Compressed air pressure sensors (also known as pressure transducers) are important sensors for industrial air compressors. They are used to verify that the compressed air supplied to equipment meets requirements, as well as to monitor for air leaks and maintain the integrity of pressurized piping. These sensors convert air pressure into 4–20 mA, 0–10 V, or RS485 signals, which are then processed by a compressor controller or a PLC (Programmable Logic Controller).
Typically, these sensors are installed at locations such as the compressor discharge outlet, air receiver tanks, and distribution manifolds to monitor pressures—commonly in the 0–10 bar or 0–16 bar (approximately 0–150 psi / 0–230 psi) range. The readings they provide directly determine when a compressor should load or unload.
In the following sections, we will examine where to install these sensors and transducers within a compressor system and its associated air distribution network, how to determine the appropriate measurement range for a 0–1 MPa pipeline, and key factors to verify before placing an order.
What is a Compressed Air Pressure Sensor?
Compressed air pressure sensors are specialized pressure sensors designed for use in air compressors and pneumatic systems. They convert measured compressed air pressure into digital or analog electronic signals, enabling the monitoring and control of high-pressure compressed air and gases. For heavy-duty applications, full-scale ranges typically fall between 100 and 1000 PSI.
In industrial air compressors, pressure sensors are used to measure and control:
- Inlet and outlet pressure
- Pressure drop across filters
- Cooling water inlet and outlet pressure
- Compressor oil pressure
These sensors play a critical role in maintaining the performance and efficiency of a compressor. For instance, a pressure sensor measures the air pressure within a storage tank, and this reading is used to control the starting and stopping of the compressor.
What is Compressed Air?
Compressed air is air that has been compressed by an external force. Air is compressible; an air compressor performs mechanical work on it, reducing its volume and increasing its pressure to produce compressed air.
In factories, compressed air serves as a vital power source. Compared to other forms of energy, it offers several distinct advantages:
- Clean and clear
- Easy to transport via pipelines to various points of use
- Resistant to overload: if a pneumatic tool is overloaded, it will simply stop rotating rather than burning out
- Capable of operating in many harsh environments
- Air itself is an inexhaustible resource
Sino-Inst has a wide variety of products. Below are some of our featured products. You can click on the pictures to learn more.
How Does a Compressed Air Pressure Transducer Work?
Common compressed air pressure sensors can be categorized by their operating principles as follows:
- Strain-gauge type: Measures pressure by utilizing the deformation of a material under load. A strain gauge is attached to an elastic element; as the element deforms under pressure, the resistance of the strain gauge changes. By measuring this change in resistance, the pressure can be calculated.
- Capacitive type: Measures pressure based on changes in capacitance between two conductive plates. Pressure variations alter the distance between the plates, which in turn changes the capacitance; the pressure is then determined by measuring this change in capacitance.
- Piezoelectric type: Relies on the fact that certain materials (such as quartz) generate an electric charge on their surface when subjected to pressure. Pressure is calculated by measuring the change in this charge. Piezoelectric sensors can only measure fluctuating (dynamic) pressure; they are suitable for analyzing pressure pulsations in piston-type air compressors but cannot be used to measure or control stable pressure within a piping network.
- Piezoresistive type: Utilizes the change in electrical resistance that occurs when a semiconductor material is subjected to pressure. The pressure is determined by measuring this change in resistance.
What are the Three Types of Pressure Transducers?
The pressure types mainly include gauge pressure, absolute pressure and differential pressure.
Pressure transmitters can be divided into the following types according to the measured pressure type:
Differential pressure transmitter:
The differential pressure transmitter measures the difference between two pressures. It is used to measure the liquid level, flow rate and pressure of liquids, gases or steam. Then the pressure is converted into a 4~20mA DC signal output.
Absolute pressure transmitter:
The absolute pressure transmitter measures pressure relative to a perfect vacuum. It is used for vacuum measurement and control. The absolute pressure transmitter completely solves the problem of difficult vacuum measurement.
Gauge pressure transmitter:
A gauge pressure transmitter is an instrument for measuring pressure. A gauge pressure transmitter is mainly used to convert a pressure signal into a standard electrical signal and output it to a control system or instrument.
In industrial production, it is often necessary to monitor and control the pressure of materials. A gauge pressure transmitter can provide a high-precision and high-stability pressure signal.
According to the working principle, pressure transmitters can be divided into seven categories. See 7 Types of Pressure Sensors: Different Types, Working Principles, and Definitions
Compressed Air Pressure Sensor Applications
Compressed air pressure transmitters are widely used in the petroleum, chemical, pharmaceutical and food industries, and are an essential part of industrial automation.
