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SCXI-1120 module

I am working a project where we want to measure temperature and pressure with LabVIEW. The pressure transducers put out a 4-20mA signal. My customer already has the following equipment. SCXI 1001 chassis, (2) 1120 modules, a 1320 terminal block and a 1328 terminal block. I am fairly new to the hardware side of this but it appears to me that I can use the 1328 with an 1120 module for the temps and the 1320 with the other 1120 module for the transducers with the 4-20mA signal. Are my assumptions correct? Also is the SCXI-1001 chassis powered by battery?
Thanks for any help.
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Message 1 of 6
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Your assumptions are right on the money. With this hardware selection the 1328 is better for the temperature measurements and the 1320 would be better used for the pressure transducer measurements. Both of these terminal blocks are compatable with the 1120 modules.

The SCXI-1001 chassis actually uses AC power. You can get a sine wave DC-to-AC power inverter to power your AC chassis with a DC power supply if you wish.
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Thanks for your response. Now for choosing a DAQ board, I've got it narrowed down between the NI PCI 6011E and the 6033E, but I think since I will have 8 thermocouples and 3 pressure transducers, that rules out the 6011E. Also, what is the difference between single ended and differential? Which should I use?
Thanks again for your response.
Dave
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Any DAQ card you choose will (as a rule) only use 1 input channel (channel 0) for data transfer between the SCXI chassis and the DAQ card. All of the data is multiplexed through channel 0 of the onboard DAQ card. So, you only NEED 1 analog input channel on your DAQ card. The 6011E is not the best choice for SCXI since you can not use the inherent (pseudo) SSH capability. In addition, the SCXI bus is band limited to a maximum aggregate sampling rate of 333 ksamples per second. So, the DAQ board would be limited to the 333 ks limit with SCXI. My personal favorite is the PCI (or PXI) 6052E board. It is rated at 333 ksamples per second at 16-bit accuracy - it is a superb match with the SCXI line.

As for the question about single-ended or differential
, well.., that is an entire DAQ lesson in itself. Simply put ... Single-ended means you connect the positive inputs to the designated channel and all of the ground are tied together. Differential means you attach the positive and ground inputs from each sensor to individual channels (see the appropriate users manual). Differential gives superior signal-to-noise ratio and commom mode noise rejection - at the expense of twice the channel count. The "gross rule-of-thumb" is: If your signal source is grounded (by means of a three-prong plug - say a stand-alone Vischay Amplifier) and the signal is greater than 1 V, and, the input wire is shielded and properly grounded, and, the wire length is less than 10 feet -- you can use single-ended: Otherwise, use differential.
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Thanks for your informative response.
I was looking at the specs for the 1328 terminal block and was unable to find how many thermocouples could be wired to it. I now have 15 thermocouples, does that mean I need (2) 1328 terminal blocks and (2) 1120 modules?
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Correct. Each 1120 has 8 isolated inputs. You will need two 1120s and two 1328s.
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