How Does a Pressure Transmitter Work?



Introduction


The pressure transmitter is a device that transforms electric signals from the transducer into much larger electrical signals.


It is one of the most versatile instruments that is used in industries today. The pressure is the main value in control as well as instrumentation.


It can even be used to calculate different variables like flow and level.


There are multiple types of pressure transmitters available in the market for applications with varied requirements.

Difference Between a Transmitter and a Transducer?


Pressure transmitter and transducer are not interchangeable terms. Many people confuse a transmitter with a transducer. Let’s use understand in brief what these terms mean.


Transducer


It is a device that converts a form of energy into another. For instance, an electrical transducer converts temperature into analog electrical signal.


Transmitter

This is a machine that converts an electrical signal from a transducer into a larger electrical signal. This converted signal can be sent to a long distance to a DCS or a PLC.

Types of Pressure


There are multiple types of pressure and let’s understand each one in brief:


Absolute


This type of pressure transmitter uses a perfect vacuum as its reference which is 0 psi.


A perfect vacuum does not change, irrespective of the weather or the area. Removing the atmospheric aspect from your calculations can make your work simpler.


When it comes to industrial applications, you use absolute sensor everywhere there is vacuum, which is many.


Gauge


It is a form of differential pressure that uses atmospheric pressure as one of its points.


Gauge is one of the most common pressure measurements. Atmospheric conditions such as weather and altitude vary in different areas and will affect your sensor.


This is where you will have to consider geographic conditions and meteorology.


A gauge transmitter does not look the same as a DP. It has a single process connection since you will measure the atmosphere through the transmitter's vent. With the gauge transmitter, you can measure the pressure in a closed system.

Differential


You use this type of pressure transmitter to read the pressure difference between two points.


In applications such as a flow, this transmitter uses an orifice plate to create pressure change between two points.


After you have found the differential, you can calculate the flow with the K-factor of the basic element.

Working of a Pressure Transmitter


When the differential pressure transmitter system is installed, it includes three parts.


These are the pressure guiding tube, electrical signal cable and the differential pressure transmitter.


During the process, the pressure of the medium is transmitted through the isolating diaphragm and silicone oil to the central measuring diaphragm.


The pressure is received on the double-sided isolating diaphragm from the pressure guiding tube. The flexible sheet changes its formation with the pressure difference.


The displacement of the measuring diaphragm is positively proportional to the differential pressure.


As the diaphragm changes, the capacitance of the capacitor also changes. With this, the circuit converts it into a DC current signal of anywhere between 4 and 20 mA.

Frequently Asked Questions


What is the use of a pressure transmitter?


A pressure transmitter is used to measure the pressure of various forms like fluids, liquids and gasses in the industrial sector.


Other than just checking the pressure of equipment, they can be used for:


  • Flow measurement

  • Filtration system monitoring

  • Level measurement applications


How do you test a pressure transmitter?


Follow the below-mentioned steps to test a pressure transmitter:

  • Connect the positive terminal of the transmitter and the positive terminal of the power supply

  • Connect the negative terminal of the transmitter and the positive lead of the multimeter

  • Connect the negative lead of the multimeter and the negative terminal of the power supply


What is the difference between a pressure switch and a pressure transmitter?


Unlike a transmitter that translates all the pressure in its range, the switch will trigger at a particular set pressure.


The set pressure can be low or high and may also engage or disengage the circuit.

Conclusion


We hope to have helped you understand how a pressure transmitter works along with some basic information on the difference between a transmitter and a transducer and the different types of pressure.


If you have any questions, please drop them in the comments section and we will answer them at the earliest.

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