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EGR 101 Resistance Lab

EGR 101 Resistance Lab. Read this before class on Tuesday. Reminder about Teaming. Share the technical load Make sure each team member understands what’s going on. Digital Multimeter (DMM). Used to measure the following : Voltage – DC and AC Current – DC and AC Resistance Capacitance

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EGR 101 Resistance Lab

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  1. EGR 101Resistance Lab • Read this before class on Tuesday

  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%)

  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 Table Generated by Excel Raw Data Number of resistors with values < or = to 900 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 = • 1.8 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: 450-510 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 = = = 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 400-800, 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

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