ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
OBJECTIVES

Learn how to connect I/O signals and components to a myDAQ

Learn to read resistor color codes, schematics, and how to wire a protoboard

Learn to use the ammeter, ohmmeter, voltmeter, and I/O ports on the myDAQ

Verify Ohm’s Law

Learn how to connect and measure the characteristics of series and parallel circuits

Learn to calculate power loss in resistors
EQUIPMENT REQUIRED






Protoboard---- students must provide their own. Contact SCETA 9-257 for availability.
Two banana cables---- students must supply their own
One lot of clip leads---- students must supply their own clip leads
National Instruments myDAQ---- supplied by ECE Department
One lot of resistors ----available in the 5th floor stock/supply lab. The ratio of the smallest
resistor to the largest should be less than 5 is suggested.
One lot of small solid wires---- AWG 20 through 24 (insulated solid wire not stranded) for
connecting to the myDAQ terminals
PRELAB

Read the NI myDAQ User Guide and Specifications. See the website below. Also, watch the NI
training videos shown below. YouTube has numerous videos on the myDAQ.
National Instruments myDAQ training websites and other training videos
There are numerous training websites on YouTube and the National Instruments website.
myDAQ manual and specifications http://www.ni.com/pdf/manuals/373060e.pdf
Read the manual and familiarize yourself with the capabilities and limitations of the myDAQ
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Learning objectives

Know the voltage and current limitations of the various terminal ports. The myDAQ has an
internal fuse that will blow if the current exceeds 1 ampere to the ammeter terminals. Make
sure the input voltage to the voltmeter does not exceed 60 volts. Review all of the limitations
for the 20 I/O terminals.
Learn the uses of the 12 instruments on the NI ELVISmx Instrument Launcher. Some of the instruments
can only be used by writing virtual Instruments (Vis) in LabVIEW which is available on all of the
computers.
Please watch either of the following videos before the laboratory class. They are identical videos.
http://www.bing.com/videos/search?q=myDAQ+tutorial&FORM=VIRE1#view=detail&mid=A7BA099657
6D8094D660A7BA0996576D8094D660
https://www.youtube.com/watch?v=RsD2tHbuAF4&list=PL727B195319D722ED&index=1

