NEW MEXICO STATE UNIVERSITY
Electrical & Computer Engineering Department
EE 162L
Digital Circuit Design
Fall 2012
Lab 0: Introduction to Lab Equipment/Proof of Ohm’s Law
(September 4, 5, 6)
OBJECTIVES:
• To become familiar with lab equipment: to use it correctly, effectively, and safely
• To interpret circuit diagrams & correctly prototype/breadboard a simple circuit
• To prove Ohm’s Law
• To learn how to keep neat, detailed notes & interpret data for reports
EQUIPMENT REQUIRED:
Blue or black pen
Lab Notebook
Calculator
DC Power Supply (with connection cables)
Multimeter (with probes)
Oscilloscope (with probes)
Function Generator (with connection cables)
Assorted Resistors
Breadboard
Small, flat-head screwdriver
(You will only be responsible for bringing the italicized items to this lab.)
PREPARATION:
Look up the datasheets for the equipment that will be used (model numbers given
below) and read about the various functions.
Tektronix TDS3012 (100MHz, 1.25GS/s) Oscilloscope
Tektronix CFG280 (11MHz) Function Generator
Hewlett Packard 6218A DC Power Supply
Purchase lab notebook (from NMSU Bookstore, Staples, or other office store); number
notebook pages if necessary, leave 2 pages for table of contents.
LAB EXERCISE:
I.
The first part of lab, your TA will be talking to you about each piece of equipment
you will be using, what its function is, and how to use it safely and accurately. You are
encouraged to ask questions and take detailed notes in your lab books to refer to later.
II.
There are two main “stations” in this lab: Power and Signals. You will need to
spend time at both stations and complete the tasks for each one to receive full credit for
the lab.
After your TA is done going over all the equipment, you will have several minutes in
which you and a partner will be given an opportunity to sit down and use the equipment
to perform the required tasks. At the end of the several minutes, each student will be
tested individually on the functioning of the equipment and their knowledge of Ohm’s
Law.
You will then swap spots (so if you were in the “Power” section, you will move to the
“Signals” station, and vice versa), and the process will be repeated.
A.
Power Station (DC Power Source, Multimeter)
1.
Identify, draw, and label the Power Source controls, briefly detailing the
function of each control.
Q: How many cables do you hook up to the power supply to use it in your
circuits? Why?
2.
Start with the Voltage at 0V (the “Voltage” knob turned all the way counterclock-wise) and hook up the supply to the Multimeter. Do NOT turn on the
supply yet! Have your TA check the wiring first.
Q: Which position should the Multimeter probes be in (in which holes)? Draw
and label.
3.
Activate the Multimeter, and then activate the supply. Try slowly adjusting the
voltage up and down between 0V and 15V. Observe and compare the
readings from the needle indicator on the supply and the readings from the
Multimeter. Deactivate the supply and Multimeter, and then disconnect your
setup.
4.
Use a Multimeter to measure a provided Resistor. Compare your
measurement to the colored band label on the resistor (search online for
“resistor color code” and decrypt the resistor’s marked value from that).
Q: What position were your Multimeter probes in for this section? Was the
resistor’s measured value close to the marked value?
5.
Interpret and construct (on your own breadboard) the circuit seen below:
Have your TA check your circuit before you activate the power supply!
6.
Measure the voltage across the Resistor using a Multimeter.
Q: Is it what you expected? Why or why not?
7.
Rewire your circuit to include the Multimeter, AFTER you set up the probes to
measure current:
Q: Is the Multimeter in series or in parallel with the resistor?
8.
Have your TA check the circuit, and then activate the circuit. Measure the
current as read by the Multimeter.
9.
Use Ohm’s Law to calculate the Resistor’s value, based on the voltage you
read in step 6 and the current from step 8. (You are assuming the Multimeter
has 0 Ohms resistance, like a wire.)
10.
