Scale Reading: Interpreting Measuring Instruments

Content Standards and Performance Standards

Content Standards

The learners demonstrate an understanding of the concepts and principles in performing mensuration and calculations.

Performance Standards

The learners perform mensuration and calculations following safety precautions

Learning Competencies and Objectives

Learning Competency: Interpret the readings in different measuring instruments.

Volt-Ohm-Milliammeter

Used to measure voltage, resistance, and current in electrical circuits. Students will learn to identify its parts and interpret its readings.

Tachometer

Used to measure rotation speed in mechanical systems. Students will understand its functions and learn to read measurements accurately.

Oscilloscope

Used to visualize and analyze signal voltages. Students will identify its components and interpret waveform readings.

Ampere Meter

Used to measure electrical current. Students will learn its applications and how to interpret current readings.

At the end of the lesson, students are expected to explain the function and uses of these instruments, identify their parts, and accurately interpret their readings.

Activating Prior Knowledge

Pass while singing

The cabbage will be passed from student to student as the class sings any type of song.

Answer questions

When the music stops, whoever has the cabbage will peel one page and answer the question written on the cabbage paper.

Lesson Purpose and Connection

1

Personal Connection

Ask students if they have seen their grandfather, father, uncle, or elder brother using Multi tester at home. Let them share their experiences and encounters seeing multi tester being used.

Unlocking Content Vocabulary

Volt-Ohm-Milliammeter (VOM)

It is an instrument that can be is used to measure voltage, current and resistance.

Voltmeter

Measures electrical pressure (voltage) between two points.

Ohmmeter

Measures resistance to electrical flow (resistance).

Milliammeter

Measures small electrical currents (milliamps).

Scale

Refers to the series of graduated marks or numerical settings used to interpret the readings of voltage, current, resistance, and other electrical properties.

Introduction to Volt-Ohm-Milliammeter

1

Voltage, current and resistance in electrical circuit need to be determined and measured. The volt-ohm-milli-ammeter (VOM) is also called as Multimeter.

2

This type of meter performs several functions. In other words, in VOM the several measuring functions are combined in a single unit.

3

It is used to measure voltage, current and resistance.

Types of Volt-ohm-milliammeter/Multimeter

Analog Multimeter

Analog multimeters use a microammeter, voltmeter, and ohmmeter with a moving pointer to show or display its readings.

Digital Multimeter

This device displays the measurements on a digital screen, making it easy to read and understand the results accurately.

Parts of Analog Multimeter

An analog multimeter consists of several key components that work together to measure electrical properties:

Pointer

Shows the values read from the scale.

Scale

Shows the value of what is being measured.

Zero Position Adjuster

Adjusts/positions the needle at the right scale.

Range Selection Knob

Allows switching the function and scale.

Test Pins

They serve as the conductor from the item being tested to the multimeter.

Test Probes

It is used to connect to the device under test.

Zero Ohm Adjustment Knob

Is used to calibrate the multi tester when you want to measure the resistance of an object.

Parts of Digital Multimeter

1

Selector knob

It comes with an arrow pointer to its end to choose the parameter being measured.

2

Display panel

It displays a liquid crystal display, which can show up to four digits under normal conditions and has the provision to show negative sign.

3

Ports

Displays the three main ports on the front of panel.

4

Probes

It is used to establish an electrical connection between the device under test (DUT) and the multimeter.

How to Read Analog Multimeter Results - Step 1

Find the right scale on an analog multimeter

Analog multimeters have needle behind a glass cover, which moves to show the result. Naturally, there are three arcs printed behind the needle. These are three different scales, each of which is used for a different purpose.

Make a voltage scale reading based on your range

Look carefully at the voltage scales, either DC or AC. There should be several rows of numbers beneath the scale. Check which ranges you have selected on the dial and look for a corresponding label next to one of these rows.

