How do I read analog devices that produce relatively high voltage?
Piezo vibration sensors produce a high voltage, but very low current.  Further, you are generally interested in sensing only a few things - level of vibration, frequency, amplitude, shocks, etc.

So the interface will depend greatly on what you want to sense.  Assuming you only want to know one or more of the following, then the interface suggested below will work.


A vibration event such as a shock or sudden G force
The vibration level


The general interface is to push the signal through a diode, then a resistor into a capacitor that's attached to ground.  In parallel with the capacitor is a clamping diode that limits the voltage spikes to a more reasonable voltage (5V, for instance).

Now each time a spike happens, the capacitor will charge a little bit.  If you have continuous vibration it will charge more quickly.  It'll eventually reach the level of the clamping diode as long as the vibration exceeds the capacitor's self discharge rate.

Sense the voltage on the capacitor, and you'll learn about the signal coming in.

If you put a resistor in parallel with the capacitor then you can define how quickly the capacitor discharges.  A small resistor will discharge quickly, and you can count how often the piezo is hit or dropped.  A large resistor will allow the charge to build up so you won't see individual events, but instead get a higher voltage with more vigorous vibration, a lower voltage with less vibration, and no voltage with no vibration.

If you need more information than this simple technique, then you'll want to use a signal transformer to bring the signal down into the 5V range, and a precision op-amp and ADC.