SI-3151 Capacitive Pressure Transmitter

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SI-3151 Capacitive Pressure Transmitter

The SI-3151 series capacitive pressure transmitter is a high-performance intelligent pressure transmitter. It can measure both absolute and gauge pressure. Supports 4-20mA, HART, RS485 and other signal outputs.

The built-in linear and temperature compensation circuits enable the transmitter to achieve high accuracy of 0.5% FS and high stability. It also offers exceptional overload resistance.

RFQ NOW Pressure Sensors

Advantages of SI-3151 Capacitive Pressure Transmitter

Capacitive pressure sensors measure pressure using changes in the capacitance of a capacitor. They offer high accuracy, high sensitivity, low power consumption, excellent linearity, and a wide measurement range.

  • High Accuracy: Capacitive sensors provide very precise pressure measurements. An accuracy of 0.5% FS meets most pressure measurement needs.
  • High Sensitivity: They are extremely sensitive to pressure changes and can detect even small changes.
  • Low Power: Capacitive sensors typically require very little power to operate.
  • Excellent Linearity: The output signal shows a very good linear relationship with pressure changes.
  • Wide Range: They can accurately measure pressure from 25 Pa to 70 MPa with extremely high stability.
  • Strong Environmental Adaptability: They can operate stably in a wide range of environmental conditions, including high and low temperatures, humidity, and corrosive environments.
  • High Output Signal: The pressure transmitter’s circuitry converts small changes in capacitance directly into a high output signal without the need for signal amplification.

SI-3151 Capacitive Pressure Transmitter Specifications

Measuring mediumLiquid, gas or Steam;
Measure Range0-6.0～60MPaa
Accuracy class:0.1%FS, 0.25%FS, 0.5%FS
Overload capacity:Ranges 3 to 8 withstand 0 (absolute pressure) ~ 13.78MPa pressure transmitter without damage; range 9 pressure does not exceed 31.29MPa; range 0 pressure does not exceed 51.4MPa; normal working pressure is 3.43kPa (absolute pressure) to the upper limit of the range.
Long-term stability:Less than 0.25%FS/year, less than 0.5%FS/year
Power supply:15～36 VDC (standard voltage 24VDC)
output signal:(4～20)mA (two-wire system) HART communication
Display method:4-digit LCD display
Operation method:Comes with 3 buttons
Zero Span MigrationDirectly transfer the zero point and range by pressing the button
Operating temperature:(-40～80)℃ Compensation temperature: (-20～70)℃
Process connection:M20×1.5 external thread or specified by the user
Isolation diaphragm material:316 stainless steel, Monel, Hastelloy, etc. User notes.
Shell material:Aluminium Alloy
Protection class:IP65

Capacitive pressure Sensor working principle

A capacitive pressure transmitter is a measuring instrument that uses the principle of capacitance change to convert pressure signals into electrical signals. Its core component is a capacitive sensor, which measures the pressure of the medium by sensing the tiny displacement of a capacitor plate caused by the medium’s pressure.

In a capacitive pressure transmitter, the two pressures of the measured medium are passed into two high and low pressure chambers, acting on the isolation diaphragms on either side of the delta element (the sensitive element). These pressures are then transferred to both sides of the measuring diaphragm through the isolation diaphragms and the fill fluid within the element.

In a capacitive pressure transmitter, the measuring diaphragm and the electrodes on the insulating plates on either side form a capacitor. When the pressures on either side are inconsistent, the measuring diaphragm displaces. The displacement is proportional to the pressure difference, resulting in unequal capacitance on both sides. Through oscillation and demodulation, this displacement is converted into a signal proportional to the pressure.

The operating principles of capacitive pressure transmitters and capacitive absolute pressure transmitters are similar to those of differential pressure transmitters, except that the pressure in the low-pressure chamber is atmospheric pressure or vacuum.

The A/D converter in a capacitive pressure transmitter converts the demodulator’s current into a digital signal. Its value is used by the microprocessor to determine the input pressure value. The microprocessor controls the operation of the transmitter.

Read more about: Capacitive Pressure Transmitter/Differential Pressure Transmitter Structure

absolute pressure transmitter working principle

Order Guide

ModelTransmitter type
SI-3151GPPressure transmitter
SI-3151APAbsolute pressure transmitter
CodeScale range
(0~X)KPa0- 6.0～60MPa
CodeOutput form
ELinear output 4-20mAdc
SFLinear output 4-20mAdc+HART signal，Full function buttons on site
FMODBUS-485 signal
CodeStructural materials
Flange 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
D0The discharge valve is at the end
D1The side discharge valve is on the upper part
D2The side discharge valve is on the upper part
C02M20 x 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
X1Oil ban
GdMeasure the gold-plated membrane box
DaFlameproof  ExdIIBT5Gb;(explosion-proof certificate no. : CE16.1163)
FaIntrinsically safe ExiaIICT4 / T5 / T6Ga;(explosion-proof certificate no. : CE15.2354X)

Learn More About Capacitive Pressure Transmitter

According to different working principles, pressure transmitters can be divided into the following four types:

1. Piezoelectric transmetter. Piezoelectric transmitters are developed using the positive piezoelectric effect. The positive piezoelectric effect involves applying a certain external force to an electrolyte, causing it to deform. Polarization occurs within the electrolyte, generating positive and negative charges on its two surfaces. When the external force ceases, the electrolyte returns to a neutral state. The polarity of the charge changes with the direction of the applied force.