How to Read Analog Multimeter Results - Step 2

Estimate the value between numbers

Voltage scales on an analog multimeter work just like an ordinary ruler. The resistance scale, however, is logarithmic, meaning that the same distance represents a different change in value depending on where you are on the scale.

Multiply the resistance reading on an analog multimeter

Look at the range setting that the dial of your multimeter is set to.

Find out more about the dB scale

The "dB" (decibel) scale, typically the lowest, smallest one on an analog meter, requires some additional training to use. It is a logarithmic scale measuring the voltage ratio (also called gain or loss).

Functions of Multimeter

Ohmmeter

Measures resistance in electrical components

DC Voltmeter

Measures direct current voltage

AC Voltmeter

Measures alternating current voltage

DC Milliammeter

Measures small direct currents

Supplementary Learning Resources

The teacher may use instructional videos in utilizing VOM provided he/she mastered the calibration of the instrument. Always refer to the manufacturer's instructional manual when using the VOM or multi-tester, as this is the best guide for using the VOM's features.

Importance of Using Multimeter

1

After watching demonstration videos, ask students to reflect on the importance of using multi meter. Identify at least three importance and what it contributes to ensuring that the devices, appliances, and the like are working in good condition.

2

The teacher should demonstrate in class the proper way of reading multimeters for accurate and realistic application.

Practical Activity: Using VOM for Measurement

Objective

Use the Volt-Ohm-Milliammeter (VOM) to measure voltage, current, and resistance in circuits. Work collaboratively to analyze and measure key electrical parameters. Understand the importance of selecting the correct mode and range when using a VOM.

Materials Needed

Volt-Ohm-Milliammeter (VOM) or Multimeter for each group, Batteries (e.g., AA or 9V), Resistors (e.g., 220Ω, 1kΩ, 10kΩ), Light bulbs or LEDs, Wires for connecting the circuit, Breadboards (optional), Paper and pen for recording results

Group Formation

Divide into groups of 3-4 students. Assign each group a VOM and a small circuit kit (including resistors, battery, light bulb/LED, and wires).

Activity Task: Measuring Voltage

Set the VOM to measure DC voltage (V)

Turn the selector knob to the appropriate DC voltage setting.

Connect the VOM leads across the battery terminals

Connect positive lead to the positive terminal, negative lead to the negative terminal.

Record the voltage

Read and record the voltage measured by the VOM.

Activity Task: Measuring Current

Set the VOM to measure DC current

Turn the selector knob to the appropriate mA or A setting.

Insert the VOM in series with the circuit

Break the circuit at any point and insert the VOM in series with the circuit.

Record the current

Read and record the current flowing through the circuit (measured in milliamps or amps).

Activity Task: Measuring Resistance

Set the VOM to measure resistance

Turn the selector knob to the appropriate Ω setting.

Ensure no power is applied

Disconnect the circuit or ensure there is no power applied.

Measure the resistor

Measure the resistance of the resistor (220Ω, 1kΩ, or 10kΩ) by placing the leads across the resistor.

Record the resistance

Read and record the resistance on your sheet.

Collaborative Analysis

Compare Voltage Readings

Compare the actual voltage of the battery with the VOM reading.

Analyze Current Changes

Discuss how the current measurement changes based on the components in the circuit.

Apply Ohm's Law

Analyze how the resistor value affects the resistance measurement and use Ohm's Law (V = IR) to predict the current for the given resistance.

Group Discussion Questions

Analyzing Measurements

What were the voltage, current, and resistance measurements for their circuit?

Overcoming Challenges

Did they encounter any difficulties in using the VOM? If so, how did they overcome them?

Practical Applications

How does the VOM help in troubleshooting circuits and analyzing electrical components?

Battery Voltage Observations

What did you notice when you measured the voltage of the battery using the VOM?

Current Measurement Insights

How did the current measurement change when you connected the VOM in series with the circuit?

Resistance Findings

What did you learn about the resistance measurement of the resistor in your circuit?

