In A Process Plant it is often necessary to measure Pressure of Liquids, Gases and Vapor in Pipes and Closed Vessels. This Measured Pressure should be then sent to a PLC which is in a distant Control Room.
The PLC then uses this Pressure Value to Control the Process Plant.
Pressure Gauges or Pressure Sensors may be used to measure Pressure but they do not have a capability to transmit the measured pressure signal to a distance.
So an instrument called PRESSURE TRANSMITTER is used for this Purpose.
As the name indicates Pressure Transmitter is an instrument that is used for measuring pressure which is then converted into a Proportional Electrical Output signal. This Output Signal is then transmitted to a control system like PLC.
The Input of Pressure Transmitter is the Pressure to be measured and the Output Signal is usually a Voltage Signal of 1 to 5 Volt or a Current Signal of 4 to 20ma which represents 0 to 100 Percentage of the Measured Pressure.
Pressure Transmitter is a device that is composed of three fundamental components a PRESSURE SENSOR, a SIGNAL CONVERTER and a TRANSMITTER.
Pressure Transmitter first measures the Pressure of Liquids and Gases using its Pressure Sensor. The Pressure Sensor then converts this Pressure Value into an Electrical quantity.
The Signal coming directly from the Sensor is small, this small Signal would not be useful to us if we send it to a receiver.
So a Signal Converter is used to convert this Output of the Sensor into an Analogue Voltage of 1 to 5 Volt or Current Signal of 4 to 20ma that are easily transmittable.
Now the Transmitter Transmits these signals to its designated Receiver and displays the reading.
There are many types of Mechanical and Electrical Sensors available in the market.
All Pressure Sensors Sense the Pressure by measuring a physical change within the sensor. This physical Change can be Capacitance, Resistance Or Frequency.
Pressure Transmitters are of mainly three types
They are Gauge Pressure Transmitter,
Absolute Pressure Transmitter and
Differential Pressure Transmitter.
Every Pressure Transmitter Measures Pressure with respect to a particular Reference Pressure.
Knowing the Pressure that a Transmitter uses as its Reference is very important in selecting the type of Pressure Transmitter to be used in a Process.
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