
Pressure Sensors, Transmitters & Gauges

Pressure sensors, transmitters, and gauges are critical devices in various industrial applications that require precise measurements of pressure.
Pressure sensors are devices that sense and convert pressure into an analog or digital output signal. They can measure different types of pressure - gauge pressure, differential pressure, or absolute pressure.
Gauge pressure sensors measure the pressure relative to atmospheric pressure. For example, a tire's pressure is a gauge pressure since it's measured with respect to the ambient pressure. On the other hand, absolute pressure sensors measure the pressure relative to a perfect vacuum.
Differential pressure sensors measure the difference in pressure between two points. This measurement is crucial in various industrial applications such as flow measurement or monitoring filtration systems.
Pressure transmitters are essentially pressure sensors, but with an additional function. They not only measure pressure but also convert this measurement into an electrical signal for communication or control purposes. These signals, which can be analog or digital, are then used for process control or monitoring.
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More Information about Pressure Sensors, Transmitters and Gauges
Pressure transducers, similar to pressure transmitters, convert pressure into an electrical signal. The terms 'transmitter' and 'transducer' are often used interchangeably, but in some contexts, transmitters might refer to devices with more sophisticated signal conditioning and transmission capabilities.
Pressure gauges, whether mechanical or digital, provide a visual display of the pressure measurement. Mechanical pressure gauges use a bourdon tube or other mechanical sensing element that changes shape under pressure, driving a pointer on a scale. Digital pressure gauges, on the other hand, use electronic sensors and provide a digital readout, often offering higher accuracy, temperature compensation for precise measurements, and other advanced features.
Strain gauge technology is often used in pressure sensors. A strain gauge is a device that changes its electrical resistance when exposed to pressure. When this is calibrated to known pressures, it can provide very precise measurements.
Pressure switches are another important type of pressure device. They function to open or close an electrical circuit when a certain pressure is reached.
The selection of a pressure sensor, transmitter, or gauge depends on various factors such as the pressure range, high or low pressures, required accuracy, long term stability, whether the device will be exposed to challenging environments, and the ease of installation.
Instrumentation: Elements & Transmitters
2 pieces of hardware used in modern day instrumentation: measuring elements and transmitters.
Measuring Elements
Measuring elements are the part of the device that performs the measurement. For example, the measuring element of a pressure transducer is the part that is actually lowered into a tank that will take a pressure measurement. The measuring element of a flow meter is the part that actually measures the flow and an RTD or thermocouple takes the temperature measurement.
Transmitters
Transmitters collect information from measuring elements and sends the information to where it is needed. The transmitter interfaces with the measuring element and interprets the information. It then sends that information to a PLC, RTU or some other type of control unit. In many cases, the transmitter has the ability to communicate the information via multiple communication protocols. This may be necessary when the measuring element does not send the same type of signal that is needed by the controller. For example, it may be necessary to convert a temperature reading from a thermocouple to a 420 milliamp signal that can be received by a local PLC.