ECE 3300 Lab 2
ECE 1250 Lab 1
Measuring Resistance and Resistive Networks
Overview: This is your first ECE lab! Please install the MyDAQ on your
computer before you come. If you get stuck, bring your MyDAQ to lab with you
anyway. You don’t need to know anything about electrical engineering before
you start, so just come to lab. Bring the equipment below with you. You need to
write in your lab notebook as described in the separate file about lab procedures
and lab notebooks. Make sure that you have the general section, procedures,
data, and conclusion sections for each subpart within this lab experiment. In
addition, make sure that you include the “Writeup” highlights throughout this
experiment in your lab notebook.
Equipment List:
• MyDAQ board with cables.
• Your laptop (or use the computers in the lab) with Multisim & MyDAQ
software running.
• The following items can be purchased in the ECE Stockroom before or during
the lab.
o Breadboard (also called a breadboard) & wire kit
o Resistors (10, 100, 330, 1.0k, 1.5k, 4.7kohm resistors. You will use
these in later labs as well, so keep track of them.)
o Potentiometers (10k and 100 ohm)
o A battery (any battery is fine)
Instructions & Reference Material:
MyDAQ Resource Page (on ECE1250 website)
• Using the myDAQ Digital Ohmmeter DMM(WΩ):
http://decibel.ni.com/content/docs/DOC-12938
• Measuring Current with a Shunt Resistor and DMM
http://www.youtube.com/watch?v=V6Fv79uVrcw
• Using myDAQ Digital Voltmeter DMM(V):
http://decibel.ni.com/content/docs/DOC-12937
Resistor Color Code (See link on ECE1250 resource page. Available online,
textbook, cell phone app, or hardcopy in the stockroom.)
Safety Instructions: There is very little you can do to hurt yourself or your
equipment in this lab. You can touch and handle all of the parts, including the
MyDAQ, its leads, etc. When you connect the MyDAQ for measuring voltage
and resistance, it has a high input impedance, which means it won’t blow the
fuse, as long as you stay within the specs of the device, which this lab does.
1
UNIVERSITY OF UTAH DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
50 S. Central Campus Dr | Salt Lake City, UT 84112-9206 | Phone: (801) 581-6941 | Fax: (801) 581-5281 | www.ece.utah.edu
ECE 1250 LAB 1
Prelab: Watch Lab 1 videos (5 points)
1. Watch the videos posted under lab 1.
WRITEUP: Notes taken during the videos so you don’t have to go back and
watch them again.
Great ! Your MyDAQ and laptop are working together, so you will be able to build
circuits at home. If you don’t want to have to carry your laptop to lab with you,
you can bring just the MyDAQ, and connect it to the lab computers.
Troubleshooting: When you first use the MyDAQ, the connections for the red
and black leads are a little stiff. Be sure the leads are all the way plugged in to
the MyDAQ. Also see the troubleshooting link on the class MyDAQ page.
If you have problems getting the MyDAQ working with your laptop, we want to
get it working this first week. Bring the MyDAQ and laptop with you, and your TA
can help you get it going. He/she may have you use the lab computers to
complete the lab, and then help you get it going with your computer at the end of
the lab.
WRITEUP: What problems did you encounter, and how did you fix them?
Experiment 1: Measure Resistance (25 points)
1. Use the MyDAQ to measure a resistor, any resistor.
Also measure a short circuit (just touch the black and red leads of the MyDAQ
together), and an open circuit (hold them apart).
WRITEUP: Record the following information in your notebook:
R = ______________ ohms
Short =
Open =
2. Learn about the resistor color codes
From the resistor color code, write the colors of 10 Ω, 100 Ω, 330 Ω, 1k Ω,
1.5 kΩ, and 4.7 kΩ resistors, and determine the % expected tolerance from
the last color band. Find these resistors in your kit and measure them. Also
find the measured % error (which should be less than the expected
tolerance):
𝑅𝑚 − 𝑅𝑛
% 𝐸𝑟𝑟𝑜𝑟 =
𝑋 100
𝑅𝑛
where Rm = measured value, and Rn = nominal (or expected) value.
WRITEUP: Make a table similar to the one below and record the following
information in your notebook:
2
UNIVERSITY OF UTAH DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
50 S. Central Campus Dr | Salt Lake City, UT 84112-9206 | Phone: (801) 581-6941 | Fax: (801) 581-5281 | www.ece.utah.edu
ECE 1250 LAB 1
Color
Band1
Color
Band2
Color
Band3
Color
Band4
Expected
(Nominal)
Value Rn
(ohms)
Expected
%
Tolerance
Measured
Value Rm
(ohms)
Measured
% Error
(should
be ≤
tolerance)
10
100
330
1k
1.5k
4.7k
3. Measure a potentiometer (pot). A pot has three wires sticking out of it, and a
screw to change its resistance. The center wire is always wire 3, and the other
two can be either 1 or 2 (you decide). Measure Rmax, R13, and R23 for
several different turns of the screw on the pot. Sketch the position of the
screw and report the resistances below. What is the maximum and minimum
possible value of R13 and R23? HINT: It will usually be easier to connect the
pot to the MyDAQ by using alligator clips, rather than trying to hold it by hand.
WRITEUP: Note the information above about the pot’s wires in your notebook.
Make a table similar to the one below and record the following information in your
notebook.
Sketch Rmax
R13 (ohms)
R23 (ohms)
(ohms)
R13 min =
R23 min =
R13 max =
R23 max =
WRITEUP: Write a conclusion for this section about measuring resistances.
Note any comments, observations, new skills, troubleshooting steps, etc. not
mentioned previously. Also mention any errors and differences in measurements
and account for the differences.
