Using pressure transducers and load cells on SCXI 1303 card

[deedoo]

Hello all:

I am currently using a PXI 1052 with an SCXI 1303 card and two SCXI 1314 cards on it.  I have a test where I am measuring several channels of displacement measuring potentiometers, several quarter bridge strain gauges, a pressure transducer, and two load cells. 

My problem is the following.  I am trying to run the load cells and pressure transducers through the 1303 card.  I have the pressure transducer on a separate 10 volt power supply, the load cells on a separate 10 volt power supply, all displacement sensors on their own 10 volt power supply and the strain gauges are excited by the 1314 card.  The pressure transducer is an Omega brand with 4 wires and output excitation of 0-100 MV.  The load cells are full bridge configuration with 120 ohm resistors.  My first question is this: is it proper to run the pressure transducers and load cells on the 1303 card?  Would it be better to somehow wire them through the strain gauge card (1314)?

The reason I ask is that when I use the VI I have setup the pressure transducer has the following problems.  As soon as I strat the VI it begins jumping between -30 to +30 mv readings on the VI.  When I put a volt meter at the terminals it is steady at around 3 mv.  Thus, this leads me to believe there could possibly be a problem with the VI?  The load cells also are tend to jump quite a bit within the VI at low readings.  If I begin to run pressure through the transducer it starts to equalize within the VI and reading are close to what I would expect.  All displacment sensors and strain gauges are stable.

I tried a separate VI where I only viewd two channels at a time that I could choose what they would be.  If I monitor the pressure transducer and load cell in this VI both are very stable.  The pressure transducer initial offset reading of 3mv displays in this VI as it does on the volt meter.  I am wondering is there something wring within the VI or is there something wrong with wiring these pressure transducers and load cells into the 1303?  Any help would be greatly appreciated.

[aeastet]

The 1303 is a thermocouple terminal block. It is not a module. If you take the terminal block off of the module you will be able to see what module you are using. The 1314 is a strain gage terminal block. Again here you would have to remove the terminal block to see what module you are actually using.

Given that the 1303 is a thermocouple terminal block I would say that it is not appropriate to use this for strain based sensors such as the loadcell or pressure sensor. NI has an isolated AI module for the SCXI that would be perfect for this application as long as you purchase the correct terminal block to go with it. You can not interchange terminal blocks just because the fit and expect them to work. Read the owner manual for the actual module that you own and it will tell you what terminal block to use.

I hope this helps

[deedoo]

aeastet:

The terminal block is the 1303 and the module is SCXI 1102.  Sorry for the confusion with the wording.  I think the problem may have had something to do with the VI in which I was running it.  When I made a new VI the sensor read without any problems. 

I have always used the pressure transducer with the 1303 card and never had problems.  I usually run it off a separate power supply, otherwise there is a reasonable amount of background noise.   I will look into the module you described and see if it may be more approrpiate for my intended application.  Thanks for the input.