connecting the NI 9944 to Pasco load cell

[MEMEsomday]

I would like to connect teh PASCO PS-2200 Load Cell to the NI 9944. I have performed soldering so that such a connection is possible. Can someone tell me what the EX+ and IN+ are for?  which one is for the positive signal and the negative signal?

[RavensFan]

Ex+ means the positive side of excitation.  In+ means the positive side of the input reading.

Where did you see these designations, on the NI module or the load cell?

Generally load cells are a full bridge arrangement which means at least 4 wires:  two for excitation, two for sensing.  But you said you have an NI-9944 which is for reading quarter bridge strain gages.

Are you sure you are using the right DAQ device for your load cell?

[MEMEsomday]

On page 3 of this Pasco PS 2200 manual ftp://ftp.pasco.com/Support/Documents/English/PS/PS-2200/012-10638A.pdf  you can see the pinouts. Currently I have connected pin 1 of the Pasco load cell to EX + of the NI 9944 and pin 3 of the load cell to IN+ of the NI 9944 following what I understand from the instructions in this link http://digital.ni.com/public.nsf/allkb/F47EFDB8B1992282862572AD007CE9C3  . I then used a jumper wire to connect IN+ to QTR of the NI 9944 by making a sort of hook with one end of the jumper wire so that it can hook to the wire connecting IN+ to pin 3 of the load cell. The Shield pin of the NI 9944 is not connected to anything. Is this setup correct? Pins 2 and 4 of the load cell are connected to a power supply. Maybe I do not have a clear understanding of the terminology used in the instructions.

The DAQ used is the NI cDAQ-9172 and the module is the NI 9237. I believe these devices are all compatible with each other. On page one of the NI 9944 user guide http://www.ni.com/pdf/manuals/374437a.pdf  it says that a plastic tie strap and some screws are required. What purpose do they serve? Is it really necessary? The goal is to make a quarter bridge. We believe that the signal sensed by the load cell is resistance and so the NI 9237 would make a Wheatstone bridge and the NI 9944 would complete it. Supposedly the readings would be in volts. The signal received by LabVIEW is just a straight line at 0.05 V whether mass is applied or removed from the cell.

Thanks for your help.

[RavensFan]

That link looks like it is a full bridge load cell.  +4.2V would be equivalent to Ex+.  Gnd is probably Ex-, but generally no corner of a full bridge is going to be tied to ground.  + Strain gage output and - strain gage output would go to In+ and In- on a DAQ card.

However, you have a quarter bridge DAQ device with the NI-9944.  That will not work with a full bridge load cell.  You should just be using the NI-9237.

You should probably contact your local NI sales rep and run through this with them to verify you have the correct hardware for what you are trying to do.