SCXI-1127 problems

[Leonard Mills]

We are using a SCXI-1127 module, a NI-1331 terminal block, and a NI-1000 chassis. I set up the chassis and module correctly and wired up for 4 wire resistance measurements. I Connected the signal to channel 0A and 0B for 4 wire measurements. When i go to test, i can't get any measurements. Under the properties for the 1127 we have it set up for 4 wire mode on channels 0-15. We tried to make a virtual channel then run the tests on that channel and can't get any resistance measurements. Any ideas what could be going on here?

[Claudia]

Hello Leonard,

First of all I would like to make sure you are connecting your signals correctly.

In the NI Switches Help (April 2003), go to the chapter "NI Switches Help >> Device Overview >> NI SCXI-1127/1128 >> 4-Wire 16x1 Multiplexer Topology". It shows there how to connect your signals and it says "In 4-wire mode, connect your excitation or source leads to xA+ and xA- and your measurement or sensing leads to xB+ and xB-".

Question 1: Are you connecting the excitation signal to 0A+ and 0A-, and the resistance legs to 0B+ and0B-?

Question 2: Use the example program "niSwitch Making Connections on a Switch.vi" in LabVIEW that s
hips with the NI-SWITCH 2.0 (or later) driver to choose the appropriate topology and to connect CH0 to COM0. If you measure in your terminal block the pins that correspond to OUT0 and OUT2, can you see the appropriate signals?

Question 3: What device are you using to measure signals from the switch? The NI 4070 DMM? Another NI DMM? If so, connect AB0 to OUTo and AB2 to OUT2 and try to get the readings in the DMM from the backplane of the chassis (see Switches Help for more information).

Question 4: How are you creating a Virtual Channel?

Talk to you later,

Claudia Lorente
Applications Engineer
National Instruments
http://www.ni.com/ask