Tell your TA you are ready for testing. He will give each of you a resistor and
allow you to choose a voltage to set the Power supply at. You will then
demonstrate proper use of a Multimeter to measure current, and then use
Ohm’s Law to determine the Resistor’s value. You will receive only 2 tries to
get the value right. Your TA must be present during the test and must sign off
on your lab sheet once you get the correct answer, or you cannot get full
credit!
B.
Signals Station (Function Generator, Oscilloscope):
1.
Take a few moments to identify the controls on the Oscilloscope (O-Scope)
and Function Generator.
2.
Attach a scope probe to channel 1 on the O-Scope and then turn on the OScope. After it has warmed up, it will be time to compensate the probe. This is
done by adjusting a variable capacitor in the probe itself.
3.
Locate the test signal output on the O-Scope (the TA should have gone over
where it is), then attach the probe’s ground clip to the ground pin of the test
signal generator. Finally, attach the positive end of the probe to the positive
pin of the test signal generator. Press “Autoset.”
Q: What do you see on the O-Scope screen? Draw it.
4.
If the signal on the screen is not a perfect square wave, the probe needs
compensating. Use the small, flat-head screwdriver provided to adjust the
capacitor on the probe. Ask the TA if you are unsure of where the capacitor
is. Turn the screwdriver gently and slowly until the signal on the screen is a
perfect square wave.
5.
Hook up the cable with alligator clips to the Function Generator on the “Main
Out” connection on front. Turn the amplitude knob all the way counter-clockwise; we will ease the amplitude up slowly.
6.
Connect the ground of the O-Scope probe to the ground of the Function
Generator, and then connect the positive lead of the O-Scope to the positive
lead of the Function Generator. (Remember, the standard convention is for
positive to be red and ground to be black.) Have your TA check your
connections.
7.
Activate the Function Generator, and then slowly turn the amplitude up (no
more than a quarter turn). If you cannot see the signal on the screen, press
the O-Scope’s “Autoset” button.
8.
Take a few minutes to adjust the frequency and amplitude knobs on the
Function Generator and observe the changes on the O-Scope. Also, adjust
the amplitude “Scale” knob and time “Scale” knob on the O-Scope to see how
it changes your view of the waveform.
9.
Learn how to operate the cursors on the O-Scope. Press the “Cursor” button,
and then select either “H Bars” or “V Bars” (know how to use both!). Two lines
will appear on your screen. Use the multiuse knob (ask your TA where this is)
to change the position of one of the lines. Then, press “select” to select the
other line and turn the multiuse knob to change the position of the second
line.
Q: What value or variable will the vertical lines (V Bars) measure? What about
the horizontal lines (H Bars)?
10.
Use the cursors to measure the period (or frequency) and amplitude of the
output signal of the Function Generator. The O-Scope is set up such that it
will display the difference (delta) between the two cursor lines, whether they
are vertical or horizontal.
11.
Shut off the Function Generator, and then the Oscilloscope. Disconnect your
setup, and then signal your TA that you are ready for testing. He will ask each
individual student to set up the Function Generator and O-Scope again, to set
the Function Generator to a certain shape, frequency, and amplitude, and
then accurately measure it on the O-Scope using the scaling knobs and
cursors. You will receive only 2 tries to get the setup right. Your TA must be
present during the test and must sign off on your lab sheet once you get the
correct answer, or you cannot get full credit!
LAB REPORT:
You will need to include the “TA Verification Lab Cover Sheet” or you will receive no
credit for your report.
There was no pre-lab for this week’s exercise, but there was some preparation work
needed. In a few sentences, discuss what you did to get ready for the lab. Were there
any preparations you wished you had done that would have made the lab easier?
Steps/Questions: For each step, briefly (around 2 or 3 sentences), describe what you
observed in each step during the lab based on the notes you took in your lab notebook.
Include graphs, drawings, tables etc. if you believe it will help explain what you did/saw
(you can scan your lab notebooks to get the graphs; don’t tear out pages).
In addition to these specifications, you will also need to complete and include all the
sections specified by the professor in his “lab report requirements” link on the course
website. All typed reports are due at the beginning of the next lab.