ECE 206
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Lab 5: Basic Electrical Measurements
Laboratory Goals
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Familiarize students with the digital multimeter and the power supply
Calculate voltage and current values for two circuits
Construct resistive series and series-parallel circuits
Measure the resistance, current, and voltage of resistive circuits
Record results in the laboratory notebook
Pre-lab / lab reading
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Course Textbook
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Agilent 34401A 6 ½ Digit Multimeter User Manual:
http://www.home.agilent.com/en/pd-1000001295%3Aepsg%3Apro-pn34401A/digital-multimeter-6-digit?cc=US&lc=eng
Agilent E3631A, Triple Output Power Supply
http://cp.literature.agilent.com/litweb/pdf/E3631-90002.pdf
Basic resistive networks, ECE 203 textbook
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Equipment needed
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Lab notebook, pen
Agilent E3631A Triple DC Power Supply
Agilent 34401A Digital Multimeter
2 test leads, red, with banana/EZ Hook ends (located in your assigned equipment
cabinet)
2 test leads, black, with banana/EZ Hook ends (located in your assigned
equipment cabinet)
Parts needed
 Circuit breadboard
 Lab parts kit
 Resistor, 470 Ohms, ¼ W
 Resistor, 560 Ohms, ¼ W
 Resistor, 1.5k Ohms, ¼ W
 Resistor, 2.2k Ohms, ¼ W
 3 Capacitors, 1μF, 50V
 Resistor, 1 MΩ , ¼ W
 Brown jumper wires, 3 (U-shaped wires, found in the parts kit)
Lab safety concerns
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Do not make voltage measurements while the multimeter is set for current
measurements-you will blow the current limiting fuse!
Do not turn on the power supply until you have rechecked your circuit for correct
wiring
Do not allow the test leads connected to the power supply to touch each other
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Lab 5: Basic Electrical Measurements
1. Pre-Lab Design Calculations
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Measure R1, R2, & 10V then calculate IR1, IR2, VR1, and VR2 for Circuit 1:
Figure 1: Circuit 1
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Next, Measure R1, R2, R3, R4, & 10V then calculate IR1, IR2, IR3/IR4, VR1,
VR2, VR3, and VR4 for Circuit 2:
Figure 2: Circuit 2
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Create two tables in your lab notebook, with the headings shown below. (Be sure
to make five columns: Characteristic(voltage-V1 or current I2), Expected Value,
Measured Value, Error, %Error, Comment (error large because) and a row for
each of the values listed below:
Circuit #1
Vin
R1 R2 IR1 IR2 VR1 VR2
Circuit #2
Vin
R1 R2 R3 R4 IR1 IR2 IR3 IR4 VR1 VR2 VR3 VR4
Copy the calculated values for circuits 1 and 2 into the tables
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Lab 5: Basic Electrical Measurements
2. Circuits 1 and 2 Construction
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Build circuit 2 exactly as shown below (bend the brown jumper wires as shown;
these wires are later removed for resistance and current measurements). Resistors
are found in the resistor drawers. If exact value is not available them substitute
the nearest available value, note the new values in the procedure, and use this
device’s measured value in all relevant calculations.
R1
R3
J1
J2
R2
J3
R4
Figure 3: Circuits 1 and 2
3. Resistance and Voltage Measurement using the Multimeter
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Locate the Agilent 34401A Digital Multimeter
Press the white Power button to turn on the multimeter
Confirm that the gray Terminals button is out (i.e., the front terminals are active)
o Note that there are two sets of identical terminals in the front and back of
the multimeter. The rear terminals have probes already plugged in and are
ECE 206
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Lab 5: Basic Electrical Measurements
typically set for voltage and resistance measurements. We will use the
front terminals for today’s lab, so the button is out
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Connect a pair of red and black test leads to the multimeter as shown below for
resistance and voltage measurements:
The Digital Multimeter set for Resistance and Voltage Measurements
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Press the white  2W button to select the resistance measurement mode
Briefly clip the two test leads together (The multimeter reads approximately zero
Ohms. Always test the probes before relying on them!)
