What Is an Air Pressure Transducer?

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An Air pressure transducer is a sensor that converts the mechanical signal of air pressure into a current signal. Pressure has a linear relationship with voltage or current, and it is generally proportional. Therefore, the output voltage or current of the transmitter increases as the pressure increases. From this, a relationship between pressure and voltage or current is derived.

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What is an air pressure transducer?

Featured air pressure transducers

SI-300 Pressure Transducer 4-20mA/Voltage
The 4-20mA/ Voltage Pressure Transducer,
also called pressure transmitter 4-20mA,
is a pressure sensor with4-20ma/Voltage output.
SI-390 Industrial Pressure Transmitter
Pressure transmitters for general industrial applicaitons. -0.1kPa ~ 0 ~ 0.01kPa ~ 100MPa ~150MPa. 0.1% FS, 0.25% FS, 0.5% FS. 4-20mA (2-wire system), 0-5 / 1-5 / 0-10V (3-wire
SI-503K Gas Pressure Sensor
Gas pressure sensor for industrial gas pressure monitoring. Pagoda gas nozzle Φ8. Such sensors are also commonly referred to as wind pressure transmitters, exhaust pressure sensors.
SI-702 High Pressure Sensor
High pressure sensor is pressure transmitter designed for high pressure measure&control. 0 ～ 40MPa… 600MPa. M20 × 1.5, G1 / 2 (others are customized according to requirements)
SI-702S Ultra-High Pressure Senors
Pressure sensor for Ultra high pressure applications. Ultra high pressures up to 15,00MPa. 0-2000MPa to 0-7000MPa (customized).Ball head M20 × 1.5, cone head M20 × 1.5.
SI-512H High Temperature Pressure Sensor
High Temperature Pressure Sensor for pressure measurement of high temperature gas or liquid. Such as steam pressure. High temperature up to 800 ℃.
SIJC-1000HSM-Silicon Pressure Sensor
Silicon pressure sensor, also known as Diffused silicon pressure sensor. Silicon pressure sensors are low cost.
SI-706 Combined Pressure and Temperature Sensor-Dual function
Combined pressure and temperature sensor for Simultaneous measurement of pressure and temperature.
Thermocouple types: J, K, E type or PT100 platinum resistance. Two outputs do not affect each other. 
Absolute Pressure Transmitter
Absolute pressure transmitter with 4-20mA output for measuring pressure with absolute type reference. Absolute pressure (AP) transmitter is a measure of the ideal (complete) vacuum pressure.
Hydrostatic pressure transmitter
Hydrostatic pressure transmitter is used for fluid hydrostatic pressure measurement. With working static pressure up to 32Mpa, for liquid, gas or steam .

Pressure transducer is a high-precision instrument that can perform on-site inspection of pressure parameters, and is widely used in industrial measurement and control processes. It can be used to measure the pressure, differential pressure and absolute pressure of various media such as liquid, gas and steam. Then the pressure signal is converted into 4-20mADC signal output to supply secondary instruments such as indicating alarm, recorder, regulator, etc. for measurement, indication and process adjustment.

Extended reading: extrusion melt pressure transducer

The functional principle of a resistive pressure transmitter is very simple. The pressure sensor converts the mechanical pressure value into a proportional electrical signal. The pressure sensor typically consists of a stable main body and a (thin) diaphragm.

The diaphragm is the most important element for the measurement of pressure and is equipped with strain-sensitive and compression-sensitive resistance structures, so-called strain gauges (DMS). The diaphragm is deflected under the influence of pressure. 

Thus, the strain gauges attached to it are elongated or compressed and its electrical resistance changes. This change in resistance is directly proportional to the pressure.  For example, if the resistors are wired to a Wheatstone measuring bridge, the resulting electrical signal can be measured and transferred to an indicator.

Extended reading: Pressure indicator transmitters

Read more about: What is a pressure sensor and how it works? 

There are different types of pressure transducers based on their design.

These sensors can come in several shapes and sizes, but the technology inside can also differ. 

There 4 main types of pressure sensors based on this: 

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

More about Industrial Pressure Sensors

Extended Reading: Electronic Pressure Switch for Air Compressor

The terms pressure sensor, pressure transducer and pressure transmitter are often used interchangeably. We usually define relevant measurement parameters and output signals to distinguish products.

Of course, if you want to strictly distinguish these three words from a technical point of view, you can refer to the following brief introduction:

PRESSURE SENSOR

Millivolt (mV) output signal (also a general term for all pressure types); a device that measures pressure.

