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Step 1: |
Get an
inductor
from the cart.
With the DMM, measure its resistance.
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Step 2: |
Wire the following circuit
(this is just the previous circuit with the resistor replaced by
an inductor).
Because of the output resistance of the function generator ( ) and the internal resistance of the inductor ( ) the circuit actually looks like this: |
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Step 3: |
Set the function generator to produce a 50 Hz,
2 V p-p square wave.
Sketch the output waveform,
.
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Step 4: |
We can eliminate the tedium of sketching waveforms by
using Labview to capture and print them.
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Step 5: |
Disconnect the function generator from the circuit.
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Step 6: |
Reconnect the DAQ card inputs and outputs as
follows:
connect D/A output 1 and A/D input 4 (pins 11 and 5 on the interface board socket strip) to
and
connect A/D input 5 (pin 6) to
.
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Step 7: |
Load the "Step Response" program from the
Start menu by following the path Programs -> Labview -> 242 -> Step Response.
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Step 8: |
Set the
Duration
to 0.02 sec and the
Amplitude
to 0.5 V.
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Step 9: |
Run the program by pressing the Run button or CTRL-R.
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Step 10: |
Print a copy of the step response and put it in your lab notebook.
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Step 11: |
Estimate the damped natural frequency (
):
Count out several cycles of the oscillation (say 10).
Measure the length of time taken by this interval.
Divide the number of cycles by the total time to get the frequency in Hz.
Multiply by
to get
in radians/sec.
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Step 12: |
Estimate the damping coefficient (
) by finding the
time constant of the envelope formed by successive positive
peaks of the oscillations.
| |
Question 3: |
Using the values of R, L, and C for your circuit, find the coefficients of the characteristic equation. From these determine the expected values of and . How do these compare with the values you measured? |
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Step 1: |
Reload the
"Frequency Response" Labview program.
Set
Flo
to 200 Hz,
Fhi
to 2000 Hz,
and
Amplitude
to 0.1 V.
| |
Step 2: |
Run the program and print a copy of the output for
your lab notebook.
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Step 3: |
Because the peak in the frequency response is so narrow,
the small number of frequency samples taken in the previous
measurement do not accurately measure its height.
Estimate the frequency of the peak from the
previous plot.
Set
Flo
to be 100 Hz less and
Fhi
to be 100 Hz more than your estimated frequency.
Run the frequency response program again.
If the peak isn't centered in the display
(or if you missed it entirely), choose new frequency limits and try again.
When you get a good plot, print a copy for your notebook.
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Step 4: |
From this plot, measure the maximum value of the gain and the frequency at which it occurs. Also measure the 3 dB bandwidth, the difference in frequency between the two points on the curve where the gain is 3 dB below its peak value. |