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To make resistance measurements with the multimeter:
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Remove the jumper wire (J3) from between R3 and R4
Clip the red test lead to either of the legs of resistor R1
Clip the black test lead to the other leg of R1
Record the resistance value shown on the multimeter in your lab notebook
(e.g., 471.92 Ohms will read as .471.92KOHMS)
o Unclip the two test leads from R1 and repeat the measurement for the
other 3 resistors
o Unclip the two test leads from the last resistor measured, and set them
aside
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Locate the Agilent E3631A Triple DC Power Supply
Press the white Power button to turn on the power supply
To set the power supply to +10VDC:
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Press the Output On/Off button to enable the power supply output
Press the +25V button to select the +/- 25V power supply
Turn the ADJUST dial clockwise until the display shows “10.00V”
Press the Output On/Off button to disable the power supply output
Connect the second pair of red and black test leads between the power supply and
the circuit as shown below:
The Power Supply Connected to the Circuit
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Press the power supply’s Output On/Off button to provide power to the circuit
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To take DC voltage measurements of R1 and R2 with the multimeter:
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Lab 5: Basic Electrical Measurements
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Press the DC V button to select the DC voltage measurement mode
Clip the red test lead from the multimeter to one leg of R1
Clip the black test lead from the multimeter to the other leg of R1
Record the voltage drop VR1 in your table (a negative voltage means that
you have the probes reversed from the correct polarity-change them!)
o Repeat the voltage measurement for R2
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Measure the circuit input voltage by connecting the multimeter test leads to the
same points where the power supply is connected to the circuit. Record the value
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Press the Output On/Off button to disable the power supply output
Unclip the multimeter test leads from the circuit
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Reinstall jumper wire J3 to complete circuit 2
Press the power supply’s Output On/Off button to provide power to the circuit
Take voltage measurements of the resistors in circuit 2 using the same procedure
as above (be sure to include R1 and R2, since the voltages are different from those
in circuit 1)
Measure the circuit input voltage for circuit 2, and record the value
Press the Output On/Off button to disable the power supply output
Unclip the multimeter test leads from the circuit
4. Current Measurement using the Multimeter
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Do not make voltage measurements while the multimeter is set for current
measurements-you will blow the current limiting fuse!
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To make DC current measurements with the multimeter:
o Remove the red test lead from the V input on the front panel
o Connect the red test lead to the I input (below the black test lead
connection)
o Press the blue Shift button, followed by the DC I button
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Remove jumper wire (J3)
Remove jumper wire (J2)
Clip the red test lead of the multimeter to the left leg of R3
Clip the black test lead of the multimeter to the top leg of R2 (the multimeter is
now ready to measure the series current for circuit 1)
Press the power supply’s Output On/Off button to provide power to the circuit
Record the current shown on the multimeter for IR1/IR2 of circuit 1
Press the Output On/Off button to disable the power supply output
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Lab 5: Basic Electrical Measurements
Reinstall jumper wire (J3)
Press the power supply’s Output On/Off button to provide power to the circuit
Record the current shown on the multimeter for IR2 of circuit 2
Press the Output On/Off button to disable the power supply output
Unclip the multimeter test leads from the circuit
Reinstall jumper wire (J2)
Remove jumper wire (J1)
Clip the red test lead of the multimeter to the right leg or R1
Clip the black test lead of the multimeter to the left leg of R3
Press the power supply’s Output On/Off button to provide power to the circuit
Record the current shown on the multimeter for IR1 of circuit 2
Press the Output On/Off button to disable the power supply output
Unclip the multimeter test leads from the circuit
Reinstall jumper wire (J1)
Remove jumper wire (J3)
Clip the red test lead of the multimeter to the right leg or R3
Clip the black test lead of the multimeter to the top leg of R4
Press the power supply’s Output On/Off button to provide power to the circuit
Record the current shown on the multimeter for IR3/IR4 of circuit 2
Press the Output On/Off button to disable the power supply output
After all the measurements are recorded, disconnect the test leads from the circuit
and turn off the equipment. You are done!