The millivolt output signal can typically be used ten (10) to (20) feet away from the electronics without significant signal loss. The signal is proportional to the supply. A 5VDC supply with a 10mV/V output signal produces a 0-50mV output signal.

Older technologies such as bonded foil strain gage or thin film technology produce 2-3mV/V (millivolts per volt), whereas MEMS technology can produce 20mV/V reliably.

Millivolt output signals give the design engineer the flexibility to condition the output signal as their system needs it and can reduce package size and cost.

Extended Reading: 4-20ma pressure transducer wiring diagram

PRESSURE TRANSDUCER

High level voltage or frequency output signal including 0.5 to 4.5V ratiometric (output signal is proportional to the supply), 1-5V and 1-6kHz. These output signals should be used within twenty (20) feet of the electronics.

Voltage output signals can offer low current consumption for remote battery operated equipment such as wellhead SCADA systems.

Supply voltages are typically from 8-28VDC, except for the 0.5-4.5V output, which requires a 5VDC regulated supply.

Older voltage output signals, such as 0-5V, do not have a “live zero” where there is signal when the sensor is at zero pressure. The risk is that the system does not know the difference between a failed sensor with no output and zero pressure.

Extended Reading: Smart pressure transmitter

PRESSURE TRANSMITTER

Current output signal, i.e. 4-20mA (4 to 20mA), the current, rather than the voltage, is measured on the device, rather than the voltage; Sino-Inst pressure transmitters are two wire devices (red for supply, black for the ground).

4-20mA pressure transmitters offer good electrical noise immunity (EMI/RFI), and will need a power supply of 8-28VDC. Because the signal is producing current, it can consume more battery life if operating at full pressure.

Extended reading: Pressure Sensor Applications In Various Industries

Pressure Transducer is a device or device that can sense the pressure signal and convert the pressure signal into a usable output electrical signal according to a certain law. Pressure sensors are usually composed of pressure sensitive elements and signal processing units. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors.

Pressure sensor is the most commonly used sensor in industrial practice. It is widely used in various industrial automation environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production automation, aerospace, military, petrochemical, oil wells, electric power, ships, machine tools , pipeline and many other industries, the following briefly introduces some common sensor principles and their applications. Another medical pressure sensor.

Our pressure transmitters can also be upgraded to Low power-battery powered Wireless Pressure Sensors.

The pressure switch adopts high-precision, high-stability pressure sensor and transmission circuit, and then uses the CPU modular signal processing technology to realize the detection, display, alarm and control signal output of the medium pressure signal.

Pressure switches can be widely used in petroleum, chemical, metallurgy, electric power, water supply and other fields to measure and control the gauge pressure and absolute pressure of various gases and liquids. It is an ideal intelligent measurement and control instrument for industrial sites. Pressure switches are widely used in aerospace and military fields, such as M1A1 tanks, Apollo spacecraft, Boeing 747, Airbus A320, F22, F117 and other product manufacturing.

A pressure switch is not the same as a pressure sensor:

(1) The pressure sensor is composed of a pressure-sensitive element and a conversion circuit. It uses the pressure of the measured medium to impregnate the pressure-sensitive element to produce a small changing current or voltage output.
(2) The pressure switch is a utility switch that automatically turns on or off when the set value is reached.

Extended Reading: strain gauge pressure transducer

What is the difference between a pressure switch and a pressure sensor

  1. Difference in function

(1) As the name suggests, the pressure switch is a switch. It is just that the pressure is set in advance. When the measured medium reaches this pressure, the switch can be turned on or off automatically. The pressure switch must be given a pressure value in advance, and then open or close the switch. It is used for simple control, and it is all switching output.

(2) The pressure sensor can not only output analog signals, but also output digital signals. Digital signal processing is more convenient, and it can also be transmitted remotely. The pressure sensor is composed of a pressure-sensitive element and a conversion circuit. The pressure of the measured medium acts on the pressure-sensitive element to generate a small change of current or voltage output.

  1. Price difference

The pressure sensor is naturally much more expensive than the pressure switch. Because the pressure sensor has an internal signal conditioning circuit. Considering the service life and safety, the pressure sensor is much more cost-effective than the pressure switch. The after-sales service, product reputation, The market difference is better than the pressure switch. Obviously, the pressure sensor is still the priority.

