I am trying to configure a linear motion potentiometer on the SCXI-1100 with a 1300 terminal block. My first problem is that my voltage readings are all screwed up. When I just try to measure the voltage by putting the positive lead on CH0+ and the negative lead on CH0-, interesting things happen. When my voltage source is off, it gives a reading of 10V. When it is on but turned down all the way, it is unstable with peaks but no troughs. When it is turned up just a little bit (not nearly 10V). It jumps to 10V. To connect my potentiometer, I run the voltage across the whole thing and then put the middle wire into the positive channel input and put the negative channel input common with the negative voltage source. When I don't touch it, the signal is pretty steady close to zero. When I move the shaft a tiny bit, it jumps up to 10V and stays there the rest of the way in. This happens reguardless of whether my voltage source is set to 10V. I tested my voltage source with a multimeter and it is working correctly. I believe I have all the wiring right, but there may be something that I have missed (I am very new at this). If anyone can help, I would appreciate it as I have been working on this for a very long time with no success. -Andy
Hello, It's me again. I was a doofus and was working on channel 8 on accident. However, I don't know if what I have now is right. I get readings with my voltage and with the potentiometer, but on the test panel they show up like a sine wave rather than a steady line. The result is a very noisy signal. I am not sure about the jumpers and if I have to change any of those. Right now I believe they are on the factory settings. Is this normal, or do I need to fix something. The reading straight from my power source is also wavy. -Andy
Please keep in mind that the test panel tends to autoscale and zoom in to your measurement. This can make a straight line look like a sine wave (or a noisy signal) because it is zoomed in so far. What is the average reading MAX is showing? If you turn autoscaling off and change the graph limits to +/- 10V, how does the measurement look? If it still looks noisy, how much noise are you reading? 1mV, 10mV, 1V?
The SCXI-1100 includes both 4Hz and 10kHz filters. Once you determine the frequency of the noise you are receiving you may want to consider using one of these built-in filters. The 4Hz filter is excellent for removing common 60Hz noise.
Also, check out the following Application Note on wiring and noise. It is a great referen ce.
Field Wiring and Noise Considerations for Analog Signals http://zone.ni.com/devzone/conceptd.nsf/2d17d611efb58b22862567a9006ffe76/01f147e156a1be15862568650057df15?OpenDocument
As for jumper settings and other related questions, the SCXI-1100 User Manual is the best resource. You can find all manuals online at http://www.ni.com/manuals