ELEC 2010 Laboratory Manual
Experiment 1 - In Lab Procedure
Page 1 of 8
In-Lab Procedure (10 points) and Report (30 points)
Before starting the procedure, record the table # you are working at in your Lab Report. Also record the EE
Inventory # on the orange sticker of any equipment that you use.
(1) Familiarize yourself with the equipment. You will use the Component Box:
and the digital multimeter (DMM):
You will also need a wire tray containing 16 banana plug cables. You should have 4 each of the following:
• longer black cables
• shorter black cables
• longer red cables
• shorter red cables
The color refers to the color of the wire, not the end plugs. (The cable lengths and plug colors vary because when
cables are damaged, our shop personnel repair them by cutting off the bad end and replacing the plugs with available
substitutes.)
If you do not have the proper equipment or the correct wires at your station, let your instructor know.
(2) Your first task will be to perform a continuity test on each of your 16 cables to determine if any are broken.
In the process, you will learn to use the DMM to measure resistance. Follow the indicated procedure below,
and feel free to ask your instructor for help.
(a) Turn on the DMM (left-most red button pushed IN),
(b) set it to DC (next button pushed OUT),
(c) choose to measure resistance (push IN the button marked Ω),
Revised August, 20
ELEC 2010 Laboratory Manual
Experiment 1 - In Lab Procedure
Page 2 of 8
(d) select the lowest range (push IN the leftmost dark brown button marked 200).
Now you are prepared to measure resistance up to 200 Ω (200 ohms).
(e) Select a cable to test. Plug one end of the cable into the HI (red) jack and the other end into the LO (black) jack.
(f) After waiting at least 5 seconds for the reading to stabilize, read the DMM.
A good cable will have an end-to-end resistance less than 1.0 Ω, usually closer to 0.5 Ω or less. If the reading is
within this acceptable range, jiggle the cable and confirm that the reading remains acceptable. This assures that there
are no loose connections at the ends.
If the cable is bad, usually it will be due to an internal “open circuit” (broken wire or bad plug connection). This will
cause the DMM to register an “over-range” indicated by the reading 1. (the digit 1 followed by a decimal point).
However, often the build-up of finger oils and dust on the plugs can cause a poor connection to the DMM, so if you
do not get an acceptable reading at first, rotate the plugs inside the DMM terminals several times, or pull them out
and re-insert them.
If you find a cable you believe to be bad, notify your lab instructor and obtain a replacement.
After measuring all your cables and replacing any bad ones, you are ready for the rest of the experiment.
For your lab report, write a statement such as: “Tested all cables, all were within acceptable resistance range (less
than 1.0 Ω),” or “Performed continuity test on all cables, one was found to be defective and replaced.”
(3) Measuring voltage and resistance: the Component Box.
Measuring Voltage:
(a) Make sure the Component Box is turned OFF using the silver toggle switch on the upper right.
(b) Set the DMM to read voltage (push IN the button labeled V) and set the range to 20 V
(c) Connect the power supply outputs (shown below) to the DMM inputs. Use a red cable to connect the positive voltage
terminal (top) to the HI input, and a black cable to connect the negative terminal (bottom) to the LO input.
Revised August, 2006
ELEC 2010 Laboratory Manual
Experiment 1 - In Lab Procedure
Page 3 of 8
(d) Turn on the Component Box. The power supply should become active, indicated by the lamp. Record the DMM
reading after waiting at least 10 seconds for it to stabilize.
The power supply is marked “12 V” but this is an ideal value. The actual value of your power supply will probably
be less than this, and depends on a number of factors, including the AC voltage at the wall plug, etc. However, if
your reading is less than 11 V, check with your instructor to see if you should replace the Component Box. If you
have a negative reading, your connections to the power supply are swapped.
(e) Now swap the HI and LO cables only at the power supply. Measure and record the DMM reading. Explain this result
in your report. (Answer: The DMM reading should become negative because you have reversed the polarity of the
input.)
Measuring Resistance:
(f) Turn off the power to the Component Box and disconnect the cables to the DMM.
(g) Set the DMM to measure resistance.
(h) Set the DMM resistance range. To do this, look at the resistors labeled R1 through R6 on the Component Box to see
the expected range of values. Set the DMM range to the smallest value that is higher than you expect to measure.
This way, you will get the most precise reading possible (largest number of significant digits).
(i) Measure and record each resistor R1 through R6. If you need to, adjust the range on the DMM for maximum
precision with no over-range. In your lab report, make a table like the one below with all the values filled in.
Resistor
R1
R2
R3
R4
R5
R6
Marked Value
500 Ω
Measured Value
??? Ω
Percent Difference
(see formula)
The equation for percent difference is:
Percent Difference =
MeasuredValue − MarkedValue
× 100%
MarkedValue
(j) Answer in your report: is it true that all the resistor values are within +/- 10% of the marked value?
Revised August, 2006
ELEC 2010 Laboratory Manual
Page 4 of 8
Experiment 1 - In Lab Procedure
(4) Verifying KVL.
Turn off the power to the Component Box and disconnect all cables before proceeding.
(a) Use the Component Box and cables to connect the circuit drawn below.
R3
R1
R2
12 V
R4
A physical drawing of the wiring for this circuit is shown below.
12V
R1
500Ω
R2
500Ω
R3
500Ω
R4
500Ω
R5
500Ω
R6
250Ω
Refer to this drawing while connecting the circuit. It might help you to label each cable in the drawing with a letter
(A,B, C...) and write the corresponding letter on the associated circuit diagram.
Revised August, 2006
ELEC 2010 Laboratory Manual
Experiment 1 - In Lab Procedure
Page 5 of 8
(b) After connecting the circuit, use the DMM to measure and record the voltage drops around LOOP 1 shown below.