  1. Differences in the mode of action

(1) The sensor often needs to be used in conjunction with an external amplifier circuit to complete the process from pressure detection to control and display. Since the pressure sensor is a primary component, the signal fed back by the pressure sensor needs to be processed, analyzed, stored, and controlled through the measurement and control system, so that industrial automation equipment and project operation control are more intelligent.

(2) The pressure switch does not need other cooperation. When the pressure is sensed, it can complete the work independently.

Extended reading: How to calibrate HART pressure transmitters

Air pressure transducer selection:

  1. Measuring range (range)
  2. The output signal, communication protocol, whether with display meter
  3. Process interface (general, please provide thread specifications, flange type, provide specific flange standard, flange size, capillary length, process medium temperature, and other information)
  4. Electrical interface
  5. Installation method (horizontal installation or vertical installation)
  6. Mounting bracket (flat bracket or L-shaped bracket, bracket material requirement: carbon steel or stainless steel)
  7. Other requirements (explosion-proof, explosion-proof, lightning arrester, water, and oil prohibition treatment, etc.)

Read more about Gas Pressure Transducer-Sensor for Gas Pressure Measurement 

Tools for converting and calculating pressure values

Absolute pressure-Gauge pressure ConverterPressure Unit ConverterLiquid Depth/Level to Hydrostatic Pressure Calculator
Differential Pressure CalculatorPressure Transducer 4-20ma Output CalculatorPressure to Liquid Level Calculator

More Pressure Measurement Products

Diaphragm Seal Pressure Transmitter
SI2088-W Wireless Pressure Transmitter
SI-1110 Wireless Pressure Transducer
Differential pressure(DP) level transmitter
SI-151 Hydrostatic Level Sensor
Wireless Level Sensor – LoRa 
Flange Mounted Differential Pressure Transmitter
Extended Diaphragm Seal DP Level Transmitter
Remote Seal Differential Pressure Transmitter
Differential pressure(DP) level transmitter
SI-PCM260 Deep Well Water Level Sensor
SI-302 Anti-corrosive Submersible Level Transmitter

Frequently
Asked
Questions

Help Center

Here we briefly introduce the use of some pressure transmitters;

  1. It is directly used for the measurement of various pressures: air pressure, water pressure, hydraulic pressure (including water pressure), various blood pressure measurement of people in life, etc.;
  2. Pressure sensors are used in automobiles, some high-end motorcycles and almost all internal combustion engines;
  3. Liquid level meter: Most of the field meters used for various liquid level measurement are also pressure sensors;
  4. The source of the weighing signal of most electronic weighing scales and truck scales is also the pressure sensor.
  5. Pressure sensors are also used for acceleration measurement in aviation and aerospace.

There are many others, too many to list.

There are two measurement methods:

  1. Pass the current test of the multimeter, the steps are as follows:
  • The red test lead of the multimeter is connected to the hole of mA, and the black test lead is connected to COM.​​
  • Adjust the gear of the multimeter to the DC mA gear.
  • The red test lead of the multimeter is connected to the positive pole of the 4-20mA sensor output, and the black test lead is connected to the negative pole of the 4-20mA sensor output.
  • Read the reading from the display area of ​​the multimeter, and the reading is the current value.
  1. Through the multimeter’s 10,000-voltage range measurement, for the multimeter without the current test function, the current value can be measured by the voltage, and the steps are as follows:
  • At the output of the 4-20mA sensor, connect a sampling resistor of about 100 ohms.
  • The red test lead of the multimeter is connected to the hole of mA, and the black test lead is connected to COM.​​
  • Adjust the gear of the multimeter to DC V gear.
  • The red test lead of the multimeter is connected to the positive pole of the 4-20mA sensor output, and the black test lead is connected to the negative pole of the 4-20mA sensor output.
  • Read the reading from the display area of ​​the multimeter, the reading is the voltage value, and the current value can be obtained by dividing the reading reading by the resistance value (such as 100 ohms).

Use the DC current function of the multimeter, 20mA gear (if not, choose 100mA gear), and you can directly test the sensor output. If it is a desktop digital multimeter, you can also use any sensor function to allow the instrument to directly test the physical quantity sensed by your sensor. Wiring method: red test lead to green wire, black test lead to yellow wire

The basic principle of the differential pressure transmitter is to divide a space with a sensitive element (multi-purpose bellows) into two chambers. When pressure is introduced into the two chambers, respectively, the sensor produces displacement (or a tendency to displace) 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.

