Trouble reading Omega pressure tranducer with SCB-68

[dbeerer]

Hi,

I am having some difficulty setting up a pressure transducer read with my NI hardware.  I have an Omega PX-205 pressure transducer : http://www.omega.com/manuals/manualpdf/M2165.pdf  that I am trying to hook up to my SCB-68 box, and I am using Labview 7.1 with NI-DAQmx to read the signal and I have a PCI-6023E card in my computer.

My box reads all my other eqiupment fine, but I just aquired the pressure transducer and so far its not working out.  I've wired the trasducer to the scb box and power supply as shown in the pdf and I'm seeing the following results:

When I turn on the power supply, my voltage read out goes immediatly to +10 volts, which is the "MAX Input Range" value in my MAX window.  I tried increase the Max Input range, but anything up +10 volts gives me a "Error -200077 occurred at DAQ Assistant"
message which I am not sure how to fix.  I have also tried to read a current from the box and it gives me a similar problem, resulting in  + 40 mA signal which again is the Max Input range.  After I unplug the power supply, the signal drops back down to zero. My power supply supplies 16 volts DC. 

So I'm not sure if my wiring is not correct, or if its my transducer, or the way I am trying to read the signal in MAX/Labview.  I've been looking for some hints on some of the other posts like: http://forums.ni.com/ni/board/message?board.id=250&message.id=20643,  but I haven't been successful yet.

Any advice on what to try next would be very helpful,

Thanks,

-David

[tnek]

Hi David,

After taking a quick look at the transducer you mentioned, it looks like it outputs current. In order to measure current, you will need to provide an external resistor to you DAQ card and measure the voltage drop across the known resistance. The SCB-68 connector block user manual provides good information on how to accomplish this on page 5-16. When creating a task in DAQmx to measure current, there is a field which asks for the location and resistance of this shunt resistor. The calculation will be made in the task based on the information entered and the voltages acquired and you should be able to monitor the current output from your transducer. There is more information on how to make current measurements in this article. I hope this helps.

Regards,
Kent
Applications Engineer


Message Edited by tnek on 04-18-2008 02:56 PM

[dbeerer]

Bingo!  The resistor did the job.  Thanks a lot!

Dave