Posted 07 May 2010 - 08:47 AM
Posted 07 May 2010 - 11:06 AM
Posted 07 May 2010 - 11:22 AM
The circuit is to be made up of a potential meter so that the resistance can be varies via the GUI and the current and voltage is to be read back by the Labjack U12. Please advice if this setup is possible for this experiment. And if possible is there'a a potential meter that can be recommend.
LabVIEW GUI: It is easy to make your own, but you might start with the example "simple eanalogin loop with chart.vi":
If you want to use a ready-to-run program, I would use LJlogger, LJsimplelog, or LJstream, rather than LJscope. LJscope would be when you want to maximize speed and act like an oscilloscope.
Excitation: You need an excitation voltage to put across your pot. I suggest just using +5V, although you could use an AO channel.
Current Measurement: Typically you measure current by measuring the voltage across a current shunt, which is just a know resistance. That is what a DMM does. In this case, you can just use the DMM beforehand to measure the total resistance across the pot, then by measuring your excitation voltage during the experiment you can calculate current through the pot.
Voltage Measurement: Measure the excitation voltage and pot output voltage using analog input channels. Keep your pot resistance lower to minimize errors due to the analog input bias currents on the U12 (our newer U3/U6/UE9 would virtually eliminate this issue). I suggest 1k at most, although you could certainly do down to 100 ohms if using +5V as your excitation.
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