Understand how to build a circuit on a protoboard.
https://www.youtube.com/watch?v=oiqNaSPTI7w
https://www.youtube.com/watch?v=Mq9XMNsoAd8
https://www.youtube.com/watch?v=q_Q5s9AhCR0
Figure 1-1 is a block diagram of the myDAQ internal circuitry. See the reference manual for the input,
output, and power limitations of the myDAQ.
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Figure 1-1. Block diagram of the myDAQ internal circuitry.
BACKGROUND
Reference directions for voltage, current, and power are not arbitrary. All meters that measure these
parameters are designed to meet international standards. For example, if you are going to attach a set of
jumper cables between a car with a charged battery and a car with a dead battery, it is extremely
important that the cables be connected in accordance with the established standards. If the batteries are
accidentally reversed there could be an explosion of one or both batteries resulting in a fire and serious
damage to the cars. The jumper cable that is red is connected to the positive terminal of each battery.
The jumper cable that is black is connected to the negative terminal of each battery. This same color code
is used on ammeters, multimeters, power meters, and various other instruments used in industry. This is
no different than measuring the elevation of points on the ground. It is well understood what is up and
what is down. The same principle applies to voltages. It is necessary to understand whether a voltage is
above or below a reference voltage. When you see a stream flowing in the mountains you know what is
upstream and what is downstream. The same principle applies to currents and a wire. The only difference
is that you can't see voltages and you cannot see currents and so you have to rely on your instruments.
Make every effort to make your measurements so that voltages and currents are typically positive. For
example if you live in Los Angeles and wish to drive to San Bernardino you would not tell a driver to drive
minus West to go from Los Angeles to San Bernardino. So why would an engineer say that he has a battery
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
with a negative voltage or a wire with a negative current. Civil engineers wouldn't tell a hiker to go minus
uphill to reach a destination which is downhill from the hiker. The accepted standards for voltage and
currents are shown in Figure 1-1. If the product of V and I is positive then the circuit in the box is a LOAD
(for example a resistor). If the product is negative then the circuit in the box is a source (for example a
battery). Notice in the figure that if a positive current goes into the positive voltage terminal then the
circuit is a load otherwise it is a source. If a current is going into the positive terminal of your car battery
then the battery is a load and it is being charged by your alternator or a battery charger.
If your measuring instrument reads negative, then reverse the leads so that it reads positive. DO NOT try
to work with negative numbers. Do not draw a current arrow in one direction and then say that current
is flowing in the negative direction. That is left as a trick question on exams. Don’t be fooled by this
technique. The positive lead on a multimeter is RED. The negative lead is black. If the current reads
negative then the current is LEAVING the red lead. If the voltmeter reads positive, then the red lead is at
a higher potential than the black lead. Short circuits have no voltage, but they can have current. Open
circuits can have voltage, but they do not have current.
i
i
+
Load
-
Load
V
e.g. resistor or
motor
V
e.g. resistor or
motor
i
+
i
+
Source
-
Source
V
e.g. resistor or
motor
V
e.g. resistor or
motor
-
+
Figure 1-2. Reference-Direction Standards for Voltage and Current.
PROCEDURE
Part 1. Activate the myDAQ
1. Turn on the computer and open National Instruments software as shown in Figure 1-3 as
follows:
o Open all programs/ National Instruments, Figure 1-3. Then Open NI Elvismx for
NI ELVIS & NI myDAQ then open NI ELVISmx Instrument Launcher.
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Figure 1-3. Starting the MyDAQ software.
2. Connect the myDAQ to the computer USB port (cable on bench top).
3. You should now see the NI ELVISmx Instrument Launcher on the top of the screen. See
Figurer 1-4. Not all of the Virtual Soft Front Panels (SFP) are accessible directly by the
myDAQ. However, they can all be simulated in LabVIEW which is installed on all of the
computers.
Figure 1-4. NI ElVISxmx Instrument Launcher
Note
The NI Elvis (National Instruments Educational Laboratory Virtual Instrument Suit) is a custom
designed prototyping board that is available for purchasing from NI. They are not available
in the Cal Poly Pomona labs, Figure 1-5(a). This is a complex protoboard that has built-in
power supplies, signal generators, and many other features. We will be using the protoboard
shown in Figure 1-5 (b)
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
(a)
(b)
Figure 1-5. (a) NI Elvis (National Instruments Educational Laboratory Virtual Instrument Suit)
and (b) Protoboard.
In this experiment we will be using the Digital Multimeter (DMM), the left most SFP. We will be
using this panel to measure, resistance, voltage, and current.
Part 2. Measure resistance, voltage and current using the DAQ DMM
BACKGROUND
Resistance Resistors are used for many purposes such as electric heaters, voltage control, and current
control. Resistance values and tolerances vary widely. Resistance tolerances may range from +0.001 to
+20%. The most common types of resistors are carbon composition, wire wound, metal film, carbon film,
steel, and liquid. Their ratings can range from microwatts to megawatts. Variable resistors are called
either potentiometers or rheostats. When used as a potentiometer their output is a variable voltage.
When used as a rheostat they are used to control current. A good reference source for resistor color
codes and other codes is [http://en.wikipedia.org/wiki/Electronic_color_code]. Review this website
before you come to the laboratory. Many types of resistors do not have a color code such as resistors
made to military specifications and surface mount resistors [http://en.wikipedia.org/wiki/Surfacemount_technology]. You might remember the following mnemonic to help you remember the color
versus number code:
Bad (0) Boys (1) Race (2) Our (3) Young (4) Girls (5) But (6) Violet(7) Generally (8) Wins (9).
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White
Typical resistors are shown in Figure 1-6.
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
(a)
(b)
(c)
Figure1-6. Typical Resistors. (a) 1/8 w to 2 W, (b) 5 W to 25 W, (c) 1/32 W . Very small surface
mounted resistors have no markings and you need a microscope to identify them. The resistors
internally in an integrated circuit (IC) are considerably smaller than surface mount resistors.
Colors such as silver, gold and yellow on one end indicate parameters such as tolerance and temperature
ratings. Most through-hole resistors Figure 1-6 (a) use either 4 or 5 bands of colors. The 5 band color is
usually used for 1% and 0.1 % resistors. Surface mounted resistors (SMD) either have a printed code or
no markings Figure 1 (c). Typical wattages and sizes are shown in Table 1-1.
Table 1-1. Surface mount resistors.
Package Style
Size(mm)
Power Rating