Sensors are commonly used for two types of pressure measurements:
(1) Determine if the compressed air output to the equipment is appropriate
(2) Monitor air pressure leaks for pressure line maintenance.
Sino-Inst’s compressed air pressure sensor customization case:
- Medium: compressed air
- Range: 0 to 16 bar
- Output: 4–20 mA
- Supply voltage: 24 V DC
- Operating temperature: up to 220 degrees Celsius
- Sampling frequency: 2000~3000Hz
- Response time: 0.2 ms
- Accuracy: 0.25% FS
- Process connection: 1/4 inch NPT
Where and How to Install Pressure Sensors on an Air Compressor
Common installation locations include:
- Compressor discharge port / unit outlet: For load/unload or variable-frequency control, and overpressure shutdown.
- Oil-air separator tank / oil circuit (in oil-injected screw compressors): For low oil pressure alarms.
- Air intake filter: For clogged filter element alarms.
- Filters and dryers (differential pressure): To signal the need for filter element replacement or to detect dryer malfunctions.
- Air receiver tank: For monitoring storage pressure and coordinating multiple air compressors.
- Main distribution piping / point of use: For monitoring supply pressure and detecting leaks.
However, there are two critical challenges to consider when installing sensors on an air compressor:
- Vibration: Air compressors generate significant vibration. Sensors mounted directly onto the compressor housing are subjected to this same intensity of vibration, which can easily lead to malfunctions unless the sensor is specifically designed for such harsh operating conditions.
- Temperature: The presence of moving parts combined with the compact internal space of the compressor housing leads to elevated temperatures. This can cause temperature-induced errors in the sensor’s output, which in turn results in inaccurate power calculations.
Compressed Air Pressure Sensor Order Guide
1. According to the type of pressure to be measured
The pressure types mainly include gauge pressure, absolute pressure, and differential pressure. Gauge pressure is measured relative to atmospheric pressure and can be above or below it.
Absolute pressure is measured from absolute zero pressure (a perfect vacuum).
Differential pressure refers to the difference between two pressures.
2. According to the measured pressure range
In general, the maximum working pressure should be no more than about two-thirds of the measurement range.
The maximum pressure of the system should be considered. Generally speaking, the maximum pressure range of the pressure transmitter should reach 1.5 times the maximum pressure of the system.
Some water pressure and process control have pressure spikes or continuous pulses. These spikes may reach 5 or even 10 times the “maximum” pressure, which may cause damage to the transmitter.
Continuous high-pressure pulses close to or above the transmitter’s maximum rated pressure will shorten its service life.
However, increasing the rated pressure of the transmitter will sacrifice the resolution of the transmitter. Snubbers can be used to damp the spikes, but they slow down the sensor’s response.
Check the datasheet for the number of pressure cycles the transmitter is rated to withstand without loss of performance.
3. According to the measured medium
Measured media include dry gas, gas-liquid mixtures, highly corrosive liquids, viscous liquids, and high-temperature gases and liquids.
Choosing the right transmitter for the medium extends its service life.
4. According to the maximum overload of the system
The maximum overload of the system should be less than the overload protection limit of the transmitter; otherwise, it will affect the service life of the transmitter or even damage the transmitter.
Usually, the safe overload pressure of a pressure transmitter is 1.5 to 2 times the full scale.
5. According to the required accuracy
Transmitters are graded by accuracy class, and each class has its own basic error limit (expressed as a percentage of full-scale output).
In practice, choose the accuracy class based on the measurement error your control system can accept and on cost.
6. According to the operating temperature range of the system
The temperature of the measuring medium should be within the operating temperature range of the transmitter. Operating above this range causes large measurement errors and shortens the transmitter’s service life.
During production, each transmitter is temperature-compensated so that the error caused by temperature stays within its accuracy class.
In high-temperature situations, you can consider choosing a high-temperature pressure transmitter. Install auxiliary cooling such as condensate coils (siphons) for steam, or cooling fins for hot gases.
7. According to the compatibility of the measuring medium and the contact material
Where the medium is corrosive, choose wetted materials compatible with it, or use a special surface treatment.
8. According to the pressure interface form
Flange connection, threaded connection, clamp connection and hose connection, etc.
9. According to the power supply and output signal
Usually, the pressure transmitter is powered by a DC power supply and provides a variety of output signal options, including 4~20mA DC, 0~5V DC, 1~5V DC, 0~10V DC, 0~10mA DC, etc., and can have RS232 or RS485 digital output.
10. According to the on-site working environment and other conditions
If there is vibration or electromagnetic interference on site, tell the supplier when selecting the model so it can be taken into account.
Sino-Inst offers many models of compressed air pressure sensors and can customize them to your requirements.
If you have any instrument-related questions, please contact us. Our professional engineers will customize a solution for you.