Range Selection Importance

Why is it important to select the correct range on the VOM when measuring voltage, current, or resistance?

Wrap-up and Reflection

Safety and Accuracy

Ask each group to reflect on the importance of using the VOM properly to ensure safety and accuracy in their measurements.

Real-world Applications

Discuss how this activity might apply to real-world scenarios (e.g., fixing electronics, creating circuits, etc.).

Personal Synthesis

In a one sheet of paper write something you understand about the lesson we discussed today.

Evaluation: Multiple Choice Questions

Question 1

What is the primary function of a Volt-Ohm-Milliammeter (VOM)?

To measure temperature

To measure electrical resistance only

To measure voltage, current, and resistance

To generate electrical power

Question 2

In which mode should the VOM be set to measure the resistance of a resistor?

Voltage mode

Current mode

Resistance mode

Frequency mode

Evaluation: Multiple Choice Questions (Continued)

Question 3

What should be the correct procedure when using the VOM to measure current in a circuit?

Insert the VOM leads in parallel with the load

Set the VOM to voltage mode

Set the VOM to current mode and connect it in series with the load

Only measure current when the circuit is powered off

Question 4

What is the unit of measurement when using the VOM to measure resistance?

Amps (A)

Volts (V)

Ohms (Ω)

Milliamps (mA)

Evaluation: Multiple Choice Questions (Final)

Question 5

Which of the following is true when using the VOM to measure voltage?

The circuit must be disconnected

The VOM must be placed in series with the circuit

The VOM must be placed across the component to measure the voltage drop

The VOM must only be used for AC voltage

Evaluation: Multiple Choice Questions (Final)

Answer Key

1. C

2. C

3. C

4. C

Learning Resources: Video References

1

Analog multi meter parts and functions (Part 1)

YouTube. https://youtu.be/6UhX893En6A?si=vsmfbMV2TCQFeFBL

2

Analog multimeter AC & DC voltage reading Part 3

YouTube. https://youtu.be/j9jxh8Hjm-8?si=HLCLHrjaIyK5pN2Z

3

Analog multimeter DC current reading Part4

YouTube. https://youtu.be/YRmeMa5j1qI?si=zfbgd6ngcwwmfXOk

4

Analog multimeter resistance reading Part 2

YouTube. https://youtu.be/rBPw5zC1qCQ?si=s2LT_GVMFkuhXqJO

Learning Resources: Additional References

1

Computer Lesson 101 - Tagalog

How to Measure Current (Amperes) using Analog Multi-meter [Video]. YouTube. https://www.youtube.com/watch?v=CcfQFqcMa7U

2

Fluke

What is a digital multimeter? https://www.fluke.com/enin/learn/blog/electrical/what-is-a-digital-multimeter#

3

James Gatlin

How to use a multimeter like a Pro, the ultimate guide [Video]. YouTube. https://www.youtube.com/watch?v=0loXukB302Q

4

Joy, A. T.

How to use a multimeter, types, components and more. Tameson.com. https://tameson.com/pages/multimeter

Learning Resources: Further Reading

1

Kuhlman, J.

How to Read a Multimeter (with Pictures) - wikiHow. wikiHow. https://www.wikihow.com/Read-a-Multimeter

2

Source of Skills

How to use analog multimeter | Analog multimeter tutorial | Check AC volt with analog multimeter [Video]. YouTube. https://www.youtube.com/watch?v=z8U9ny6ZPKg

3

T, A.

Volt-Ohm-Milli-Ammeter (VOM). Circuit Globe. https://circuitglobe.com/volt-ohm-milli-ammeter-vom.html

Thank You!

Practical Application

Continue practicing with measuring instruments to build your skills and confidence.

Diverse Tools

Remember that each measuring instrument has its specific purpose and proper technique.

Ongoing Learning

Keep exploring the resources provided to deepen your understanding of electrical measurements.