Arduino analog input protection I've been trying to find a way to protect my analog input pins (for my Leonardo and Pro micro). I'm basically using them to read an amplified piezo sensor output. The output is amplified because I'm using it to measure very low signal (heartbeats). The normal level of the sensor's output doesn't exceed 5V when I'm measuring heartbeats or chest movement, yet when the sensor is moved rapidly or lifted, I can expect a 5v+ voltage. I know that Arduino has an internal protection circuit, will that be enough to combat those sudden movements? 
If not, I've read so many posts on this topic including this one:
http://www.thebox.myzen.co.uk/Tutorial/Protection.html

If I wanted to add a series resistor by itself as a protection will it be okay? and also, my signal is already small, wouldn't adding a resistor attenuate it even more? 

Most circuits seem to have a capacitor, my signal is DC shifted upward (to avoid -ve voltage), wouldn't the capacitor remove that offset?

Finally, if I wanted to use the diode clamping diodes, which diodes should I use (i.e 1n4148 or 1n4002)?

Thank you
If you amplified with an op-amp powered by 5V then it couldn't produce more than 5V output, so that could be your solution. Failing that, I think a resistor and a couple of clamping diodes would help. The resistor is to current-limit the clamping diodes. I don't think you need to worry about dropping the voltage through the resistor because the analog input is high impedance.

I think the 1n4148 would be OK, I don't see why not.