checking piezo's

[brodave2]

I tested 20 piezo's this morning. I didn't find any with incorrect polarity, but I did find 4 that didn't work at all, or were not as loud as the others. To test them, I downloaded the free version of TrueRTA http://www.trueaudio.com/
It has a sine wave generator included. I ran a sine wave at 2.5khz and connected my test cables to the headphone jack on the mixer I have connected to my computer via a tascam us122 usb sound interface. I suspect you could drive them with your computer sound card headphone jack. I am not responsible if it burns out your headphone amp, I don't know what yours will handle. You connect the leads to the first one, then face it right at you, put another one parallel with it (right up next to it) and connect the second set of test leads to it. If the polarity is correct, when you connect the second one, the test tone will get noticeably louder. You can connect one with the polarity reversed to see what that does, just so you can see the difference. It doesn't get any louder.