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BASIC ELECTRONICS
Experiment #1: Introduction to Electrical Measurements - Resistance
Prelab:
Read the manual of your multitester on how to use the ohmmeter.
Objective:
- To introduce the students to some of the frequently used instruments and equipment like the ohmmeter.
- To compare the computed value of the resistor using color coding to the measured value using the ohmmeter.
Materials:
Analog multitester, 10 pcs. 4-band resistors (330Ω, 470Ω, 1kΩ, 1.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩkΩ 3.3kΩ, 4.7kΩ, 5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ.6kΩ, 10kΩ, 100kΩ, 1MΩkΩ, 10kΩ, 100kΩ, 1MΩΩ), breadboard (optional)
Discussion:
Resistors resist the flow of electrical current. Each one has a value that tells how strongly it resists current flow. This value's unit is the ohm, often noted with the Greek letter omega: Ω. The colored bands on a resistor can tell you everything you need to know about its value and tolerance, as long as you understand how to read them. The order in which the colors are arranged is very important, and each value of resistor has its own unique combination.
Here is an example that shows how the table and resistor shown above can be used to figure out a resistor value by proving that yellow-violet-brown is really 470 Ω (read as 470 Ohms): The first stripe is yellow, which means the leftmost digit is a 4. The second stripe is violet, which means the next digit is a 7. The third stripe is brown. Since brown is 1, it means add one zero to the right of the first two digits. The fourth stripe is gold, which means it has a ± 5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ%. Yellow-Violet-Brown = 4-7-0 = 470 Ω. Although the first two bands are fairly straightforward, the third and fourth bands might require a bit more explanation. Multiplier Band Resistor values can get to be very high in number, and there often isn't enough space to use a band for every digit. To get around this, the third band indicates that a certain number of zeros should be added after the first two digits to make up the full resistor value. In the example above, the third stripe is brown, indicating that a single zero should be added to the right of the first two digits. Another example an orange third band with a digit value of 3 would indicate that three zeros should be added to the right of the first two digits. Example: Brown-black-orange resistor. Brown = 1, black = 0, orange multiplier = 10^3 = 000 (3 zeros) 1-0-000 = 10000Ω or 10kΩ Tolerance Band The fourth color band indicates the resistor's tolerance. Tolerance is the percentage of error in the resistor's resistance, or how much more or less you can expect a resistor's actual measured resistance to be from its stated resistance. A gold tolerance band is 5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ% tolerance, silver is 10%, and no band at all would mean a 20% tolerance. For example: A 470 Ω resistor has a gold tolerance band. Tolerance = value of resistor x value of tolerance band = 470 Ω x 5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ% = 470 Ω x 0.05kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ = 23.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ Ω 470 Ω stated resistance +/- 23.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ Ω tolerance means that the resistor could range in actual value from as much as: 470 Ω + 23.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ Ω = 493.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ Ω 470 Ω – 23.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ Ω = 446kΩ, 10kΩ, 100kΩ, 1MΩ.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ Ω So the range of the resistor value is 446kΩ, 10kΩ, 100kΩ, 1MΩ.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩΩ to 493.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩΩ. Some projects require your measurements to be more precise than others, and for this reason the tolerance band is useful in identifying which resistor will give you a more accurate resistance reading. The smaller the tolerance percentage is, the higher the precision in your measurements.
BASIC ELECTRONICS
Experiment #1: Introduction to Electrical Measurements - Resistance
EVALUATION SHEET:
Name: ______________________________________________________
Date: ________________________
Table 1:
Resistor
Values
Color Bands Range
Values
Measured
Value
% Error
1 st^ color 2 nd^ color 3 rd^ color 4 th^ color
1kΩ = 1000 Ω 1.5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩkΩ = 15kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ00 Ω 3.3kΩ = 3300 Ω 4.7kΩ = 4700 Ω 5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ.6kΩ, 10kΩ, 100kΩ, 1MΩkΩ = 5kΩ 3.3kΩ, 4.7kΩ, 5.6kΩ, 10kΩ, 100kΩ, 1MΩ6kΩ, 10kΩ, 100kΩ, 1MΩ00 Ω 10kΩ = 10000 Ω 100kΩ = 100000 Ω 1MΩΩ = 1000000 Ω
Computation for Range: (use additional sheet if necessary)
Computation for Percentage Error: (use additional sheet if necessary)
