Introduction to Pressure Sensors, Piezoelectric Sensors and Pressure Transmitters

The terms pressure transducer, piezoelectric transducer, and pressure transmitter are often used interchangeably, and the exact definitions may vary from source to source. The following are general definitions. A pressure transducer is typically a millivolt output signal, a transducer has an amplified voltage output, and a transmitter provides a 4-20 mA output signal.

The terms pressure transducer, piezoelectric transducer, and pressure transmitter are interchangeable in some cases in industry. A pressure transducer can be described by a 4-20mA output signal, while a piezoelectric transducer is described by a millivolt level signal. Once the relevant details are described to define the output signal and the application, the correct terminology can be determined. Below is a quick guide to introduce each term and its advantages and limitations.

Pressure Transducers

A pressure transducer is typically a millivolt (mV) output signal (also a common term for all pressure types); a device that measures pressure. A millivolt output signal can typically be used at distances of ten to twenty feet from electronic equipment without significant signal loss. The signal is proportional to the power supply. A 5VDC power supply with a 10mV/V output signal can produce an output signal of 0-50mV. Older technologies such as bonded foil strain gauge or thin film technology can produce 2-3mV/V (mV/V) output signals, while MEMS technology can reliably produce 20mV/V output signals. The millivolt output signal gives design engineers the flexibility to tailor the output signal to the needs of the system and allows for reduced package size and cost.

Piezoelectric transducer

Piezoelectric transducer are typically high level voltage or frequency output signals, including 0.5 to 4.5V ratios (output signal proportional to power supply), 1-5V and 1-6kHz. these output signals should be used within twenty feet of the electronics. Voltage output signals can provide low power consumption for remote battery-powered equipment such as wellhead SCADA systems. Older voltage output signals such as 0-5V do not have the "non-zero minimum output" feature of a signal present when the sensor is at zero pressure, except for the 0.5-4.5V output which requires a 5VDC regulated power supply, typically 8-28VDC. The risk is that the system cannot distinguish between a sensor failure with no output and zero pressure.

Pressure Transmitters

Pressure transmitters are typically current output signals, i.e. 4-20mA, where the device measures current rather than voltage; most pressure transmitters are two-wire devices. 4-20mA pressure transmitters provide good immunity to electromagnetic interference (EMI/RFI) and require an 8-28VDC power supply. Because the signal is generating current, more battery life is consumed if operating under full pressure conditions.

Pressure Sensors are typically millivolt (mV) output signals (also a common term for all pressure types); devices that measure pressure. A millivolt output signal can typically be used at distances of ten to twenty feet from electronic "/a" equipment without significant signal loss. The signal is proportional to the power supply "/a". A 5VDC power supply with a 10mV/V output signal can produce an output signal of 0-50mV. Older technologies such as bonded foil strain gauge or thin film technology can produce 2-3mV/V (mV/V) output signals, while MEMS technology can reliably produce 20mV/V output signals.

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