ELEC 242 Lab

Experiment 8.2

Dynamic Performance

Part 1: Step Response



Step 1:

 Remove any weights from the hook.

Step 2:

 Replace $R_F$ with a 220k ohm resistor.

Step 3:

 Load the "Step Response" Labview program. Set the Duration to 2.0 sec and the Amplitude to 3.5 V.

Step 4:

 Run the program and print the response.

Step 5:

 Repeat the measurement for each of the values of $R_F$ used previously. Sketch each response and make a printout for $R_F$ = 4.7M.

Because of the increasing overshoot as the gain is increased, it will be necessary to reduce the amplitude as $R_F$ is increased. Here are some suggested values:

$R_F$ Amplitude
220k 3.5
470k 3
1M 3
2.2M 2
4.7M 1

Part 2: Frequency Response



Step 1:

 Connect A/D input 4 (pin 46 on the interface board socket strip) to $v_{des}$ .

Step 2:

 Load the "Frequency Response" Labview program. Set the parameters as follows:
  • Flo=0.5 Hz
  • Fhi=5.0 Hz
  • Nsteps=20
  • Amplitude=2 V
  • Magnitude Scale: dB
  • Frequency Scale: Log

Run the program for each of the values of $R_F$ used in previous measurements. As in the case of the step response, it will be necessary to reduce the amplitude as $R_F$ is increased. Here are suggested values.

$R_F$ Amplitude
220k 2.0
470k 1.0
1M 0.5
2.2M 0.2
4.7M 0.1


Step 3:

 For the underdamped cases, estimate $\omega_d$ and $Q$ from the frequency response.

Question 3:

 Based on the analysis in the Background section (and performed in class) summarize the expected behavior of the system dyanmics as a function of summing amplifier gain $A$ . Is this behavior reflected in your observations?