3
UNIVERSITY OF UTAH DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
50 S. Central Campus Dr | Salt Lake City, UT 84112-9206 | Phone: (801) 581-6941 | Fax: (801) 581-5281 | www.ece.utah.edu
ECE 1250 LAB 1
Experiment 2: Understand the Breadboard (20 points)
1.
The breadboard is a convenient way to build and test circuits (breadtype
them). Closely examine your breadboard, compare it to the front and back
pictures below. Identify the pattern where the holes are connected together
(shorted together by the metal on the back side of the breadboard), and where
they are not. Verify your understanding of how the breadboard is connected by
sticking two wires into the board at various locations and measuring the
resistance. (You know what open circuit (not connected) and short circuit
(connected) resistances are based on your measurements in part II.1 of this lab.
Figure 1. Breadboard front (left) and back (right)
WRITEUP: Describe what you do and what you learned about the breadboard.
2. Measure resistors in series and parallel
a. Use the 1k and 1.5k resistors. Connect them in series, using the
breadboard. Sketch the breadboard connection and also the circuit
representation. Calculate and measure the series combination and
compare them.
WRITEUP: Note that the resistors are in series and sketch their connections,
calculate the expected value, and note the measured value.
4
UNIVERSITY OF UTAH DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
50 S. Central Campus Dr | Salt Lake City, UT 84112-9206 | Phone: (801) 581-6941 | Fax: (801) 581-5281 | www.ece.utah.edu
ECE 1250 LAB 1
b. Your resistors are typically ¼ Watt resistors. For the series circuit in (a)
with a 5V voltage supply, calculate the current, and power across each
resistor. Make sure it is less than 0.25W.
WRITEUP: Redraw the new circuit now with the 5V supply. Calculate the
expected value for current which uses Ohm’s law which is V=I*R where V is the
5V supply, R=values of R in series and then solve for I. Measure the current by
measuring the voltage across one resistor and recalculating the current I using
Ohm’s law again. Calculate the power across each resistor by
!!
P=V*I=V*(V/R) = ! by measuring the voltage V across each resistor. Note the
values and make sure it is less than 0.25W.
c. Connect them in parallel, using the breadboard. Sketch the breadboard
connection (above) and also the circuit representation. Calculate and
measure the parallel combination and compare them.
WRITEUP: Note that the resistors are in parallel and sketch their connections,
calculate the expected value, and note the measured value.
d. Repeat step (b) for the parallel combination in (c).
WRITEUP: Redraw the new circuit now with the 5V supply. Calculate the
expected value for current which uses Ohm’s law which is V=I*R where V is the
5V supply, R=values of R in series and then solve for I. Measure the current by
measuring the voltage across one resistor and recalculating the current I using
Ohm’s law again. Calculate the power across each resistor by
!!
P=V*I=V*(V/R) = ! by measuring the voltage V across each resistor. Note the
values and make sure it is less than 0.25W.
e. Now use any combination of your resistors to create the largest possible
resistance. Sketch it. Calculate it, and compare it to your measurements.
WRITEUP: Sketch circuit that you create and note the values used for the
resistors. Calculate the expected value, and then measure the value.
f. Now use any combination of your resistors to create the smallest possible
resistance. Sketch it. Calculate it, and compare it to your measurements.
WRITEUP: Sketch the circuit that you create and note the values used for the
resistors. Calculate the expected value, and then measure the value.
3. Use the breadboard to connect potentiometers in series.
Many electrical devices are controlled by dials, and these dials are often
potentiometers. The variable resistance, controlled by the dial, controls some
other parameter of interest in the circuit. We are going to use two
5
UNIVERSITY OF UTAH DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
50 S. Central Campus Dr | Salt Lake City, UT 84112-9206 | Phone: (801) 581-6941 | Fax: (801) 581-5281 | www.ece.utah.edu
ECE 1250 LAB 1
potentiometers as a set of coarse and fine dials for a variable voltage source.
The variable voltage is adjusted by the resistance, so the variable resistance
of the pots will basically be used to ‘dial in’ a voltage. We will use a 10kohm
pot as the coarse adjustment dial, and the 100 ohm pot as a fine adjustment
dial. The two pots will be in series. Sketch (below) how you could connect
your potentiometers (in series) so that you can have a maximum resistance of
approximately 10.1kohms, and a mimimum resistance of about 0 ohms,
depending on how you set the two dials.
100Ω pot
10kΩ pot
3
3
Figure 2. Two pots to be connected in series.
Now build this connection of two pots in series on your breadboard, and verify it
(measure the resistances). This means the following connections must be made
using the myDAQ and breadboard:
+5V on myDAQ connects to pin 2 on the first pot
pin 3 of the first pot connects to pin 2 of the second pot
pin 3 of the second pot connects to GND next to the +5V on myDAQ
HINT: This should look similar to the two pots in series shown in Figures B.2 and
B.3 of your lab manual. It may be slightly different, because you may not have
exactly the same kind of pots shown in the manual.
Rmin =
Rmax =
WRITEUP: Sketch the circuit that you create and measure the values for Rmin
and Rmax.
WRITEUP: Write a conclusion that describes what you learned from the
experiments. Discuss any results/data that was collected and anything of note
that wasn’t mentioned as you proceeding through the experiments. (i.e. how
close were the expected results to the calculated values? How close were
measurements obtained by different methods to each other? How accurate were
your results? Account for differences and errors by explaining your observations
in detail. How well did things work? Did you learn any troubleshooting skills or
new skills? Make sure to describe them so you can refer back to your notebook.
6
UNIVERSITY OF UTAH DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
50 S. Central Campus Dr | Salt Lake City, UT 84112-9206 | Phone: (801) 581-6941 | Fax: (801) 581-5281 | www.ece.utah.edu