Lesson Descriptions

This library consists of five lessons. This library is designed for participants familiar with AC/DC theory, electrical safety, and electrical print reading. A basic understanding of electronic devices and circuits is recommended. The library describes megohmmeters, Wheatstone bridges, and clamp-on ammeters. It gives examples of the use of these instruments, identifies their components, and defines their functions. The lessons also describe safety and selection considerations for their use, how to set up the instruments, how to connect them to the systems under test, and how to take and read measurements.

Introduction to Megohmmeters


Using the Megohmmeter


Wheatstone Bridge


Using a Wheatstone Bridge


Clamp-on Ammeters

1. Megger Basics
2. Insulation
3. Basic Components
4. Digital Megger
5. Function of a Megger

• Explain the formula for Ohm’s Law.
• Explain how a working knowledge of Ohm’s Law can be helpful when analyzing test results.
• Describe, and give an example of, the use of a megger.
• List the causes of damaged insulation.
• Describe the causes and effects of low resistance readings.
• Identify the basic components of a typical megger.
• Identify the switches on a digital megger.
• Define the function of a megger.

1. Selecting a Megger
2. Setting Up a Megger
3. Attaching Leads to the System
4. Taking a Reading

• Describe safety considerations when using a megohmmeter.
• List considerations when selecting a megger.
• Describe the procedures for setting up a megger.
• Describe how to attach the leads to the system.
• Describe how to take a reading with a megger.

1. What is a Wheatstone Bridge
2. Wheatstone Bridge Components
3. How a Wheatstone Bridge Works

• Define a bridge circuit.
• Identify the components of a Wheatstone bridge.
• Define the function of a Wheatstone bridge.

1. Balancing the Bridge
2. Setting Mechanical Zero
3. Measuring Resistance
4. Interpreting Readings

• Describe how to balance a Wheatstone bridge.
• Describe how to set mechanical and electrical zero on a Wheatstone bridge.
• Describe how to take a reading with a Wheatstone bridge.
• Describe how to interpret a Wheatstone bridge reading.
• Interpret a Wheatstone bridge reading.

1. Components
2. Types of Clamp-on Ammeters
3. Pointer Lock and Peak Value
4. Clamp-on Ammeter Range
5. Clamp-on Ammeter Function
6. Safety and Selection
7. Taking a Reading

• Identify the components of a clamp-on ammeter.
• Describe the range function of a clamp-on ammeter.
• Define the function of a clamp-on ammeter.
• Describe safety and selection considerations for using a clamp-on ammeter.
• Define the “record and lock” features.
• Describe the procedures for setting up a clamp-on ammeter.
• Describe how to take a reading and modify the range of a clamp-on ammeter.