11-21-2013 10:29 AM
Hello everyone,
I have two issues with our Keithley 2400, which we control through Labview, and I would be very grateful for some help/advice. The issues are listed below:
1) We use the 2400 for 4-point probe measurements, so we plot graphs of current vs voltage to get the resistance from the slope of the curve. However, when we look up the data generated during a measurement, the voltage sweep values that we program often, but not always, do not match the measured voltage values. For example, what was meant to be 1 V, might actually end up being 1.2 V or maybe 0.8 V, this can be both positive and negative with respect to the programmed values and is not constant. This also leads to the fact that our curves, although straight (so Ohmic conductor), do not go through the (0, 0) point on the graph.
2) Second problem is that we would like to determine what is the time between successive measurements in a voltage sweep. We have tried some example vi files that by default come with the Labview, e.g. Keithley 24XX Read Multiple - SW Trigger or Keithley 24XX Read Multiple. If someone knew how to find the time separation, then we would be grateful. We only have control over the number of invididual readings taken and the timeout, which we guess is the maximum time allowed for the measurement.
Many thanks!
11-26-2013 07:01 AM
Good Afternoon PiotrW,
1. Could you please provide the code you are using to program the voltage sweeps?
2. You could use the timestamp output of the Keithley 24XX.lvlib:Read (Multiple Points).vi to allow you to find the time difference between successive samples. It should be a simple case of subtracting succesive measurements from each other to find the time difference between data points.
Regards,
Al