Before leaving the lab, take a few minutes to make sure all equipment and test leads are
returned to your cabinet, and then lock it. Return the cabinet key to your T.A. Pick up
any loose parts on the workstation table, and wipe off any eraser shavings, or other debris
with a paper towel. Dispose of the paper towel and debris in the wastebasket.
4. Capacitor Voltage Measurements using DMM
This experiment will demonstrate how parallel capacitors sum their capacitance and how
voltage divides between series capacitors.
Capacitors connected in parallel result in a capacitance equal to the sum of their
individual capacitance. Cp = C1 + C2
Capacitors connected in series result in a capacitance equal the inverse of the sum of the
inverse of their individual capacitance. Cs = 1/( (1/C1) + (1/C2) ).
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Lab 5: Basic Electrical Measurements
Parallel Capacitors have the same voltage across each capacitor.
Series Capacitors divide the voltage between them such that, the voltage on a capacitor is
proportional to the total capacitance divided by the capacitance of capacitor with the
voltage of interest. VCx = Vs(Cs/Cx).
Before starting calculate the expected values for the voltage readings for circuit 3. Show
your work in the report and record the values in the results table. V1 reading and the
Vc3, voltage across capacitor 3 in circuit 3. Also Calculate the Voltage on C3 if C1 were
removed. Build Circuit 3 on the ELVIS II+ prototype board
Figure 4: Circuit 3 Parallel/Series Capacitor Circuit
Step 1: select and measure 3, 1 μF Capacitors ( or a set of Capacitors Near 1μF) and a 1
MΩ resistor
Step 2: record the capacitances values and keep track of which cap has which value.
Step 3: Build Circuit 3, figure 4, on the lower left of the ELVIS prototype board, but we
will use the Agilent Multimeter to make our measurements.
Step 4: Start the ELVIS II+ software and from the NI ELVISmx Instrument Launcher,
launch the Function Generator, FGEN.
Step 3: Connect the ELVIS Function Generator to you circuit as shown using jumper
wires from row 33 of the lower terminal strip to the top of the two parallel capacitors and
the ground from row 53.
Step 4: Connect the black lead of the Agilent 34401A Multimeter to the circuit 3 ground
and the red (VΩ [diode]) lead to the top of the parallel capacitors where the Function
Generator is connected.
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Lab 5: Basic Electrical Measurements
Figure 5: Capacitor Measurements & Function Generator Connection
Step 5: Turn ON Power to the Agilent meter and press the ACV button (second button
from the left top row) This will read TRUE RMS.
Step 6: On the NI ELVISmx Function Generator window:
a. Click the sine wave button (top left button)
b. Set the frequency to ~ 60 Hz
c. Set the Amplitude to 10 Vpp
d. Set the DC Offset to 0 V
e. Set Modulation Type to None
f. Set Signal Route to “Prototyping Board”
g. Click the Run button
Step 7. Turn ON to the ELVIS Prototype Board.
Step 8: Read the Agilent Meter Display for the Vs, source voltage, and record the value
Step 9: Move the Red Agilent Meter lead to the top of C3 and read the C3 capacitor
voltage. See Figure 6.
Figure 6: Measurement Connections for Cap 3 Voltage.
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Lab 5: Basic Electrical Measurements
Step 10: Record the reading in the results table.
Step 11: Turn OFF the Prototype Board Power Supply.
Step 12: Remove Capacitor 1 ,C1,
Step 13: Turn On the Prototype Board Power Supply
Step 14: Read the New Voltage across Capacitor 3, C3, from the Agilent Multimeter.
Step 15: Record the reading in the results table.
Step 16: Determine if any of the readings have significant errors and if so track down the
cause.
4. Analysis
Write a Lab Report for this lab. Be sure to also include the following topics:
Compare theoretical vs. measured values. Are there differences? If so, why?
What are some types of errors possible when making measurements with a DMM? (see
the back of the Agilent Multimeter User Manual.
Explain any difficulties you had with this lab. (Please include suggestions to improve the
lab, if you have them).
Updated 02-12-13 by David Modisette: