Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Jonn1996 on 21/06/2014 16:33:55

Title: Testing the piezoelectric properties of Quartz Crystals
Post by: Jonn1996 on 21/06/2014 16:33:55
Hello :)

I am Jon and I am conducting an experiment with Quartz Crystals to test their piezoelectric properties. I wanted to ask you a question about my experiment set up.

Which type of force is required to be applied for voltage to be produced? Could I apply a compressive force with clamps on one end of the crystal, and wrap a long piece of copper wire on its other end so to measure the voltage produced.

Could you please advise me if I am carrying out the experiment correctly? What kind of a force do we have to apply to Quartz Crystals for a voltage to be produced?

Please advise me on my experiment set up.

Thank you very much!
Jon
Title: Re: Testing the piezoelectric properties of Quartz Crystals
Post by: Bored chemist on 21/06/2014 17:40:17
I think you need to connect the meter to the same part of the crystal that you are compressing.
That means you need something like a sandwich of plastic (to act as an insulator), aluminium foil, the crystal, foil, and plastic again.
Put the whole lot in a clamp and measure the voltage between the two bits of foil when you compress it.
Also, the electric charge will leak away very quickly, so you won't see a steady voltage, just a "spike".

You might find this interesting
http://vega.org.uk/video/programme/195

Title: Re: Testing the piezoelectric properties of Quartz Crystals
Post by: evan_au on 21/06/2014 23:12:38
There are many different ways that quartz crystals can generate electricity.

Crystals designed to produce electricity are cut in specific shapes (http://en.wikipedia.org/wiki/Crystal_oscillator#Crystal_structures_and_materials), parallel to specific planes within the crystal.

The bending force can be applied in several different directions (http://en.wikipedia.org/wiki/Crystal_oscillator#Operation), and the voltage can appear on different faces. So try placing the electrodes on different faces, and applying the force between different faces.

To measure the generated voltage, it is better to use a high-impedance measurement:

Another way to make a measurement may be to tap it repeatedly, such as with an electric toothbrush. This will be measurable on the AC scale of a meter - or you can get cheap Oscilloscope "Apps" for a smartphone, or free programs like "Audacity" for a PC.