2512
6.30 x 3.10
0.5
2010
5.00 x 2.60
0.25
1210
3.20 x 2.60
0.25
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
1206
3.00 x 1.50
0.125
0805
2.00 x 1.30
0.10
0603
1.50 x 0.08
0.0625
0402
1.00 x 0.50
0.0625 -0.031
0201
0.60 x 0.30
0.05
Power When you observe a resistor it is not always possible to predict its wattage by just observing its
size. There are many variables that affect a resistor’s wattage. Some such parameters are size, mounting,
encapsulation, and cooling. There are three ways you can calculate the power being dissipated in a
resistor in this laboratory. See Eq. 1-1. In a thermodynamics' laboratory you could measure the rise in
temperature of water in a calorimeter to determine the power being dissipated by a resistor. Consider
the following design problem. What size (ohms and wattage) resistor would you use for the heating
element in a coffee maker or toaster? Assume 120 VAC and 300 watts.
𝑃=
𝑉2
𝑅
= 𝐼 2 𝑅 = 𝑉∆𝑅 𝐼𝑅
(1-1)
The resistance of a resistor can be approximated by equation (1-2):
Resistance (R)=
𝜌𝐿
𝐴
1-2)
Where 𝜌 =resistivity of the material; L = length of material; and A is the area of the material. The material
may be solid, liquid, or gaseous. Each of these parameters is often functions of temperature and stress.
Temperature The first order approximation of resistance change with temperature is defined by equation
(3).
𝑅 = 𝑅𝑜 (1+∝ ∆𝑡)
(1-3)
Where
Ro is the resistance at 25 oC
= material temperature coefficient, expressed as ohms/oC or ppm/oC ( parts per million).
t is the change in temperature. It is expressed as ohms/oC
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
It is very common to use this characteristic of resistors in the design of temperature sensors. Knowing
the variation of resistance with temperature is extremely important in the analysis and design of
electronic circuits.
Liquid is often used for low resistances rated in the megawatts. It quite often consists of two electrodes
in a tank filled with CaCO3. Some typical resistors are shown in Figure 1-6a.
1. Connect a banana plug to the myDAQ ohm terminals. See Figure 1-7. Make sure that the
banana plug terminal with the nob on the side is plugged into the black terminal of the
myDAQ. See Figures 1-7 and 1-8. This is not important when measuring just resistance;
however, it is very important when making all other measurements.
Figure 1-7. MyDAQ connected to computer and resistor.
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Figure 1-8. Banana plug without cable
2. Select the DMM SFM then select the  function. See Figure7. You can select the Mode
and Range to match the resistance being measured.
Figure 1-9. Using the myDAQ to measure resistance.
3. Measure a total of five (5) resistors and enter their values in Table 1-1. Then complete
the table. Assume the color code is the accurate value and the measured value is in error.
Note that the measured resistance is usually different from the value predicted by the
color code. Resistors typically have a tolerance of 0.1, 1, 5 and 10%
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Table 1-1. Resistor color codes and Error Analysis
Measured
Value ~ Ohms
Color Code
Theoretical
Value from color code ~
Ohms
% error
Experimental
Discrepancy
4. Install the 5 resistors in series on the protoboard. See Figure 10. Do not use any resistor
values less than 100 ohms. We do not want to damage the myDAQ in later steps when
we measure voltages and currents.
5. What was the total resistance of the 5 resistors? _____________ ohms. Measure the
resistance of a couple of the resistors while they are in series.
6. Question Did the values change. __________________
7. Connect 15 volts to the 5 resistors in series using the myDAQ + 15V output on the side
terminals. See Figure 1-10.
Figure 1-10. Connect voltage to five resistors in series.
8. Measure the total resistance of the 5 resistors in series. Then measure the resistance of
each resistance again while they are in the series connection.
Total resistance of the series connection ________________ ohms
9. Question Should all the resistance values remain the same when connected in series?
10. Explain ____________________________________________________
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
11. Measure the voltage across each resistor. See Figure 9. If you reverse the red and black
leads the voltmeter will read (-) negative.
Figure 1-11. Measure voltage across each resistor in series
12. Question. What is the sum of the voltages across each resistor ________?
13. Complete Table 1-2, Series Data for resistors.
14. Measure the current through the series resistors using the myDAQ ammeter. See Figure
11. Break the series circuit anywhere and insert the ammeter.
Figure 1-12. Measure current through the series circuit.
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
15. Question. Does it make any difference where you break the series circuit to measure the
series current? _________________________________________________
Table 1-2. Series Data for resistors
Resistance~ ohms
V
Current=  V/R
Power=  V2/R
Paralle Circuits
16. Connect 5 resistors in parallel. See Figure 1-13. Then complete data for Table 1-3.
17. What is the total power drawn by the parallel circuit. __________________________
Figure 1-13. Measure resistance of 5 resistors in parallel.
18. Connect 15 VDC across the parallel resistors. See Figure 12 and 13.
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Figure 1-14. Applying 15 Volts across 5 resistors in parallel.
19. Measure current through each resistor. See Figure 1-14. You have to disconnect one end
of the resistor when its current is being measured. Current through a 10 K resistor is
shown in figure 1-14.
Figure 1-15. Measuring current through each of the 5 resistors in parallel.
Table 1-3. Data for parallel resistors with a 15 VDC power supply
Resistance ~ Ohms
Current = 15/R
Power = V2/R
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ECE 109 Laboratory Exercise 1
Introduction to the National Instruments myDAQ
Equivalent Parallel R=
 of currents =
 of powers =
Questions
1. What is the difference between conventional current and electron current?
2. For the series circuit of Figure 9, show that the sum of the voltages around the loop is
zero no matter where you start.
3. For the parallel circuit of Figure 11, show that the sum of the currents at either node is
zero. A node is where two or more components connect. Draw a circle around each
node and identify them as Node 1 and Node 2.
Conclusion
Write a professional comprehensive lab report, using a word processor when possible. Show
your results and include a comprehensive conclusion. There are lots of sample lab reports on the
internet. Your report should be such that I can give it to another engineer and they can duplicate
it and verify your findings and conclusion. You can draw schematic drawings and analyze circuits
using PSpice which is available in any of the ECE computer laboratories.
Components of your Lab Report:
1. Names of students in the group that performed the experiment. This is a group report
not an individual report. Reports are due the following week at the beginning of the lab.
2. Title and date of experiment
3. Objective of the experiment
4. Procedure
5. Data and error analysis
6. Answer to the questions
7. Conclusions.
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