Understanding the difference in what electronic pressure detectors referred to as sensors, transducers, or transmitters these three terms mean is important to ensure the chosen device is right for the end application. So how do you differentiate between them? Pressure sensor can be regarded as a generic description for any device that measures pressure and provides an appropriate output in response.
- 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.
- 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.
- Pressure transmitter
In contrast to a voltage-output transducer, a pressure transmitter has a low-impedance current output, most commonly designed to transmit analog 4-20mA signals. The output may be designed for use with either a 2-wire or 4-wire current loop. 4-20mA pressure transmitters provide good electrical noise immunity (EMI/RFI), making them ideal when the signal must be transmitted long distances.
Transducer Vs Transmitter
Pressure transducers and transmitters are categories of pressure sensors widely used in industrial application and process control applications and differ in their output characteristics.
- Lowest cost.
- Suitable where connection distances can be short and noise is not a problem.
- Needs stable bridge-excitation voltage.
- Less susceptible to noise.
- Shorter connection distances than pressure transmitter.
- Lower power consumption than pressure than transmitter.
- Can work with unregulated bridge-excitation voltage.
- Low power consumption.
- Easy to use in ubiquitous 4-20mA industrial sensing.
- Long communication distance.
- Low susceptibility to noise.
- Typically higher power consumption than transducer types.