not specified. We are a differential pressure level transmitter supplier, located in China. The top supplying country is China(Mainland), which supply 100% of DP transmitters respectively.

Differential pressure level transmitter is most popular for India, Pakistan, South Africa, The US. The quality is the same as the original premium quality. You can ensure product safety by selecting from our products, including IOS9000, … certification. You can find more information about our SMT3151LT DP Level transmitter, you can refer to our differential pressure level transmitter pdf:

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