Piezo Sensor Voltage Problems- DAQ

Hello,

I am trying to set up a piezo sensor (e.g. Maplin YU82D) with Labview (USB 6251) but am having some problems.

When nothing is hitting the piezo, there is usually a constant output of -10.5V and sometimes 10.5V. When the piezo is struck, a jump in voltage is seen, but this doesn't always drop back to the same level.

I am unsure how to solve the problems. I have looked through the forum and seen others having similar problems but am still unsure what to do. Any help would be greatly appreciated. Something tells me I need to add in some resistors.

(All my set up contains is a piezo with the positive going into an analogue input and the negative going into an analogue ground. I have tested with a multimeter and get sensible readings.)

Thanks in advance.