Read more about: What Is A Differential Pressure Transmitter?

  1. Potentiometer-based calibration
    Some pressure sensors have screws for zero adjustment, span adjustment, or both. Turning these screws will adjust the low end output (zero adjustment) or the high end output (span adjustment).

Typically, these screws are located on the PCB inside the sensor body. If you want to adjust the output, you need to follow these steps:

Turn on the sensor without disconnecting the PCB output port.
Accurately apply zero and full scale pressure to the sensor. (A minimum ±0.1% full scale accuracy of applied pressure is recommended.)
Connect the sensor to appropriate power and monitoring equipment to verify the output of the pressure sensor.
Adjust the zero output first, then adjust the full scale output.
Tools such as DC power supply, multimeter, pressure comparator are required.

  1. Electromagnetic based calibration
    Instead of using potentiometers, some pressure sensors use magnets for decay. Magnet-based calibration comes in two flavors: magnet and shunt calibration (often called shunt calibration).

A small magnet is usually placed near the top or bottom of the pressure sensor to increase or decrease (respectively) the zero output of the pressure sensor. Generally speaking, the full-scale output of this type of sensor can usually only be adjusted by the factory. If you want to adjust, you need to follow the steps below:

Precisely apply zero pressure to the sensor. (We recommend a full-scale accuracy of at least ±0.1% of applied pressure.)
Connect the sensor to appropriate power and monitoring equipment to verify sensor output.
To turn down the zero output, hold the magnet perpendicular to the lower end of the device.
To turn up the zero output, hold the magnet perpendicular to the upper end of the device.
If the zero output is 0 (eg, 0 VDC, 0 mV, etc.), the magnet adjustment of the zero output can be a bit of a hassle. When the zero output is non-zero, on a 1-5 VDC sensor, the actual value is less than the zero output (0.995 VDC, 0.85 VDC), so you can tell when the value is adjusted too far and the output needs to be restored. When the zero output is 0, there is no that extra buffer below the zero output and can be adjusted to a value that can only be pulled back by the factory.

  1. Calibration with software
    It should be easy to adjust the zero and full scale outputs for sensors connected to monitoring software. For example, software that controls a 4-20 mA sensor might have a 4 mA calibration setting and a 20 mA calibration setting. In this way, software control does what shunt calibration and previous calibration techniques do: it adjusts the sensor’s output, as well as controls the device’s reading of the output.

To calibrate a software-controlled sensor, follow these steps:

Connect the sensor to the control software
Accurately apply zero and full scale pressure to the sensor. (A minimum ±0.1% full scale accuracy of applied pressure is recommended.)
Using the software, adjust the zero and full scale output calibration variables until the corresponding output from the sensor is correct.

Pressure sensors are generally divided into two-wire, three-wire, four-wire, and some five-wire systems.

The two-wire system of the pressure sensor is relatively simple, and ordinary users know how to wire it. One is connected to the positive pole of the power supply, and the other wire is connected to the negative pole of the power supply through the meter. This is the simplest.

The three-wire pressure sensor is to add a line on the basis of the two-wire system. This line is directly connected to the negative pole of the power supply, which is more troublesome.

The four-wire pressure sensor has two power input terminals. The other two are signal output terminals. Most of the four-wire systems are voltage outputs. Instead of 4~20mA output. 4~20mA is called pressure transmitter, most of which are two-wire system.

The signal output portion of the pressure sensor is not amplified. The full-scale output is only tens of millivolts. Some sensors have an internal amplifier circuit, and the full-scale output is 0~2V.

For how to connect the display meter, it depends on the range of the meter. If there is a gear suitable for the output signal, you can measure it directly. Otherwise, you need to add a signal conditioning circuit. The five-wire pressure sensor is different from the four-wire type, and there are fewer five-wire pressure sensors on the market.

Read more about: What Is 0-10V Signal Output?

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Extended reading: Hydrostatic Pressure Transmitter

Sino-Inst offers over 20 air pressure transducers. A wide variety of air pressure transducer options are available to you. Such as free samples, paid samples. Sino-Instrument is a globally recognized manufacturer of air pressure transducers, located in China.

Sino-Inst sells through a mature distribution network that reaches all 30 countries worldwide. Air pressure transducer products are most popular in Europe, Southeast Asia, and Mid East. You can ensure product safety by selecting certified suppliers. With ISO9001, ISO14001 certification.

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About KimGuo11

Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects. Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.