Download ECE1250F14_Lab1_MeasR CMF

ECE 3300 Lab 2
ECE 1250 Lab 1
Name _________________________ Lab Section ___ Student Folder # ____
(To find your student folder #, go to the grade sheet and look on the first
column)
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.
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 (that is
best) or during the lab.
o Breadboard (also called a protoboard) & 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 (AAA,AA,C,D)
 Print out this handout and bring it with you. WRITEUPS can be done directly
on this handout, with additional pages attached as needed.
TURN-IN Turn your completed handout in to your TA at the end of the lab, OR
scan it and upload it as a PDF online (see ‘Genius Scan’ utility for your iphone),
OR turn in a hardcopy later to the hand-in locker for your lab (it is next to the one
for your homework).
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
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
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.
Prelab: Watch Lab 1 videos (5 points)
1. Watch the videos posted under lab 1.
WRITEUP: Take notes on the back of this page (or elsewhere) 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:
R = ______________ ohms Colors: ____________________
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):
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
(𝑅𝑚 − 𝑅𝑛)
𝑋 100
𝑅𝑛
where Rm = measured value, and Rn = nominal (or expected) value.
% 𝐸𝑟𝑟𝑜𝑟 =
WRITEUP: Record the following.
Table 1: Resistor color code, expected, and measured values
Color
Band1
Color
Band2
Color
Band3
Color
Band4
Expected
(Nominal)
Value Rn
(ohms)
Expected
%
Tolerance
Measured Measured
Value Rm % Error
(ohms)
(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: Table 2: Potentiometer screw positions and measurement
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.
WRITEUP: Describe how a breadboard is
used, and what you learned about the
breadboard.
Figure 1 Breadboard front (left) and back (right)
2. Measure resistors in series and parallel
a. Use the 1k and 1.5k resistors. Connect them in series, using the breadboard.
WRITEUP: Sketch the breadboard connection and also the circuit
representation. Calculate and measure the series combination and compare
them.
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 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
𝑉2
P=V*I=V*(V/R) = 𝑅 by measuring the voltage V across each resistor. Note the
values and make sure it is less than 0.25W.
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
c. Connect them in parallel, using the breadboard.
WRITEUP: Sketch the breadboard connection and also the circuit
representation. Calculate and measure the parallel combination and compare
them.
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
𝑉2
P=V*I=V*(V/R) = 𝑅 by measuring the voltage V across each resistor. Note the
values and make sure it is less than 0.25W.
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
ECE 1250 LAB 1
e. Now use any combination of your resistors to create the largest possible
resistance.
WRITEUP: Sketch it. Calculate the expected value, and compare it to your
measurements.
f. Now use any combination of your resistors to create the smallest possible
resistance.
WRITEUP: Sketch it. Calculate the expected value, and compare it to your
measurements.
7
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
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 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.
8
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
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 notes.
9
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