Laboratory Exercise - Motors, Time Constants and Starry Nights

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        In this lab you need to measure the time constant of a motor.  Here are the salient issues.

• The motor is a DC motor.
• Set up the supply and motor so that you can apply 5v to the motor.
• Be sure that there is only one disk on the motor.
• The motor has an AC tachometer which measures rotational rate.
• Connect the AC tachometer to the oscilloscope.
• Apply the DC voltage to the motor.
• Show your circuit in your report.  Show all of the connections above.  (Those connections are the power connections to the motor and the signal connections from the AC tachometer to the oscilloscope.)32
• Record the AC tachometer signal on the oscilloscope and capture the data using IntuiLink.
• Click here to get instructions for running IntuiLink and saving your data in a data file you can bring up in Excel
• Re-do turning the DC voltage off, and letting the system come to rest.
• Determine the time constant of the system.
• Re-do adding the second disk.

For your report answer the following questions which define what is on the summary sheet.

1. What is the "Up" time constant?
2. What is the "Down" time constant?
3. Are the two time constants (Up and Down) the same (within experimental accuracy)?
4. What effect does adding the second disk have?  Can you explain your result?