What Does a Pressure Transducer Do?

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The terms pressure sensor, pressure transducer, and pressure transmitter are often used interchangeably. Is there a difference between the three pressure instruments? Yes and no.

Pressure Sensors, Transducers, Transmitters: What Are They?

Here’s a brief overview of these three types of pressure measurement instruments:

  •  Pressure sensor — A bare sensor that converts pressure into an unamplified electrical output signal, typically 2mV/V.
  • Pressure transducer — A pressure sensor mounted on a pressure connection with electrical connection, typically with an unamplified output signal.
  • Pressure transmitter — A transducer with an amplifier board and an amplified output signal, typically 4-20mA, 0-10V, or 0-5V.

Pressure transducers and transmitters are two types of pressure sensors, but not all pressure sensors have a transducer or transmitter. However, even though each of the three devices has as a slightly different function, some customers and manufacturers, including WIKA, use the terms interchangeably.

How Does a Pressure Sensor Work?

Pressure deforms the diaphragm of a pressure sensor. This deformation causes a change in the electrical characteristics of the circuit behind the diaphragm that is proportional to the pressure applied. Modern industrial pressure sensors, therefore, convert the physical variable “pressure” into an electrically quantifiable variable.

Deformations in electronic pressure sensors are extremely small – just a few microns – which gives them excellent dynamic characteristics. Low material strain makes them highly resistant to alternating loads and contributes to long-term durability.

There are several available technologies for pressure sensors. The table below includes the most common ones, as well as some of their characteristics.

Technology Pros Cons Most Common Uses
Ceramic thick Film
  • Low cost
  • Dry sensor
  • Requires seal
  • Multiple materials in wetted paths
  • Limited pressure range
  • Low-cost applications
  • Integrated as a bare sensor
  • High accuracy
  • Low pressure ranges available
  • Wet sensor
  • Low pressure applications (below 300 psi)
Thin film
  • Dry sensor
  • High pressure ranges available
  • All-welded design
  • Not available for low pressures
  • High pressure applications

What Is a Pressure Transducer?

One step up from a pressure sensor, a pressure transducer includes a sensor as well as a pressure connection and an electrical connection. Normally, thin-film pressure transducers have the sensor element welded to the pressure connection and then bonded electrically. Piezo-resistive pressure transducers, on the other hand, call for many more production steps as they require a diaphragm seal to protect the semiconductor sensor element from the process medium.

Typical output signals from pressure transducers are between 10 mV and 100mV, depending on the sensor type. These signals are not standardized, however, nor are they compensated.

How Do Pressure Transmitters Differ from Pressure Transducers?

Pressure transmitters go one step further by adding an amplifier board, making them ideal when sending signals a long distance. These pressure instruments can provide different types of output signals, including:

  • Millivoltage
  • Amplified voltage, 4-20mA, or both, such as with the A-10
  • Digital, such as with the MHC-1

Pressure transmitters are often used in process applications where they can be combined with various diaphragm seals. Most pressure transmitters also feature additional options. WIKA offers:

  • “Scale down,” “span reset,” or “turn down” calibration to reset measuring span over a large range
  •  Shifting of the zero point over a wide range
  • Calibration of the damping of the output signal between 0 and 32 seconds
  • Hart® smart transmitters with logging capabilities that can be calibrated, tested, and reset via the control desk or hand terminals

WIKA manufactures a variety of pressure transmitters, including units for:

  • General purposes, see the S-20
  • Hazardous areas, see the E-10
  • Submersible liquid level measurements, see the LS-10
  • Sanitary applications, see the SA-11 that meets 3A and EHEDG sanitary criteria
  • Special purposes, see the MH-3 for mobile working machines
  • Meters and displays, see the DI32-1 digital indicator with multifunction input

Still need more information? Let the experts at WIKA help you select the pressure sensor, pressure transducer, or pressure transmitter that your process needs. We can also modify standard instruments or design new ones to meet the requirements of your particular application.

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