ECE 211 Electrical Circuits Lab I
LAB #1
Fall 2013
Name ___________________
Section ______________
The Resistor Lab
OBJECTIVE:
1.
2.
3.
4.
5.
Determine the nominal value of the resistance using the color code
Measure the actual value of the resistor using the ohmmeter
Measure the value of the resistor using an alternative technique
Obtain the relationship between V and I in a resistor
Determine if a resistor is within the tolerance
COMPONENTS AND EQUIPMENT:
1. Digital multimeter
2. Leads
3. 12-color-coded resistor
RESISTORS:
As discrete components, resistors come in various sizes and shapes depending on their power rating and
use. The resistive element material may also vary: metallic wire, carbon, etc. The resistor most
commonly used in the laboratory is made of carbon.
Some resistors may have their nominal value stamped on the body of the resistor. More often, however,
the following color code is used to indicate the value:
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ECE 211 Electrical Circuits Lab I
LAB #1
Fall 2013
HOW TO READ THE CODE

First find the tolerance band, it will typically be gold ( 5%) and
sometimes silver (10%).

Starting from the other end, identify the first band - write down the
number associated with that color; in this case Blue is 6.

Now 'read' the next color. Here it is red so write down a '2' next to the
six. (you should have '62' so far.)

Now read the third or 'multiplier exponent' band and write down that
as the number of zeros.

In this example it is two so we get '6200' or '6,200'. If the 'multiplier
exponent' band is Black (for zero) don't write any zeros down.

If the 'multiplier exponent' band is Gold move the decimal point one to
the left. If the 'multiplier exponent' band is Silver move the decimal
point two places to the left. If the resistor has one more band past the
tolerance band it is a quality band.
TOLERANCE
The range of tolerance for a resistor is the actual range of resistance that the resistor should be within
as indicated by the percentage tolerance. To determine if a resistor is within tolerance, the range of
tolerance must be calculated and the resistor must be measured with an ohmmeter.
Example: Determine the range of tolerance for the following resistor
15 ohms
10%
Solution:
10% of 15
is 1.5
By adding and subtracting 1.5 , the range of tolerance is 13.5
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to 16.5
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ECE 211 Electrical Circuits Lab I
LAB #1
Fall 2013
MEASURING RESISTANCE WITH OHMMETER
1.
2.
3.
4.
Isolate the resistance.
Select the ohm function.
Connect the test leads across the component.
If the ohmmeter is not auto-ranging, start on the highest rank and switch down to lower
ranges until an in-range reading is obtained.
5. Do not leave your fingers on the resistor lead while you are making measurements.
Doing so will cause readings of high value resistors to be lower than they really are.
QUESTIONS:
1. Pick three different resistances. Calculate the value and the range of tolerance. Measure the
value. Is it in the range of tolerance?
Color Bands
Value
%TOL
Range of tol
Measured Value
1
2
3
2. What is the value of a resistor having the following color bands and range of tolerance?
a. Red Red Red Silver
b. Green Blue Brown Gold
3. What will happen if you leave your fingers on the leads of a resistor while making a resistance
measurement? Is it a higher or lower value? Why?
4. The following resistor was measured to be 440 : Yellow, Violet, Brown, Gold. Is the resistor in
within tolerance or out of tolerance?
5. Connect a resistance with a voltage source. Change the value of the voltage source and measure
the current for different points. Plot the result setting the y axis as V and the x axis as I. Estimate
the value of the resistance from the slope of the IV curve. Are all the points aligned linearly?
Why?
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