How Pressure Transducers Work: Principle, Types & Applications
” Pressure Transducer is a type of sensor which converts pressure into an Electrical signal such as ‘voltage’ or ‘current’ as per according to the change in pressure. Further we can use that electrical signal to get an alarm or to control an output. “
Working of pressure transducer
There are different types of pressure transducer with different shapes & sizes. In this post, We will explain one of the pressure transducer with metallic diaphragm.
This metallic diaphragm transducer contains a fluid behind the diaphragm. Due to process pressure on diaphragm, Filled fluid moves behind the diaphragm which in turn produces a pressure on electronic strain gauge. Finally Stain gauge produces the electrical signal proportional to the applied pressure.
Block Diagram of pressure transmitter
For better standing, We are explaining pressure transducer CerabarPMP135 by Endress+hausser. This 2 wired pressur sensor produces an analog output as an input to the PLC.
Pressure transducer CerabarPMP135 by Endress+hausser ; Diaphragm shown in an image left While complete sensor in right one
Features of pressure transducer Cerabar pmp135
Compact Size
Hygienic & flush mount metal sensors
Fully welded process connections
Suitable of SIP & CIP Cleaning
Easy & time Saving installation
Accurate measurement
Standard 4-20mA output
Easy PLC integration
Technical specifications of pressure transducer Cerabar pmp 135
Ingress Protection : 68
Process Temperature range : -10°C to 100°C ; +135°C (for one hour maximum)
Operating voltage : 12Vdc to 30Vdc
Current : 4 to 20mA
Pressure Range: 0 to 4 bar
Terminals of pressure transducer Cerabar pmp135
This sensor is 2 wired in which one wire is DC positive & another second wire is negative which produces a milli amps current output.
Electrical Signal from the sensor connected as an analog input to the PLC. In PLC programming, We need to set the range of analog input current in along with pressure range. PLC automatically calculate the pressure in proportional to the analog current.
Since its current range is 4 to 20mA & pressure range is 0 to 4 bar. At 0 bar, current 4 mA flows while at 4 bar pressure, 20mA current flows. PLC automatically calculates the pressure according to flowing current of the sensor.
M12 plug Terminals | Cerabar PMP135 by E+H
M12 plug Terminals | Cerabar PMP135 by E+H
Working explanation through a GIF (Cerabar PMP135)
A GIF attached below shows the working of pressure transducer connected across PLC . In which pressure transducer, Vacuum pump are connected across PLC. According to feed parameter of pressure, PLC produces a signal to vacuum pump to achieve the desired pressure & when that pressure is achieved, PLC disconnects the vacuum pump. Meanwhile, Pressure transducer continuously produces a milli amps signal to PLC to narrate the current pressure inside the chamber.
A GIF shows working of pressure transducer connected across PLC
Applications of Pressure Transducers
Water treatment plants
Boiler and steam systems
Hydraulic and pneumatic systems
Oil & gas industry
Vacuum systems
Process industries (food, pharma)
Frequently Asked Questions (FAQs)
1. What is a pressure transducer?
A pressure transducer is a device that converts applied pressure into an electrical signal such as 4–20 mA or 0–10 V. It is widely used in industrial automation systems to measure and monitor pressure accurately.
2. What is the working principle of a pressure transducer?
A pressure transducer works using a diaphragm and sensing element (usually a strain gauge). When pressure is applied:
The diaphragm deforms.
The strain gauge senses the deformation.
The internal circuit converts it into an electrical signal proportional to pressure.
For example, in a 0–4 bar range transducer:
4 mA = 0 bar
20 mA = 4 bar
3. What is the difference between a pressure sensor and a pressure transducer?
A pressure sensor detects pressure changes. A pressure transducer converts that detected pressure into a standardized electrical output signal (like 4–20 mA) that can be used by PLCs and control systems.
In simple words: Sensor detects → Transducer converts.
4. Why is 4–20 mA output commonly used?
4–20 mA is used because:
It is less affected by electrical noise.
It can transmit signals over long distances.
4 mA represents live zero (helps detect wire break).
It is the industrial standard in automation systems.
5. How do you connect a pressure transducer to a PLC?
Most industrial pressure transducers are connected to a PLC analog input module.
Basic connection:
+24V DC supply to transducer
Output (4–20 mA) to PLC analog input
Common/ground connected properly
The PLC then scales the current signal into pressure values.
6. What are the different types of pressure transducers?
Common types include:
Strain gauge pressure transducer
Capacitive pressure transducer
Piezoelectric pressure transducer
Absolute pressure transducer
Differential pressure transducer
Each type is selected based on application requirements.
7. Where are pressure transducers used?
Pressure transducers are used in:
Water treatment plants
Boilers and steam systems
Hydraulic and pneumatic systems
Oil and gas industry
Process industries (food, pharma, chemical)
They are essential for pressure monitoring and control.
8. What happens if a pressure transducer fails?
If a pressure transducer fails:
PLC may show 0 mA or below 4 mA (wire break indication)
Pressure reading may become unstable
Process control may stop or generate alarms
Regular calibration and proper wiring help avoid failure issues.
9. How do you calibrate a pressure transducer?
Calibration is done using a standard pressure source and a calibrated pressure gauge.
Steps:
Apply known pressure values.
Compare output signal (mA or voltage).
Adjust zero and span if required.
Calibration ensures accurate measurement.
10. What is the typical pressure range of industrial pressure ?
Industrial pressure transducers are available in different ranges, such as:
0–1 bar
0–4 bar
0–10 bar
0–100 bar
SUMMARY
A pressure transducer is a sensor that converts pressure into an electrical signal, like voltage or current, enabling alarms or output control.
This post focuses on the Cerabar PMP135 model by Endress+Hauser, featuring a metallic diaphragm and fluid behind it. The diaphragm’s pressure moves fluid to produce pressure on an electronic strain gauge, generating an electrical signal proportional to the pressure.
The Cerabar PMP135 is compact, hygienic, and offers easy installation and high ingress protection. It operates within a temperature range of -10°C to 100°C and uses a 4-20 mA current output for PLC input, effectively monitoring pressure in real-time.
Hope, You like the post. If you have any doubt, Suggestion or query Please do comments !
