Pressure Indicating Transmitter

Pressure indicating transmitter, abbreviated as PT and PIT, is an instrument for measuring, controlling and indicating positive, negative or differential pressures of different fluids.  Depending on the configuration, a pressure transmitter may output the gauge pressure or the absolute pressure.  Pressure indicating transmitters display the pressure the operator and convert the signal to be sent to an external destination.  Pressure transmitters do not contain a local display.

features and functions of a Pressure Indicating Transmitter

• Pressure Measurement  -  The primary function of a pressure indicating transmitter is to measure the pressure of a fluid, gas, or vapor within a system.  It utilizes pressure sensing elements such as diaphragms, Bourdon tubes, piezoelectric crystals, or strain gauges to detect changes in pressure.
• Display  -  Unlike traditional pressure transmitters, which only provide output signals, pressure indicating transmitters feature built-in displays.  These displays show the measured pressure in units such as psi, bar, Pascal, or other pressure units depending on the application.
• Output Signal  -  In addition to displaying the pressure locally, pressure indicating transmitters also provide output signals that can be transmitted to other devices or systems for monitoring and control purposes.  Common output signals include analog signals, digital signals, or voltage signals.
• Accuracy and Range  -  Pressure indicating transmitters are available in various pressure ranges and accuracy levels to suit different applications.  The range and accuracy of the transmitter should be selected based on the specific requirements of the application and the expected pressure range.
• Process Connection  -  Pressure indicating transmitters feature process connections that allow them to be connected directly to the system or pipeline where pressure measurement is required.  The selection of the process connection depends on factors such as system pressure, temperature, and compatibility with the process fluid.
• Temperature Compensation  -  Many pressure indicating transmitters incorporate temperature compensation features to ensure accurate measurements over a wide range of operating temperatures.  Temperature variations can affect the performance of the sensor, and temperature compensation helps maintain measurement accuracy.
• Applications  -  Pressure indicating transmitters find applications in various industries, including oil and gas, petrochemical, chemical processing, HVAC, water and wastewater treatment, and manufacturing processes.  They are used for monitoring and controlling pressure in pipelines, tanks, vessels, pumps, compressors, and other equipment.

Input/Output

Inputs:  Pressure transmitters can be loop powered or externally powered.  Typically the AC voltages are 120 volts or below.  DC voltages range as high as 42 VDC.

Outputs:  Output can be 4-20mA, Fieldbus, DeviceNet or mV.

Depending on the process, it can be mounted directly to the process or remotely mounted.  Remote connections can be mounted on a DIN rail or on a pipe for indication.  Some pressure transmitters have a built in pressure sensor and some require a separate sensor.

Connections

Process connections are typically made of several different materials.  316L SST, Hastelloy, Monel.  When using a pressure transmitter, it should be mounted on a manifold valve to allow the transmitter to be removed while it is in service. 

Technology

New, high end pressure transmitters allow you to customize performance, functionality, diagnostics, and connection systems depending on your application.  Other transmitters have the ability to output the signal directly into your companies intranet or internet.  Wireless transmitters such as those in the PlantWeb family are being utilized more frequently in plant applications where it is cost prohibitive to run wire and communications cable.

Testing

Some of the more accurate pressure transmitters are used in hydrotest applications.  The 4-20 mA signal may be conditioned and data points stored directly within the transmitter or they may output the signal into an external data logger.