Learning Outcome 1
Select Measuring Instruments
PERFORMANCE STANDARDS
Object or component to be measured is identified.
Correct specifications are obtained from relevant source.
Appropriate measuring instrument is selected in line with job requirement.
What Do You Already Know?
Let us determine how much you already know about selecting measuring instrument. Take this test.
What Do You Need To Know?
Read Information Sheet 1.1 very well then find out how much you can remember and how much you learned by doing Self-check.
Information Sheet 1.1
Electronics is a branch of technology that deals with many applications. Audio electronics, video electronics, digital, medical up to weapons and banking are covered by the influence of electronics. There are quite a number of components used in the application of electronics. To name a few of these electronic components are resistors, capacitors, inductors and semi-conductors.
The most commonly used electronic components in the field are known as resistors. Resistor is a discrete component that offers opposition to the flow of current. Resistors have different types in accordance with the material used like carbon-composition and the wirewound resistor. According to construction, we have the fixed resistor and the variable resistor.
Resistors are very common and are the cheapest electronic components in the market for so many years. Their features are so interesting and are very colorful. That’s why resistors are very popular among students studying electronics.
One distinct feature of this resistance - giving component is the way its value is determined. It uses a set of colors which follows a code for its assumed resistance expressed in OHMS.
Resistors are used in circuits to accomplish two functions, namely:
to limit the magnitude of current through it to certain values.
to place certain magnitudes of voltage across points in a circuit.
• Resistors are either fixed or variable.
• The tolerance of a resistor is the amount that its resistance can vary and still be acceptable.
•The most common types of resistors include carbon-composition, carbon film, metal-film, wire-wound, and surface-mount or chip resistors. Carbon-film and metal-film resistors are better than carbon-composition resistors because they have tighter tolerances, are less affected by temperature and aging, and generate less noise internally.
• Resistors are either carbon composition, wirewound, or film.
• Carbon composition resistors are the most commonly used resistors.
The physical size of a resistor determines its wattage rating: the larger the physical size, the larger the wattage rating. There is no correlation between a resistor’s physical size and its resistance value.
All resistors have a maximum power rating and if exceeded will result in the resistor overheating and becoming damaged.
Standard resistor power rating sizes are 1/8 W, 1/4 W, 1/2 W, 1 W, and 2 W.
Low ohmic value power resistors are generally used for current sensing or power supply applications.
The most common trouble in resistors is an open. An ohmmeter across the leads of an open resistor will read infinite, assuming there is no other parallel path across the resistor.
Resistors are usually color-coded to indicate their resistance value in ohms. Either a four-band or a five band code is used. The five-band code is used for more precise R values. Chip resistors use a three- or four-digit code to indicate their resistance value.
Resistor values may be identified by colored bands:
—The first band represents the first digit.
—The second band represents the second digit.
—The third band represents the number of zeros to be added to the first two digits.
—The fourth band represents the tolerance.
—A fifth band may be added to represent reliability.
Resistor values of less than 100 ohms are shown by a black third band.
Resistor values of less than 10 ohms are shown by a gold third band.
Resistor values of less than 1 ohm are shown by a silver third band.
Resistor values for 1% tolerance resistors are shown with the fourth band as the multiplier.
Resistor values may also be identified by an alphanumerical system.
The BS1852 Standard uses letters and is used to identify large size resistors.
Tolerance is the percentage measure of the accuracy of a resistor from its preferred value with the E6 (20%), E12 (10%), E24 (5%) and E96 (1%) series of tolerance values available.
Show that you learned something by doing this activity
Operation Sheet 1.1
Materials:
20 pieces - Carbon resistors, 1 watt, assorted values
1 pc - Resistor Tabulation form
Procedure:
Screenshot 20 pieces of 4 band resistors from this site https://manuel-io.github.io/data/resistor/
Rename each screenshot resistor to R1, R2, R3....R20
2. Identify the colors of the resistors one by one and record them in the resistor tabulation form.
3. Compute for the resistance value of each resistor by following the color coding scheme.
4. Write the value of the resistance in the tabulation form.
5. Arrange the resistors in such a way that the value is in ascending manner.
Resistor Tabulation Form
How Well Did You Perform?
Find out by accomplishing the Scoring Rubric honestly and sincerely. Remember it is your learning at stake!
Find out by accomplishing the Scoring Rubrics honestly and
sincerely. Remember it is your learning at stake
With perfect score of 10 = 5
With 1 mistake =. 4
With 2 – 3 mistakes = 3
With 4 – 5 mistakes = 2
With more than 5 mistakes =1
Performance Test.
