Bias Circuit

PA.3 Plotting Measured Samples
• Open PlotSamples.vi. Prepare the Diagram for displaying the samples. For
high resolution (discussed later), set the high limit and low limit as shown in
the example to 1 V and 0 V, respectively. The number of samples can be 10
to 100 and is not critical at this point. We only want to gain some experience
with graphs and display the point scatter expected under the conditions set up
here. The number of samples is 40 in the example.
• Go to the Front Panel to run the VI with the voltage sent out similar to that
shown in the example, 0.1 V. This must be lower than the high limit setting
for the DAQ input, which is 1 V. At this voltage level, there will certainly be
some data scatter. Click on the Y-axis numbers, go to Formatting..., and set
the Digits of Precision to 3.
• Now run the VI repeatedly. Note that even though there is data scatter, the
average value is relatively constant (in the Received Volts Indicator). Note
also that the X-axis is in msec. The total time in the graph is 40 times 1 ms
(including 0) and AI Acquire Waveform.vi is set for 1000 samples/sec.
• To set (or verify) the same sample rate as in the example, open the Front
Panel of AI Acquire Waveform.vi. Type in the number 1000 for the sample
rate and default the value. To default, Right Click on the indicator and go to
Data Operations>>Make Current Value Default. Save the VI and close.
• Re-run the VI with Send Volts = 0.015. Subtract the difference between the
measured value of 0.1 V and 0.14 V sent out. Compare the difference with the
resolution expected, as obtained from Table PA.2. Note that the high limit is
1V and the mode is Unipolar.
TABLE PA.2
Range Resolution
Unipolar 0 to +10V 2.44 mV