1. EGR 101 Resistance Lab
Read this before class on Tuesday 9/18

2. Reminder about Teaming
Share the technical load
Make sure each team member understands what’s going on

3. Digital Multimeter (DMM)
Used to measure the following:
Voltage – DC and AC
Current – DC and AC
Resistance
Capacitance
Temperature – w/ extra probe
Also used to check:
Diodes
Transistors

4. Today We’ll Use the DMM to Measure Resistance
Resistors restrict the flow of current, given a fixed voltage
Unit = Ohms, Ω
They come in different packages

5. Color Code
The resistors we’ll test today have a color code to identify their resistance and tolerance.

6. Resistor Color Band Code
Band 1 (closest to the end) – first digit
Band 2 – second digit
Band 3 – power of ten multiplier (most cases simply the number of zeros)
Band 4 – tolerance (Red = 2%, Gold = 5%, Silver = 10%, none = 20%)
Color
Value
Black
Brown
Red
Orange
Yellow 1 2 3 4
Green
Blue
Violet
Gray
White 5 6 7 8 9

7. What is “Tolerance” about?
If a resistor has a nominal value of 1000 Ω and a tolerance of ± 10 % then individual resistors with the same nominal value are allowed to vary in their actual values from 900 Ω to 1100 Ω and still be considered acceptable.
Any resistor fabricated with an actual value outside that range should be rejected as “not meeting specifications”.

8. Ultimate Goal of this Lab
To generate a histogram demonstrating how many of your resistors meet specifications.
A histogram is a plot that shows how many of an item fall into specific bins.

9. Example Histogram Raw Data Table Generated by Excel
Value 1
1000 2
1050 3
990 4
1075 5
950 6
899 7
1102 8
1080 9
1005 10
1020
Number of resistors with values < or = to 900
Bin
Frequency
900 1
950
1000 2
1050 3
1100
More
Number of resistors with values from 1051 through 1100
Plot of Excel Table Data

10. Practice Problems Brown Blue Red = Yellow Violet Gold = 33 k Ohms =

11. Resistance Lab – Part 1 (45 minutes)
Each team will be given a package of resistors.
For each resistor,
Determine the expected value of resistance by applying the color code.
Measure the actual value of the resistance by using the ohmmeter function on the Digital Multimeter.
Compare the actual and expected values of resistance – does the actual value fall within the allowable range?
Enter your results in an EXCEL table, as shown on the next page.

12. Data for Resistance Lab – Part 1
Names: Team #
Eg: Ohms
100*(Meas-Nom)/Nom
Determined from color band code
Leader: Timekeeper: Recorder:

13. Resistance Lab – Part 2 (55 minutes)
Each team will be given a sample of resistors having the same nominal value.
For each resistor:
Determine the nominal value from the color code.
Measure and record the resistance of each resistor in the sample.
Enter your data in an Excel table (sheet 2) as shown on the next page.
Plot a histogram bar graph of the measured values and determine the mean and the standard deviation of the resistance values.

14. Data for Resistance Lab – Part 2=
Explain Allowable range, mean and standard deviation
Leader: Timekeeper: Recorder:

15. Preparing to Plot a Histogram
Before you start to generate a plot, generate a sequence of 5 numbers in your Excel sheet, equally spaced, from the minimum of your allowable range to the maximum of your allowable range.
For example, if my range was , I would generate the following sequence:
400
500
600
700
800

16. Generating a Histogram Table
Click on the “Tools” pull-down menu
Select “Data Analysis”
(If you don’t see Data Analysis, click Mcrosoft logo, click excel options at the bottom, select “Add-Ins” and then select “Analysis ToolPak”)
Select “Histogram”
For Input Range
Enter the cell range with your resistance measurements (e.g. a4:a20)
For Bin Range
Enter the cell range of your 5 values
For Output Range
Enter the cell that you want to be the upper left corner of your histogram table

17. Generating a Histogram Plot
Select (click and drag the cursor over) the table that was created using the histogram command
Click on the “Insert” pull down menu
Select “Chart”
Select “Column” chart type (default), click “next”
You’ll see a preview of your plot, click “next”
Enter a label for the x axis and change the plot title from “frequency” to something with your nominal resistor value in it, click “next”
Select “as object in sheet 2” in last step then click “finish”

18. What needs to be turned in:
Everyone's practice problems
A printout of the data table from the 1st experiment
A printout of the data table from the 2nd experiment including:
The original data
The histogram table
The histogram plot
Each participating team member needs to print and sign his/her name