Download lab #8 thevenin`s theorem

ELEC195 LAB #8 2/6/03 J. F. Santacroce
1
NAME:____________________________
ELEC195 CIRCUIT THEORY II
PARTNERS:________________________
________________________
DATE:_____________________________
LAB #8 THEVENIN’S THEOREM
OBJECTIVE:
To calculate the load voltage and load current using Thevenin’s Theorem.
To verify your results by using Pspice simulation to verify the load voltage and load
current for the circuit.
EQUIPMENT:
HP-33120A Function Generator
HP-54600 Oscilloscope
HP-34401A Multimeter
1 - Analog Breadboard
1 - CDA 3 Decade Capacitor Box
1 - CDA 5 Decade Capacitor Box
1 – Resistor Decade Box
PARTS & SUPPLIES
1 – 100 , ¼ W Resistor
1 – 220 , ¼ W Resistor
1 – 330 , ¼ W Resistor
2 – 0.1 uF, Capacitors
1 – 0.047 uF, Capacitor
1 Sets Banana to Alligator Clip Leads
2 Sets BNC to Alligator Clip Leads
1 Set BNC to Alligator Clip Leads( Blue
Band).
DISCUSSION:
The series-parallel circuit shown in Figure #1 is to be analyzed using Thevenin’s
Theorem. During this experiment you will measure Thevenin’s equivalent circuit and
subsequently verify your results using Pspice.
Thevenin’s equivalent voltage directly measured as the open-circuit voltage with the load
capacitor, CL removed. Thevenin’s equivalent impedance will be calculated by first
measuring the following parameters; vOC (open-circuit voltage) and iSC (short-circuit
current) and then satisfying the equation given below:
ZTH = vOC / iSC
ELEC195 LAB #8 2/6/03 J. F. Santacroce
2
SCHEMATIC:
Figure #1
REQUIRED EQUATIONS:
ZTH = vOC / iSC
Z1 = R1 + jXC1
Z2 = R2 + jXC2
Z3 = R3
ZL = CL
PROCEDURE:
1. Construct the circuit shown in Figure #1. Set the HP-33120A Function Generator to a
5VRMS (sine wave) with the frequency at 16kHZ.
Measure the required circuit parameters, in polar form, as required in the following table.
e = _________________ (polar form)
iL = _________________ (polar form)
vL = _________________ (polar form)
VOC = _______________ (polar form)
iSC = _________________ (polar form)
2. Construct Thevenin’s Equivalent circuit using both the Decade Resistor Box and the
Decade Capacitor Box and measure:
vL = _________________ (polar form)
iL = _________________ (polar form)
ELEC195 LAB #8 2/6/03 J. F. Santacroce
3
3. Calculate the following circuit values:
XC1 = XC2 ______________(polar)
XC1 = XC2 _____________ (rectangular)
Z1 = ___________________(polar)
Z1 = ___________________(rectangular)
Z2 = ___________________(polar)
Z2 = ___________________(rectangular)
Z3 = ___________________(polar)
Z3 = ___________________(rectangular)
ZL = ___________________(polar)
ZL = ___________________(rectangular)
ZTH = __________________(polar)
ZTH = ___________________(rectangular)
eTH = __________________(polar)
*iN = ____________________(polar)
vL = ___________________(polar)
*Norton’s equivalent
iL = _____________________(polar)
PSPICE VERIFICATION:
The remainder of this experiment is to be performed using Pspice in conjunction with
Thevenin’s Theorem to verify the measured results.
1. Simulate the entire circuit of Figure #1 and solve for vL across CL. Please note that
Pspice needs a dc-path from every node to ground. Therefore, place a 100 Meg- resistor
across the output to ground as part of your simulation set-up. Measure vL by placing
VPRINT1 at the node above CL.
Set the following parameters;
VSIN:
DC=0
AC=5V
VOFF=0
VAMPL=5V
FREQ=16.0KHZ
TD=0
ANALYSIS SETUP:
ACSWEEP;
TOTAL PTS 1
STARTFREQ 16KHZ
END FREQ 16KHZ
VPRINT1:
DC=0
AC=?
MAG=ok
PHASE=ok
IMAG=ok
REAL=ok
TRANSIENT SETUP:
PRINT STEP 5us
FINAL TIME 200us
ELEC195 LAB #8 2/6/03 J. F. Santacroce
4
2. Using the techniques of Part 1, find Thevenin’s equivalent voltage. This is the opencircuit voltage and don’t forget the 100Meg- resistor to ground.
3. Find Thevenin’s equivalent impedance using the relationship:
ZTH = vOC / iSC.
Therefore, find iSC by using Pspice and placing a short-circuit across the output. This is
accomplished by using IPRINT as the short!
4. Build up Thevenin’s circuit by using the real part of ZTH as RTH and the imaginary part
as XTH , the reactance of CTH. Calculate the capacitor value from this reactance! Put the
0.047uF capacitor back as the load and simulate the output voltage.
5. Compare the simulated results with the measured results.