Testing a knock sensor... seriously...

[Silent_NightR34]

Ok so I would like to test my knock sensor. I've read that they are piezoelectric devices and I happen to have a research project that deals with piezoelectric materials. I was wondering if I could use an impedance analyzer to determine whether or not my knock sensor is good or bad. If I do test it, is there anything I should look for? Would the capacitance be very low (broken ceramic material) or the loss factor be high (a short circuit)? The impedance analyzer I have access to is an Agilent 4294A. Thanks.

[1KleenS13]

You need a graphing meter or a regular DVOM set it to a 1 or 5 volt scale. Just tap on the block lightly with a hammer and look for fluctuation.

[Silent_NightR34]

So like an oscilloscope? If it doesn't fluctuate then I assume it's broken? Sorry for my lack of knowledge on knock sensors but do they have a 5v reference voltage or does it generate the induced voltage itself? My piezoelectric electric devices generate induced voltage but I'm not familiar with how these actually work...

[1KleenS13]

A oscilloscope will work great. I've seen some cars that had a 5 volt signal going ot them, but I dont know what the 240's have. You should see the frequency of the knock on the scope, if it doesnt do anything its shot, but also try KOEO to confirm it doesnt have the 5 volts running to it. Your knowledge is actually better than most.