ECE lab1 - Resistor and Color code lab PDF

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Resistor and Color code lab...

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Temple University

College of Engineering

Department of Mechanical Engineering

Lab Report Cover Page ECE 2113

Experiment # 1: Resistors and Color Code

Nelson Chan Alan Henry

September 17, 2018 I.

Introduction

Many electrical circuits contain multiple variations of resistor networks. Resistors play a vital role in the distribution and limiting of electric current in a circuit. Learning to identify and measure the values of these components to effectively design and troubleshoot electrical and electronic circuits is vital when building a circuit. Each resistor has three to five colored bands on them that represent different values. Reading and decoding these bands allows you to determine a resistor’s value and accuracy. In Figure 1.1, the chart shows the three and four band resistor color codes. Five percent tolerance resistors use the three band code on the top of the diagram. Figure 1.1

In this system of notation colors being painted on the body of the resistors corresponds to some predefined numerical values. In general dark colors like black and brown correspond to lowest numbers, 0 and 1 respectively and the light colors indicate higher numerical values. The first two or three bands determine the significant digits based on the resistor accuracy. High accuracy resistors use three bands while standard accuracy resistors use two bands. The next band is the multiplier of the significant digits. The last band is the tolerance. The tolerance is a percentage that determines the expected range of resistance values based on the marked value. The following equation shows how to compute the range of expected resistance values for a known marked value: Rmax =R ( 1+[Tolerance ] )

Equation 1.1

Rmin =R(1− [Tolerance ] )

Equation

where Rmax ∧ Rmin is the maximum and minimum resistance, respectively, and R is the marked value on the resistor. Another way to identify the value of a resistor is to use a Digital MultiMeter to measure its resistance. The Digital Multi-Meter passes a known amount of current to through its leads. The meter then measures the voltage drop across the resistor being tested and calculates the resistance using Ohm’s Law. The purpose of this lab is to: 1. To identify resistor values and tolerances from the color code and measurement. 2.

To

learn

to

use

the

ohmmeter

to

measure

resistance

and

continuity.

3. To compare the color coded resistor tolerance with the actual measured resistance value. II.

Procedure

In this experiment, a set of resistor were provided in which the resistance must be determined by using a color code chart, Figure 1.1, and recorded to Table 2.1. Using Figure 1.1, determine its coded resistance, in units of ohms (Ω), and tolerance, in percentage. Repeat this step until the set of resistors in Table 2.1 is complete. After the coded color and tolerance is determine, calculate and record the maximum and minimum resistance to Table 2.2 using Equation 1.1 and 1.2, with the coded resistance and tolerance in Table 2.1. Using the Digital Multi-Meter, set to the Ohms function, measure the resistance of the resistor and record the measured resistance (using proper Ω, kΩ or MΩ notation) in Table 2.3. By comparing the measured resistance with the maximum and minimum coded resistances, decide if the resistor is within tolerance. Record the result (YES or NO) and determine the percent difference. III.

Results and Discussion

Resistors of various values were found and the corresponding band colors and band numerical values were recorded in Table 2.1. The 22Ω resistor served as an example.

Table 2.1: Resistor Band Colors and Values

Using the Rmax ∧ Rmin equations from above, the maximum and minimum resistance for each resistor was determined. The resistances are recorded in Table 2.2 Table 2.2: Maximum and Minimum Resistances

The Digital Multi-Meter was used to read the actual resistance level of each resistor and the percent difference was determined to see if the reading fell within the tolerances. The measured values and percent differences are recorded in Table 2.3 with the 22Ω resistor as an example.

Table 2.3: Measured values vs. labeled values

The table shows that all of the actual values for the resistors fell within their tolerances. For Exercise 1, the ohmic values and tolerances for the band colors in the following table were determined using the chart in Figure 1.1. Exercise 1 Table: Ohmic values and tolerances

To review, to measure the resistance of a resistor, wires attached to a Digital Multi-Meter are connected to each end of the resistor. Software on a computer reads the resulting value.

IV.

Conclusion

During this lab, the resistance values of resistors was determined by matching band colors with their numerical values based on a chart. The bands also indicated a tolerance value. A Digital Multi-Meter was used to measure the actual resistance of the resistors and the values were compared to their band values. The measured resistances were all well within the tolerance....