Category Archives: Smart Transmitters

SMT3151DP Smart Differential Pressure Transmitter

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The SMT3151DP Smart Differential Pressure Transmitter utilizes a single-crystal silicon sensor with German MEMS technology, offering higher measurement accuracy. It outputs standard signals (e.g., 4-20mA, 0-5V) and can also be configured with RS485 Modbus RTU or HART protocols.

SMT3151DP smart differential pressure transmitter

The single-crystal silicon sensor core features a dual-beam suspension design, significantly improving accuracy and resistance to unilateral and bilateral overload. A built-in intelligent signal processing module achieves perfect integration of static pressure and temperature compensation. This enhances measurement accuracy and long-term stability across a wide range of static pressure and temperature variations.

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

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Features

Blue and white custom housing smart differential pressure transmitter
  • Output signal 4-20mA output+RS485/HART communication;
  • 0.075%FS high accuracy, millisecond-level ultra-fast response;
  • Built-in three-button quick operation for on-site adjustment;
  • 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;
  • IP67 protection rating;
  • Intelligent static pressure compensation and temperature compensation protect the transmitter from the effects of temperature, static pressure, and overpressure, controlling the overall measurement error at the site within the specified parameters;
  • High static pressure resistance, up to 40MPa;

Extended reading: How to calibrate HART pressure transmitters

Technical Specifications

Measurement Range1KPa, 4KPa, 40KPa, 100KPa, 400KPa, 4MPa, 40MPa
Single-Side Overpressure16MPa
Dual-Side Static Pressure16MPa 25MPa 40MPa
Measurement Accuracy±0.075%, ±0.1%, ±0.5% (including linearity, hysteresis, and repeatability from zero)
Measured MediumGas, Liquid, Steam
Output Signal4~20mA DC+RS485/HART protocol
Power SupplyGeneral 10.5~45VDC, intrinsically safe explosion-proof 10.5-26VDC
Power Line Spacing15cm and above (avoid parallel wiring)
Saturation CurrentUpper limit 20.8mA, lower limit 3.8mA
Alarm CurrentUpper limit 22.8mA, lower limit 3.6mA (mode adjustable)
Adjustment FunctionZero and full-scale points can be adjusted locally via the three buttons on the top of the casing or remotely via configuration software
Zero ShiftCan be shifted within the range of -20% to +20% of the maximum range
Output MethodLinear output Square root output (can be remotely adjusted via configuration software)
Operating Temperature-40~85℃
Measured Medium Temperature:-40℃~120℃ (High temperature customizable)
Diaphragm Material316L stainless steel/Hastelloy alloy/Tantalum diaphragm/Gold-plated diaphragm
Position EffectApproximately 200Pa between horizontal and vertical positions
Response Time10ms
Static Pressure Effect< 0.05%FS/10MPa
Overpressure Effect< 0.05%FS/10MPa
Stability≤0.03%FS/year
Power Supply Effect< 0.005%FS/V
Explosion-Proof Rating:Exd Ⅱ CT6 Gb, Exia Ⅱ CT6 Ga
Enclosure Protection Rating:IP67

SMART Differential Pressure Transmitter Datasheet

SM3151DP-Differential-Pressure-TransmitterDownload

Order Guide

Use object: liquid, gas, or steam

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)

You may like: High temperature pressure transmitter | Magnetostrictive level sensor | Magnetostrictive level transmitter

Working principle of SMART differential pressure transmitter

The intelligent differential pressure transmitter uses a single-crystal silicon piezoresistive sensor as its core component. When pressure is applied to the sensor, the resistance of the single-crystal silicon changes, which is converted into an electrical signal by the circuit, and then digitally processed to output a standard signal (such as 4-20mA or a digital signal).

Its intelligent feature lies in its built-in microprocessor, which can perform temperature compensation, linear correction, and fault diagnosis, ensuring high measurement accuracy and stability.

The SMT3151DP intelligent differential pressure transmitter integrates differential pressure measurement, display, and signal output functions. This intelligent differential pressure transmitter is used to measure the level, density, flow rate, and pressure of liquids, gases, or vapors.

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

Smart Differential Pressure Transmitter Applications

SMT3151DP smart differential pressure transmitter is suitable for applications like:

https://www.drurylandetheatre.com/wp-content/uploads/2019/03/SMT3151DP-smart-differential-pressure-transmitters-manufacturer.mp4?_=1

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 16MPa, a high static differential pressure transmitter should be selected.

FAQ

Help Center

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.

More Featured Pressure Measurement Solutions

Piezoresistive Differential Pressure Transmitter
Flange Mounted Differential Pressure Transmitter
SI-702S Ultra-High Pressure Senors
SI-512H High Temperature Pressure Sensor
Differential Pressure Gauge
Differential pressure(DP) level transmitter
Remote Seal Differential Pressure Transmitter
Extended Diaphragm Seal DP Level Transmitter

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

Sino-Inst 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.

If you need to purchase Smart Differential Pressure Transmitters or have related technical questions, please feel free to contact our sales engineers!

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DP Level Transmitter for Tank Level Measurement

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The DP level transmitter works on the principle that the hydrostatic pressure difference of a liquid is directly proportional to the liquid level height. It calculates the liquid level by measuring the pressure difference of the medium inside the container and outputs a standard electrical signal. The dual-flange capillary structure provides mechanical and thermal isolation, allowing it to handle complex corrosive and high-temperature media in various industrial processes and tank level monitoring applications.

