Name: Due date: Grade:

ECE 2006 LABORATORY 7

RC AND RL TRANSIENT RESPONSE

Objectives

The learning objectives for this laboratory are to give the student the ability to:

  • use the function generator to generate a step input with an appropriate repetition rate.
  • use the oscilloscope to measure the time constant, the initial value, and the final value of an exponential response.
  • use the function generator to generate a pulse input with an appropriate repetition rate.
  • use the PSPICE transient response tool.

References

D. E. Johnson, J. R. Johnson, J. L. Hilburn, and P. D. Scott, Electrical Circuit Analysis. 3rd Edition, Prentice-Hall, 1997.

Background

See above reference, Chapter 6, pp. 244-255, for PSPICE analysis of RC and RL transient response.

Equipment

Oscilloscope,

Function generator,

Digital multimeter,

Resistor, 680 .

Capacitor, 1.0,F.

Procedure

1.RC circuit capacitor voltage transient response to a unit step input.

1.1For the circuit in Figure 1 and a unit step generated in the function generator, calculate the initial value, v(t=0+), final value, V(t=), and time constant, Tc, and record in Table 1. Using these values, write the transient time response equation for the capacitor voltage, V(t), and record in Table 1. Assume the function generator internal resistance is 50 .

1.2With the RC circuit disconnected, adjust the function generator to produce a repetitive pulse that is 0 volts for about 10 time constants, then +1 volts for about 10 time constants.

1.3Connect the circuit in Figure 1. Measure the initial value, v(t=0+), final value, v(t=), and the time constant, Tc, from the oscilloscope and record in Table 2. Using these values, write the transient time response equation for the capacitor voltage, v(t), and record in Table 2.

2.RC circuit resistor voltage transient response to a unit step input.

2.1For the circuit in Figure 2 and a unit step generated in the function generator, calculate the initial value, v(t=0+), final value, v(t=), and time constant, Tc, and record in Table 1. Using these values, write the transient time response equation for the resistor voltage, v(t), and record in Table 1. Assume the function generator internal resistance is 50 .

2.2With the RC circuit disconnected, adjust the function generator to produce a repetitive pulse that is 0 volts for about 10 time constants, then +1 volts for about 10 time constants.

2.3Connect the circuit in Figure 2. Measure the initial value, v(t=0+), final value, v(t=), and the time constant, Tc, from the oscilloscope and record in Table 2. Using these values, write the transient time response equation for the resistor voltage, v(t), and record in Table 2.

3.RL circuit inductor voltage transient response to a unit step input.

3.1For the circuit in Figure 3 and a unit step generated in the function generator, calculate the initial value, v(t=0+), final value, v(t=), and time constant, Tc, and record in Table 1. Using these values, write the transient time response equation for the inductor voltage, v(t), and record in Table 1. Assume the function generator internal resistance is 50 Ω.

3.2With the RL circuit disconnected, adjust the function generator to produce a repetitive pulse that is 0 volts for about 10 time constants, then +1 volts for about 10 time constants.

3.3Connect the circuit in Figure 3. Measure the initial value, v(t=0+), final value, v(t=), and the time constant, Tc, from the oscilloscope and record in Table 2. Using these values, write the transient time response equation for the inductor voltage, v(t), and record in Table 2.

4.RL circuit resistor voltage transient response to a unit step input.

4.1For the circuit in Figure 4 and a unit step generated in the function generator, calculate the initial value, v(t=0+), final value, v(t=), and time constant, T c, and record in Table 1. Using these values, write the transient time response equation for the resistor voltage, v(t), and record in Table 1. Assume the function generator internal resistance is 50 .

4.2With the RL circuit disconnected, adjust the function generator to produce a repetitive pulse that is 0.0 volts for about 10 time constants, then +1 volts for about 10 time constants.

4.1Connect the circuit in Figure 4. Measure the initial value, v(t=0+), final value, v(t=), and the time constant, Tc, from the oscilloscope and record in Table 2. Using these values, write the transient time response equation for the resistor voltage, v(t), and record in Table 2.

5.RC circuit capacitor transient response to a pulse input.

5.1For the circuit in Figure 1 and a unit pulse generated in the function generator from t=0 to t=1 msec, write the transient time response equations for the capacitor voltage, v(t), and record in Table 3. Assume the function generator internal resistance is 50 .

5.2With the RC circuit disconnected, adjust the function generator to produce a repetitive pulse that is 0 volts for about 10 time constants, then +1 volts for about 10 time constants.

5.3Connect the circuit in Figure 1.

5.4Sketch the response from the oscilloscope onto Figure 5 from t= 1.0 msec to t= +4.0 msec; use the beginning of the pulse as t=0.

5.5Write and run a PSPICE program for this circuit. Set the voltage pulse to 1 volts from t=1 to t=2 msec, zero elsewhere. Have the output plot in 0.1 msec increments from 0 to 5 msec.

6.RC circuit resistor transient response to a pulse input.

6.1For the circuit in Figure 2 and a unit pulse generated in the function generator from t=0 to t=1 msec, write the transient time response equations for the resistor voltage, v(t), and record in Table 3. Assume the function generator internal resistance is 50 .

6.2With the RC circuit disconnected, adjust the function generator to produce a repetitive pulse that is +1 volts for 1.0 msec, then 0.0 volts for about 10 time constants.

6.3Connect the circuit in Figure 2.

6.4Sketch the response from the oscilloscope onto Figure 6 from t= 1.0 msec to t= +4.0 msec; use the beginning to the pulse as t=0.

6.5Write and run a PSPICE program for this circuit. Set the voltage pulse to +1 volts from t=1 to t=2 msec, zero elsewhere. Have the output plot in 0.1 msec increments from 0 to 5 msec.

Conclusions

Normal conclusions based on experience gained.

Sample Calculations

Calculate Tc for RC and RL transient response circuit. Show derivation of v(t) for all four figures (calculated valuesTable 1).

Calculate Tc of all four figures (measured valuesTable 2).

Figure 1. RC circuit capacitor voltage measurement

Figure 2. RC circuit resistor voltage measurement

Figure 3. RL circuit inductor voltage measurement.

Figure 4. RL circuit resistor voltage measurement.

TABLE 1

CALCULATED TRANSIENT RESPONSE VALUES TO A UNIT STEP

Figure number / v(t=0+)
volts / v(t=)
volts / Tc
msec / v(t) – volts 0<t
t - msec
1
2
3
4

TABLE 2

MEASURED TRANSIENT RESPONSE VLAUES TO A STEP

Figure number / v(t=0+)
volts / v(t=)
volts / Tc
msec / v(t) – volts 0<t
t - msec
1
2
3
4

TABLE 3

CALCULATED TRANSIENT RESPONSE VALUES TO A PULSE

Figure number / v(t) – volts 0<t<1.0 msec
t - msec / v(t) – volts 1.0 msec<t
t - msec
1
2

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