My output voltage is not stable while using DAQ and AE sensor

[elahetal]

HelloGuys,

I use "physical accoustic groups R15" as an AE sensor with "USB6251 DAQ" to sense the acoustic esmission of a sound wave



Everything goes well, for example when I apply a tap  to the sensor, I can see the correct output but the problem is that the output is not stable, even when I have no input, the output voltage changes slowly toward -10 or +10 although it shoud oscillate around zero.

Thanks for your help,

Ela

[AnalogKid2DigitalMan]

Do you have the sensor ground connected to the Analog Input ground?

-AK2DM

[elahetal]

YES

[AnalogKid2DigitalMan]

Does the sensor use an amplifier or have one built in?

Can you attach a manual or spec sheet for the sensor (an amplfier if required)?

A quick description of how you have it all wired up, including pin #'s of the DAQ card.

-AK2DM

[elahetal]

I attached the datasheet for R15a but I use R15 both are the same.

There is no built in amp, and I have not used the preamp.

I have used the bnc cable to connect the sensor to one of the analog input pins and connect its ground to the DAQ ground.

Thanks for following up my problem.

[elahetal]

I have used pins # 1 & 3

about built-in amp, I'm not sure. We had that sensor in lab from years ago and I used it. The datasheet doesnot provide enough info.

[AnalogKid2DigitalMan]

Ela:

It looks like you need an amplifier for that unit. The sensor alone probably has a very high output impedance which is probably causing the input end of your DAQ card to build up a charge, that is why you set it drifing to the rails over time.

You could try connecting the sensor to the DAQ in the differential mode of operation using a pair of bias resistors, refer to the manual of your DAQ to see how to do this.

-AK2DM

Message Edited by AnalogKid2DigitalMan on 02-05-2010 09:06 AM