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

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More DP Transmitters

Features

  • Exd II CT6 Gb/ Exia II CT6 Ga, suitable for direct use in hazardous areas and outdoors;
  • All sensor components are made of 316L stainless steel;
  • 316 stainless steel diaphragm, convenient installation with movable flange;
  • 6 diaphragm materials available: 316L diaphragm, HC276 diaphragm, tantalum diaphragm, 316L fully coated diaphragm, gold-plated diaphragm, PTFE diaphragm, etc., customizable;
  • High-precision configuration, optional 0.1%FS, 0.075%FS;
  • Extremely high anti-interference and stability;
  • 275-point temperature, pressure, and current compensation;
  • LED LCD display, 0-100% percentage display, and real-time liquid level value display;
  • Output: 4-20mA + HART/RS485;
  • Nitrogen pressurized base, superior sealing performance, nitrogen pressurization prevents leakage.

Specifications of DP level transmitter

Measuring Medium:Gases, Vapors, Liquids
Measuring Range-100kPa…0~6kPa…7MPa
Accuracy:±0.075%, ±0.1%, ±0.2% (including linearity, hysteresis, and repeatability from zero point)
Stability:±0.2%/year
Power Supply:10–36V DC (24V DC recommended)
Reference Accuracy for Range Adjustment:If TD > 10 (TD = Maximum range / Adjustable range), then: ±(0.075 × TD)%
Ambient Temperature:-40℃ ~ 85℃
Measuring Medium Temperature:-40℃ ~ 400℃ (higher/lower temperatures can be customized)
Storage Temperature:-40℃ ~ 85℃
Display:LCD, OLED
Display Module Temperature:-20℃ ~ 70℃ (LCD), -40℃ ~ 80℃ (OLED)
Measuring Diaphragm:316L, Hastelloy C, Tantalum, Titanium, Nickel, Monel, Duplex Stainless Steel, PFA, Gold Plating
Process Connection:Stainless steel 316L, 304
Filling Fluid:Silicone oil, fluorinated oil, etc.
Transmitter Housing:Aluminum alloy material, epoxy resin coating on the surface
Housing Seal:Nitrile rubber
Nameplate:Stainless steel 304
Enclosure Protection Rating:IP67
Explosion Protection Rating:Exd Ⅱ CT6 Gb, Exia Ⅱ CT6 Ga
Measuring Range LimitsWithin the upper and lower limits of the range, it can be set arbitrarily, as long as the calibrated range ≥ the set range. It is recommended to choose a range with the lowest possible range ratio to optimize performance.
Influence of Mounting PositionChanges in installation position will cause zero point influence, which can be corrected by zero adjustment; there is no range influence.
OutputTwo-wire 4-20mA, compliant with NAMUR NE43 standard, superimposed digital signal (Hart protocol)
Output Signal LimitsImin (minimum): 3.9mA Imax (maximum) = 21.0mA
Alarm CurrentLow alarm mode (minimum): 3.9mA High alarm mode (maximum): 21mA (user pre-settable)
Default Alarm Current SettingHigh alarm mode
Fault WarningIf the sensor or circuit fails, the automatic diagnostic function automatically outputs 22.0mA
Response TimeAmplifier component damping constant is 0.1s; sensor time constant is 0.1–1.6s, depending on the range and range ratio. Additional adjustable time constant: 0–100s
Warm-up Time<15s

There are 5 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
  5. Wet legs/Dry legs
SM3151LT liquid level pressure-differential pressure transmitterDownload

Applications of DP level transmitters

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?

DP level transmitter working principle

The differential pressure level transmitter is an instrument that uses the pressure generated by the liquid column to measure the height of the liquid level. When the liquid level changes, the pressure received by the diaphragm at the high-pressure side flange will change accordingly. The differential pressure value calculated by the transmitter will also change accordingly. There is a linear relationship between them.

Normally, the high-pressure side (H side) and the low-pressure side (L side) cannot be installed reversely. Generally, the H side is installed at the lower part of the equipment, and the L side is installed at the higher part of the equipment. Before installation, the flange surface of the equipment should be cleaned and the gasket should not be placed off-center to prevent the diaphragm from being punctured or deformed, causing distortion of the transmitter.

SMT 3151 Differential Pressure Level Measurement

Differential pressure transmitter level measurement calculation

When using a 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

DP level transmitter calibration

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:

https://www.drurylandetheatre.com/wp-content/uploads/2019/03/SMT-3151-Differential-Pressure-Level-Measurement-supplier.mp4
  1. Unscrew the protective cover of the differential pressure liquid level transmitter. It can be adjusted by connecting an 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 potentiometers. Make it output a current of 4mA.
  3. Pressurize the differential pressure liquid level transmitter to full scale (10 meters). Adjust the full-scale resistor. Make it output a current of 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

More Featured DP Transmitters

Smart Differential Pressure Transmitter
Flange Mounted DP Transmitter
Extended Diaphragm Seal DP Level Transmitter
Remote Seal Differential Pressure Transmitter

More Pressure and Level Measurement Solutions

Sino-Inst (drurylandetheatre.com) offers over 20 DP transmitters for liquid level, pressure, flow, and density measurement. Differential pressure (DP) level transmitters are suitable for measuring water and other liquid levels.

We are a differential pressure level transmitter supplier, located in China. Our products are widely exported to the United States, Australia, Singapore, Indonesia, etc. You can ensure product safety by selecting from our products, including IOS9000, and… certification.

Of course, in addition to differential pressure transmitters, pressure transmitters can also be used to measure the liquid level in open tanks. If you need to purchase Level Transmitters or have related technical questions, please feel free to contact our sales engineers!

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