How connect NI USB 6008 to BNC out on Transonic T110 w/t ground loop noise?

[Kark]

How can I connect the NI USB 6008 data acquisition device to the BNC connector (pulsatile flow out) on Transonic T110 flow meter without experiencing ground loop noise? I have tried cutting off one end of a BNC cable, trimming to reveal the core wire, and connecting the core wire to one of the analogue inputs on the NI USB 6008. I get a signal but it does not correspond to the readings on the flow meter.

[Sarah_Coleman_NIUK]

Hi,
 
To get rid of ground loops you should connect the device to the USB-6008 in a differential configuration. You can connect the positive input to AI0 and the negative or ground input to AI4 (AI0 and AI4 are a differential pair on the 6008).

For more information on signal connections in DAQ have a look at the following tutorial:
Field Wiring and Noise Considerations for Analog Signals

[Kark]

Hi Sarah The BNC cable consists of 4 concentric layers – from inner to outer: core wire, insulation, braided tubular wire, and outer insulation. If I connect the core wire to A10, how do I connect the braided tubular wire to A14 – is there an adapter that converts BNC cable to two terminals?

[Sarah_Coleman_NIUK]

Hi,

You can strip back the braided wire then twist it so it will fit in the connector. You could put some solder along it to tidy it up a bit.

[AnalogKid2DigitalMan]

Here's some off-the-shelf solutions

http://www.alliedelec.com/catalog/pf.asp?FN=53.pdf

[Kark]

Sarah / Analogue Kid Problem solved. I have tested it using the make do cable and the values correspond. I have ordered a BNC cable adapter locally from www.radionics.ie that, when the NI screw fitting is removed, plugs directly into the NI USB 6008. See link for cable: http://www.radionics.ie/cgi-bin/bv/rswww/searchBrowseAction.do?D=bnc&Ntt=bnc&Nr=avl%3aie&Ntk=I18NAll&N=0&Nty=1&name=SiteStandard&forwardingPage=line&R=2967747&callingPage=/jsp/search/search.jsp&BV_SessionID=@@@@0098981695.1157726108@@@@&BV_EngineID=cccfaddikilddmhcefeceefdffhdgmo.0&cacheID=ieie Thanks a mil Kark