EGR 101 Resistance Experiment READ this before class

EGR 101 Resistance Experiment • READ this before class on Thursday 1

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

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 3

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 4

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

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 0 1 2 3 4 Green Blue Violet Gray White 5 6 7 8 9 6

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”. 7

Ultimate Goal of this Exercise • 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”. 8

Example Histogram Table Generated by Excel Raw Data R# 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 Number of resistors with values from 1051 through 1100 Bin Frequency 900 1 950 1 1000 2 1050 3 1100 2 More 1 Plot of Excel Table Data 9

Practice Problems • • Brown Blue Red = Yellow Violet Gold = 33 k Ohms = 1. 8 Ohms = 10

Resistance Experiment – 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. 11

Data for Resistance Lab – Part 1 Names: Team # Eg: 450 -510 Ohms Determined from color band code Leader: Timekeeper: Recorder: 100*(Meas-Nom)/Nom 12

Resistance Experiment – 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. 13

Data for Resistance Lab – Part 2 = = = Leader: Timekeeper: Recorder: 14

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 15

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 Tool. Pak”) • Select “Histogram” • For Input Range – Enter the cell range with your resistance measurements (e. g. a 4: a 20) • 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 16

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” 17

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 18