AC Isolation of USB-9233

[jmaung]

Hi,

I have a USB-9233 acquisition unit. The unit acquisition channels have IEPE/ICP current.

I would like to connect an AC signal from a sound level meter which doesn’t require the IEPE/ICP current.

The voltage across the input terminals is around 20 volts and I cannot directly connect the output of the meter to the acquisition channels without damaging the meter.

Currently I have 1 mfd capacitor in series with each of the acquisition channels to isolate the IEPE/ICP current. The problem with this is that there is cross talk in the signals.

If I short input channel 1, 2 and 3 with a signal input in channel 0, then there is no cross talk.

I have tried looking in the support documents but there is nothing there about being able to turn of the IEPE/ICP current for the USB-9233 unit.

Are there other solutions/products that will isolate the IEPE/ICP current of the USB-9233 so that I can connect the AC signal from the meter? Does the USB-9233 need to output the IEPE/ICP current so that there is no cross talk?

.

[kalyanramuv]

Hello,

This discussion forum link addresses this issue.

http://forums.ni.com/ni/board/message?board.id=250&message.id=17459

Basically, you would need voltage follower circuit . source follower amplifier will remove the IEPE from your signal if you are worried about the 2mA of current that your device would see if connected directly to the cRIO 9233. PCB has a handful of different types of in-line source followers.
To be more specific, we have tested PCB's ICP source follower amplifier model# 401A04. Contact PCB for more details since it is not listed on their website.
Please let me know if this helps.

Kalyan