What is a Pressure Sensor?

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Today, we will hopefully cover all of the questions you may have about pressure sensors.

To understand pressure sensors, first, you need to understand the pressure. Pressure is an expression of force exerted on a surface per unit area.

We commonly measure the pressure of liquids, air, and other gases, amongst other things. The standard unit for pressure is the “Pascal”. This is equivalent to one “Newton per meter squared”.

A pressure sensor simply monitors this pressure and can display it in one of the several units known around the world. This is commonly the “Pascal”, “Bar”, and “PSI” or pounds per square inch in the United States.

The pressure of the air in your tire is a great example of pressure and how it is measured. As we air the tire up, the force it exerts on the tire increases, causing the tire to inflate. This is monitored with a pressure sensor inside the tire on newer vehicles.

So how does a pressure sensor work?

In a nutshell, it converts the pressure to a small electrical signal that is transmitted and displayed.

These are also commonly called pressure transmitters because of this. Two common signals that are used is a 4 to 20 milliamps signal and a 0 to 5 Volts signal.

Most pressure sensors work off of the piezoelectric effect. This is when a material creates an electric charge in response to stress.

This stress is usually pressure but can be twisting, bending, or vibrations. The pressure sensor detects the pressure and can determine the amount of pressure by measuring the electric charge.

Pressure sensors need to be calibrated so it knows what voltage or milliamp signal corresponds to what pressure. This is a basic “Zero” and “Span” calibration or minimum and maximum which is a common job for maintenance personnel.

In the RealPars video “What is Sensor Calibration and Why is it Important?” we described the sensor calibration in detail.

What are some of the common types of pressure that you can measure with a pressure sensor?
There are three common types that we use in the industry. First being “Gauge Pressure”.

This is measured in reference to atmospheric pressure which is typically 14.7 PSI. You will show a “positive” pressure when it is above atmospheric pressure and a “negative” when it is below atmospheric pressure.

The next type is “Absolute Pressure”. Simply put, this is the pressure as measured against absolute vacuum. A full vacuum will have an absolute pressure of 0 PSIa and increase from there.

If you need to read a pressure that is lower than atmospheric pressure, this is the type of sensor you would use.
The last type that is commonly monitored in the industry is “Differential pressure”.

This is exactly what it sounds like, the difference between two pressures, a pressure being measured and a reference pressure.

In industry, pressure sensors are used for a wide variety of processes. Some common uses are to measure the pressure of steam.

Steam is commonly used to heat many processes in manufacturing facilities. This pressure sensor on the steam system can serve multiple purposes though. First and most obvious is to observe and monitor the pressure.

Another purpose is to control when and where steam can flow and regulate its pressure. Steam can build up pressure in a vessel and become dangerous.

We can use the pressure sensor as an input device to open and close a control valve to keep the pressure and steam flow regulated. This only requires simple programming in the PLC to achieve this.

Pressure sensors are also installed next to filters in many industrial processes. If the filter begins to clog, the flow will decrease. As the flow of the liquid decreases, pressure can increase or decrease depending on which side of the filter is monitored.

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What is Sensor Calibration and Why is it Important?

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[ejimajiambrose]

Thanks RealPars team, you are the best. you have immensely contributed in enhancing my Instrumentation and Control skills. Keep it up.

[saitamasaitamas]

The Best Man....i learned a lot on this Channel...

[justengineering]

Very informative video. From the scratch, what is Pressure sensor, how does it work and what are types of Pressure sensors, all this is explained very well with the creative diagrams. Very useful for the students who are studying industrial automation.

A Pressure sensor is a device that catches the pressure and manages to change it into an electronic signal where the quantity depends upon how much pressure appealed.


Keep sharing such videos. Thank you.

[hubert]

Awesome video, just had a related issue at our plant.


Our feed-water tank, for the boiler, has a DP sensor that determines the water level. The lower port was clogged causing a false high reading in the feed-water tank. We never got makeup water, and the boilers tripped. All that rust build up at the bottom of the tank clogged our reading!


Now we have a blow down installed, to keep those ports clean.


Keep up the awesome work, I'm learning more every day!

[vishalhajare]

Hello Realpars, you are doing great job.... I'm mechanical engineer and have less knowledge of electronics components. But by watching your videos it would be easy to understand the mechatronic systems

[derina.maleek]

Realpars is a bright star in automation technology and our best resource for learning (thank realpars)

[sduduzomncube]

@Realpars thank you very much for the explanation, I am doing Internship at Endress Hauser so lot of things are clear now

[vannrodriguez]

thank you so much #RealPars for all of your very informative videos, , , even i didn't finished my engineering course, your videos was helps me a lot and then i applied it from actual at work.. more power to you RealPars, , .
merry christmas and a happy new year to all the staff of RelPars..

[mostafafaramin]

Thanx RealPars for creating and sharing these useful videos

[LeonardoLeo-jwdx]

I have been thinking about this for so long and I need a good answer, when do we use a pressure switch and when do we use a pressure transmitter?

[mouizimran]

Hi Realpars team,
Great work.. thanks a lot for your educational videos. They are quite clear to understand.
One request kindly make videos on the electronics used inside instruments.

[thassioam]

Thank you so much. All videos are just perfect, I can’t imagine how it could be better. Keep doing, congrats!

[souvikpal]

very informative video..please bring a video on bin level sensors...

[stevenlee]

Good video.It's useful for novice

[VideoHoctiengAnh-ohfq]

Great video, it's really helpful for me, thanks.

[marcfruchtman]

Very good video. I believe that the typical voltage range would normally be 1 to 5 volts, not 0 to 5 volts because we always want some minimal signal right?

[happygill]

Thanks for the video sir. Its very usefull to me.

[abdelkabirnfaoui]

Realpars, very very very professional explication and working . and all this vedio is just sam of big structure knowledge .thank you all for your hard work. i recommend to buying cours

[IsaiasSantos-gsdv]

Your videos are very explanatory and take many doubts, you could by subtitles in Portuguese, because I have difficulties with English, I already thank you

[HassanSahm]

What is the equation to determine the level of the liquid with size and gravity ?
Thank you