Almost everyone uses the terms “pressure transducer” and “pressure transmitter” interchangeably, but the two devices are technically not the same. A pressure transducer converts pressure to an electronic signal, while a pressure transmitter also amplifies, modifies, and sends that signal. Regardless of those differences, what’s important is to have the right output signal.
Many manufacturers and users do not differentiate between pressure transducers and pressure transmitters. However, these two types of pressure instruments are not technically the same.
Basically, a transducer measures pressure, load, force, or other states, and converts the reading into an electronic signal. A transmitter also converts a reading into an electronic signal, but it then amplifies, modifies, and sends that signal to a receiver.
Comparing Pressure Transducers and Transmitters
In a pressure transducer, a thin-film or piezo-resistive pressure sensor is mounted on a process connection. The transducer converts pressure into an analog electronic output signal, typically as a millivolt per volt output. These signals are not linearized or temperature compensated.
A pressure transmitter has additional circuitry that linearizes, compensates, and amplifies the signal from a transducer. The different signal types are typically voltage signals (e.g., 0 to 5 or 0 to 10 volts), milliamp (e.g., 4 to 20 milliamp), or digital. The instrument then can transmit the signal to a remote receiver.
Many pressure transmitters offer a variety of calibration options, including turndown and zero/span adjustment. Smart transmitters can be calibrated, tested, and reset remotely using a bus network.
Pressure Transducer or Transmitter: Which One to Choose?
Despite the differences between the two types of instruments, it really doesn’t matter what people call it or which one they use. What’s more important is whether the device suits a particular application and offers the needed output. Accuracy, range, working temperature, and the medium are all determining factors when selecting the right pressure instrument for an application.
As for the output signal, here are some factors to take into account:
- Typical mV outputs do not have temperature characterization.
- A current signal is more immune to interference and noise than a voltage signal.
- A current signal can also travel farther.
- An analog signal is just the pressure reading.
- A digital signal allows a user to collect more information and other variables besides pressure.
- The input card of many control systems accepts only amplified signals.
The bottom line: Get the pressure device you need, regardless of what it’s called. For expert advice on the best sensors to use with your particular application, contact the pressure measurement professionals at WIKA USA.