2. Strain gauge transmitter. Strain gauges are bonded together with adhesive to generate mechanical strain. When the force applied to the body changes, the resistance strain gauge also deforms, affecting the resistance and causing the voltage across the resistor to change.

3. Capacitive transmitter. Capacitive transducers are classified into two types: pneumatic and electric. The former outputs a gas pressure signal, while the latter uses a standardized DC input signal. Their specific working principles are described above.

4. Piezoresistive transmitter. Piezoresistive transducers apply pressure to the front surface of a diaphragm, causing the diaphragm to deform under the pressure. Thick-film resistors are printed on the back of the pressure-sensing diaphragm, forming a Wheatstone bridge. The piezoresistive effect generates a corresponding voltage signal across the bridge. This signal is directly proportional to the excitation voltage.

Absolute pressure transmitter is also a kind of pressure transmitter. However, the zero point of its starting pressure is absolute vacuum, and the pressure can be measured without internal vacuum at all. Absolute pressure transmitters are mainly suitable for measurement in cross-industry closed systems and places where altimeter measurement is required.

In the era of industrial automation, absolute pressure transmitters are widely used in:

  • Hydraulic and pneumatic control systems;
  • Petrochemical, environmental protection, air compression;
  • Power station operation inspection, locomotive braking system;
  • thermal power unit;
  • Light industry, mechanical metallurgy;
  • Building automation, constant pressure water supply system;
  • Other automation and detection systems;
  • Industrial process detection and control;
  • Laboratory pressure calibration, etc.

Speaking of the difference between absolute pressure transmitter and gauge pressure transmitter, you first understand the meaning of absolute pressure and gauge pressure.

Absolute pressure, or true pressure, is the pressure calculated from absolute zero pressure. Or the pressure calculated from the vacuum as the starting point. Absolute pressure, referred to as absolute pressure.

Gauge pressure, referred to as gauge pressure, refers to the pressure calculated from the local atmospheric pressure at that time. When the measured system pressure is equal to the local atmospheric pressure at that time, the pointer of the pressure gauge points to zero. That is, the gauge pressure is zero.

Vacuum degree, when the absolute pressure of the system being measured is less than the local atmospheric pressure at that time, the difference between the local atmospheric pressure and the absolute pressure of the system at that time is called the vacuum degree. The pressure measuring instrument used at this time is called a vacuum gauge.

Absolute pressure transmitter, we have explained above.
The gauge pressure transmitter is the most common pressure transmitter we often say.

The difference between absolute pressure transmitter and ordinary pressure transmitter

The scale of the starting point is different:
The starting point of an ordinary pressure transmitter, the zero point, is the pressure in the atmosphere. At this time, the bellows of the pressure transmitter is under the standard atmospheric pressure. , the output is 4ma.
The starting point for absolute pressure transmitters is absolute pressure. That is, the absolute pressure transmitter under atmospheric pressure displays the value of atmospheric pressure. The pressure at zero point 4ma at this time is absolute pressure zero.

The structure is different:
The diaphragm on the low pressure side of the absolute pressure transmitter is evacuated and has no air guide tube.
The low-pressure side diaphragm of ordinary pressure transmitters is directly in contact with the atmosphere, and usually has an air guide tube.

The measurement methods are different:
Ordinary pressure transmitters lead atmospheric pressure to one end of the pressure sensing element for comparison with the measured pressure. The difference between the two pressures is the measured pressure.
The pressure measured by the absolute pressure transmitter also needs to subtract the local atmospheric pressure.

If you cannot find an answer to your question in our SI-3151 Capacitive Pressure Transmitter, you can always contact us and we will be with you shortly.

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There are many types of pressure sensors, such as resistance strain gauge pressure sensors, semiconductor strain gauge pressure sensors, Silicon piezoresistive pressure sensors, inductive pressure sensors, capacitive pressure sensors, resonant pressure sensors and capacitive sensors.

Sino-Inst is a manufacturer of Capacitive Pressure Transmitters. SI-3151 Capacitive Pressure Transmitters adopts high-performance pressure-sensing chips. With advanced circuit processing and temperature compensation technology, it converts pressure changes into linear current or voltage signals .

If you need to purchase Capacitive Pressure Transmitters, or have any technical questions about Absolute Pressure Transmitters, please feel free to contact our engineers.

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    Popular Capacitive Pressure Transmitter GP-AP Best Price!

    The SI-3151 series capacitive pressure transmitter is a high-performance intelligent pressure transmitter. It can measure both absolute and gauge pressure. Supports 4-20mA, HART, RS485 and other signal outputs.

    Product SKU: SI-3151 Capacitive-Absolute Pressure Transmitter

    Product Brand: Sino-Inst

    Product Currency: USD

    Product Price: 265

    Price Valid Until: 2039-09-09

    Product In-Stock: InStock

    Editor's Rating:
    5