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EGR 101 Resistance Lab Read this before class on Tuesday

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Reminder about Teaming Share the technical load Make sure each team member understands whats going on

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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

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Today Well Use the DMM to Measure Resistance Resistors restrict the flow of current, given a fixed voltage Unit = Ohms, They come in different packages

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Color Code The resistors well test today have a color code to identify their resistance and tolerance.

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ColorValueColorValue Black Brown Red Orange Yellow 0123401234 Green Blue Violet Gray White 5678956789 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%) Resistor Color Band Code

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

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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.

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Example Histogram R#Value 11000 21050 3990 41075 5950 6899 71102 81080 91005 101020 BinFrequency 9001 9501 10002 10503 11002 More1 Raw Data Table Generated by Excel Plot of Excel Table Data Number of resistors with values < or = to 900 Number of resistors with values from 1051 through 1100

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Practice Problems Brown Blue Red = Yellow Violet Gold = 33 k Ohms = 1.8 Ohms =

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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.

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Data for Resistance Lab Part 1 Names:Team # Determined from color band code Leader:Timekeeper:Recorder: Eg: 450-510 Ohms 100*(Meas-Nom)/Nom

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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.

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Data for Resistance Lab Part 2 ====== Leader:Timekeeper:Recorder:

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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

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Generating a Histogram Table Click on the Tools pull-down menu Select Data Analysis (If you dont 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

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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 Youll 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

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