Be sure to use the correct polarity. Always connect the DMM (HI) to the “+”-labeled side of the component. Make a
table of measured values in your report.
R1
+ V1 –
12 V
+
VS
–
LOOP 1
+
V2
–
R2
(c) One way to state KVL for this circuit is by summing the voltage drops to zero:
V1 + V2 − Vs = 0
(Since VS is a voltage rise instead of a drop, it has a negative sign.)
In your lab report, calculate the sum of the voltage drops, and compare it to the ideal value of zero. (If your answer is
more than a few tenths of a volt different than zero, you probably made a measurement error, or accidentally got a
polarity wrong. Repeat each measurement until you find the problem.)
(d) Compare your measured value of VS in part (c) to the value you measured in 3(d). In your report, explain why they
are different. (Answer: In this part, the power supply is delivering current to the circuit. Therefore, the magnitude of
its output voltage will drop slightly due to the voltage drop across its own internal resistance (loading effect).)
(e) Verify KVL around LOOP 2 shown below. Measure and record the voltages in a table. Write the KVL equation,
then calculate the sum of the voltage drops and compare it to zero.
Revised August, 2006
ELEC 2010 Laboratory Manual
R1
R3
+ V1 –
12 V
Page 6 of 8
Experiment 1 - In Lab Procedure
+ V3 –
LOOP 2
+
VS
–
+
V4
–
R4
(5) Verifying KCL
Turn off the Component Box power and disconnect the DMM before proceeding.
We will use the same circuit to verify KCL. Now we will measure the currents I1, I2, and I3 entering the node labeled
A , and test whether they sum to zero.
R1
A
R3
I1
I3
I2
12 V
R2
R4
Measuring current is more difficult than measuring voltage. In order to measure current, you must re-wire the circuit
to force the current to flow through the DMM.
Revised August, 2006
ELEC 2010 Laboratory Manual
Page 7 of 8
Experiment 1 - In Lab Procedure
The illustrations on the last page of this write-up show how to make the connections to measure I1. To be displayed
with the correct polarity, the current you want to measure must enter the “HI” terminal of the DMM and leave the
“LO” terminal.
(a) Connect the circuit as shown to measure I1. Set the DMM to measure current (press IN the button labeled “A”).
Select the highest range (2000 mA). Turn on the Component Box power. Maximize the precision of your reading by
selecting the lowest range setting that does not result in an over-range indication. After waiting sufficient time for the
DMM reading to stabilize (at least 10 seconds) measure and record the current.
The value of I1 should be somewhere in the range of +12 mA to +16 mA for this part. The exact value depends on
your power supply voltage and the values of your resistors. If your measurement is not in this range, or if it is
negative, you should re-check your wiring to see if you have made a mistake.
(b) Rewire the circuit to measure I2. Following the same procedure as in (a), measure and record the value. The value of
I2 should be in the range from –10 to –8 mA.
(c) Rewire the circuit to measure I3. Following the same procedure as in (a), measure and record the value. The value of
I3 should be in the range from –3 to –6 mA.
(d) Applying KCL, calculate the sum I1 + I2 + I3 . Verify that the sum is close to zero. If your result is more than 1 mA
different than zero, you should re-check your measurements and calculations.
(6) Verifying Ohm’s Law. Use the voltage measurements you made in 4(b), the current measurements you made in
5(a) and 5(b), and the resistance measurements you made in 3(i) to verify Ohm’s law. In your report, make a table
like the one below and fill in the values from your measurements and calculations.
Resistor
Measured Voltage
Drop (from 4b)
Measured Current
(from 5a,b)
R1
V1 =
I1 =
R2
V2 =
I2 =
* Percent Difference =
Calculated
Resistance =
V I
Measured
Resistance (from
3i)
Percent
Difference*
MeasuredValue − CalculatedValue
× 100%
CalculatedValue
(7) Workstation clean-up.
(a)
(b)
(c)
(d)
Turn off the DMM
Turn off the Component Box
Put all wires back in the wire tray neatly
Discard any trash, and arrange equipment neatly on your table.
Review and Report Completion
Finish writing your lab report, following the outline given in the Course Information. Submit your lab report to your
instructor before leaving the lab.
Revised August, 2006
ELEC 2010 Laboratory Manual
Page 8 of 8
Experiment 1 - In Lab Procedure
DMM
LO
HI
I1
I1
R1
R3
I3
I2
12 V
R4
R2
Measuring the current I1 – Schematic Diagram
DMM
LO
HI
I1
I1
12V
R1
500 Ω
R2
500Ω
R3
500 Ω
Measuring the current I1 – Physical Wiring Diagram
Revised August, 2006
R4
500
ELEC 2010 Laboratory Manual
Experiment 1 - In Lab Procedure
Extra Page
How to read the color code of a resistor
First find the tolerance band, it will typically be gold ( 5%) and sometimes silver
(10%).
Starting from the other end, identify the first band - write down the number
associated with that color; in this case Blue is 6.
Now 'read' the next color, here it is red so write down a '2' next to the six. (you
should have '62' so far.)
Now read the third or 'multiplier' band and write down that number of zeros.
In this example it is two so we get '6200' or '6,200'. If the 'multiplier' band is Black
(for zero) don't write any zeros down.
If the 'multiplier' band is Gold move the decimal point one to the left. If the
'multiplier' band is Silver move the decimal point two places to the left. If the
resistor has one more band past the tolerance band it is a quality band.
Read the number as the '% Failure rate per 1000 hour' This is rated assuming full
wattage being applied to the resistors. (To get better failure rates, resistors are
typically specified to have twice the needed wattage dissipation that the circuit
produces).
Resistor Color Code Guide
Revised August, 2006