How Do Piezoresistive Pressure Sensors Work?

Video Transcript

"Hi I'm Steve Jones and we are going to look at piezoresistive crystals. Now piezoresistive crystals are special, very special crystals and very expensive material but they're only very small. The huge advantage of them is that by applying pressure and twisting or bending them you find that you will get a voltage generated across the sides of the crystal. Now this will relate to the amount of bending. It also means you can actually use it to generate current sometimes and if you had a device which lights your gas cooker you might find that you have one of these that you press, it's piezo-electric and it produces electricity by distorting a piezo crystal. Now in general these are used quite widely particularly looking at for example a bridge. If you have a bridge and you want to see if it's going to distort or what kind of pressure is on the bridge, you actually take a crystal like this, you glue it firmly to the side of the component you want to see whether it stresses and taking the actual resistance of this crystal it will give you a measure of how much distortion there is to the bridge at that point. So piezoelectric, piezoresistive crystals are extremely useful for detecting deformations in major structures. In fact architects probably are the greatest users of these particularly bridge builders so that is basically how a resistive crystal system works."