Acquring signal from piezo sensor

[peterRFA]

im new to labview.im using usb-6251 to read voltage from a piezo sensor. i started off by reading the voltage with an avometer and it read 0 volts at free strain now i used a BNC cable to wire the piezo to the analog input channel and read it using the daq assistant there was on offset of about 1.7 volts when i used floating source configuration. when i used ground ref source configuration the readings were not reasonable it kept drifting while im not applying strain and whever i touch the insulator of the cable the reading keeps going from min voltage to max voltage. i made sure of the positive and negative terminals and that im reading from the correct channel.any help with the configuration or a possible reason for the problem would be appreciated . this is a screenshot of the readings while using floating source and no strain applied (it should be reading zero)

[NIquist]

An "AVOmeter"?!?  Haven't heard that term in... well actually ever.  But my dad used to have a "Megger" so I know what you mean.

It sounds like your electrical setup is probably wrong, not your DAQ.  What kind of piezo are you using?  What kind of signal conditioning circuit is conected to it and what signal does the circuit output???

EDIT:  Added avometer wiki-link.

[AnalogKid2DigitalMan]

You will probably need some sort of signal conditioning since the impedance of the piezo is probably fairly high. What you are detecting is probably ambient 50Hz EMF fields, as witnessed when you touch the cabling.

-AK2DM