4_MAE 334Woodward - lab3

4_MAE 334Woodward - lab3 - the Virtual Bench Data Logger...

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MAE 334 Lab 3 3. Next, turn on the Virtual Bench Digital Multi Meter and observe the voltage on channel 0 (with the experiment wiring in place). When the five-volt supply is turned on, the multi-meter should read about 2.5 volts (see Figure 3) depending on the lab temperature. 4. After the output voltage is established, click on the “Stop VI” button within the dialog window and then exit the dig-trigger.vi (leaving the voltage turned on) by pressing the X at the top right corner to close its window. You will also have to close the LabView Express window which then appears. Note: it is important to exit the digital trigger program with the established output voltage. This retains the 5 volts across the thermistor circuit but avoids cross talk with the Data Logger which may increase noise levels in the collected data. 5. Confirm that the multi-meter remains at about 2.5 volts and then close the Virtual Bench Digital Multi Meter. You may open it during your experiments as needed but do not use it during data logging. For most of your data recording you will use
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Unformatted text preview: the Virtual Bench Data Logger and record runs of two minutes in length. Suggested settings for the logger are shown in Figure 4 with timing and file settings as shown in Figures 5 and 6. During this experiment you will want to convert the voltage values that you record into temperature in degrees Celsius, the nominal calibration equation below may be used for our thermistor circuit: T (Celsius) = -17.58 V (volts) + 69.18 Using this equation with a typical starting voltage of 2.52 (Figure 3) gives a room temperature of about 25C. If you feel that your thermistor has drifted significantly from the nominal calibration, you may adjust the offset value (69.18) as you think appropriate. However, specific temperature values are not too important in this lab since most of the calculations are based on relative temperature variations, including (T - T lab ) and dT/dt. Figure 5. Timing Arrangements 4 of 9...
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