Views: 17 Author: Site Editor Publish Time: 2022-04-19 Origin: Site
Piezoelectricity was first discovered in 1880 by Jacques and Pierre Curie. While experimenting with a variety of crystals, they discovered that applying mechanical pressure to specific piezo element like quartz released an electrical charge. It wasn’t until World War I when piezoelectric element was used for practical applications in sonar. Today, piezoelectric element is used everywhere that asking Google for directions to a new restaurant uses piezoelectric element in the microphone. However, if the piezo element does not make sound, how can we check whether piezo element is good or not?
What are the types of materials used in piezo elements?
What is the working principal of piezo elements?
How to check piezo element?
1. Inorganic piezoelectric materials are divided into piezoelectric crystals and piezoelectric ceramics. Piezoelectric crystals generally refer to piezoelectric single crystals, while piezoelectric ceramics generally refer to piezoelectric polycrystals. Piezoelectric ceramics are polycrystals that are formed by mixing and sintering the necessary ingredients with raw materials at a high temperature, and the fine crystal grains obtained by the solid-phase reaction between the powder particles and the sintering process are randomly assembled.
2. Organic piezoelectric materials, also known as piezoelectric polymers, such as PVDF and other organic piezoelectric film materials. This kind of material has the advantages of flexibility, low density, low impedance and high voltage constant, which is developing rapidly. It has been applied in water depth ultrasonic measurement, pressure sensing and ignition and detonation.
3. Composite piezoelectric materials, which is formed by embedding sheet, rod, rod, or powder piezoelectric materials in an organic polymer base material. It is widely used in underwater acoustics, electroacoustics, ultrasound, medicine and other fields.
Although we have specific materials suitable for piezoelectric elements, how does it work precisely? Piezo elements work with piezoelectric effect, whose most unique feature is that it can work in two ways. You can apply mechanical energy or electrical energy to the same piezoelectric material and get the opposite result.
Applying mechanical energy to the piezo element is called the direct piezoelectric effect. The piezoelectric element is placed between two metal plates. At this point, the material is in perfect balance and does not conduct current. Then, mechanical pressure is applied to the piezo element through the metal plate, which forces the charge in the piezo element to lose balance. Excessive negative and positive charges appear on opposite sides of the piezo element’s surface. The metal plate collects these charges, which can be used to generate voltage and send current through the circuit.
You can also perform the reverse operation and apply the electrical signal to the piezo element as an inverse piezoelectric effect. In the same situation as the above example, we placed a piezoelectric element between two metal plates. The piezo element’s structure is perfectly balanced. Then electrical energy is applied to the piezo element, which causes the structure of the piezo element to shrink and expand. As the piezo element’s structure expands and contracts, it converts the received electrical energy and releases mechanical energy in the form of sound waves. The inverse piezoelectric effect can be used in a variety of applications. Take a speaker as an example. The speaker applies a voltage to a piezoelectric element to cause the material to vibrate the air in the form of sound waves.
Set the range switch of the multimeter to the DC voltage of 2.5V, gently pinch the two sides of the piezoelectric element with the thumb and index finger of the left hand, hold the test lead of the multimeter in the right hand, connect the red test pen to the metal sheet, and place the black test pen horizontally on the surface of piezo element.
Then left hand press a little harder and then loosen it again, so that two voltage signals with opposite polarities are generated on the piezoelectric element, so that the pointer of the multimeter first swings to the right, then returns to zero, and then swings to the left with a swing amplitude of about 0.1 -0.15V. The larger the swing, the higher the sensitivity. If the pointer of the multimeter is still, it means the piezo element has electric leakage or is damaged. However, remember not to pinch the piezoelectric element with wet hands. The multimeter cannot be blocked with AC voltage during the test, otherwise the pointer will not be observed to swing, and it is best to use the R×l0k block before the test, and the insulation resistance should be infinite.
The other method is to use the R×10k block to measure the two-pole resistance, which should be infinite when normal, and then tap the piezo element lightly, with the pointer swinging slightly.
Learning something about piezo elements can help you know the materials that can be used in piezo elements and how to check piezo elements. If you want to buy high-quality piezo elements with reasonable price, Kailitech Company can provide you with the best products, as well as other piezo buzzers.