Ammeters, Meggers, and Wheatstone Bridge

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


Description: This is the first lesson in the iKNOW™ Ammeters, Meggers, and Wheatstone Bridge Library. This lesson explains Ohm’s Law and how it is used when analyzing test results. The basic components, uses, and functions of a megohmmeter are described. Insulation and causes of insulation damage are also covered.

Prerequisites: None

Topics:

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

Objectives:

  • 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

Using the Megohmmeter


Description: This is the second lesson in the iKNOW™ Ammeters, Meggers, and Wheatstone Bridge Library. This lesson describes safety issues to consider when using a megohmmeter, how to select the correct megger for the job, setup, and the steps necessary to take a megger reading.

Prerequisites: Review of the lesson, Introduction to Megohmmeters is recommended

Topics:

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

Objectives:

  • 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

Wheatstone Bridge


Description: This is the third lesson in the iKNOW™ Ammeters, Meggers, and Wheatstone Bridge Library. This lesson explains what a bridge circuit is, the purpose and components of a Wheatstone bridge, and its function.

Prerequisites: None

Topics:

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

Objectives:

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

Using a Wheatstone Bridge


Description: This is the fourth lesson in the iKNOW™ Ammeters, Meggers, and Wheatstone Bridge Library. This lesson explains how to balance a Wheatstone bridge and the process used to set mechanical and electrical zero. How to interpret the readings of a Wheatstone bridge is also explained.

Prerequisites: Review of the lesson, Wheatstone Bridge, is required.

Topics:

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

Objectives:

  • 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

Clamp-on Ammeters


Description: This is the final lesson in the iKNOW™ Ammeters, Meggers, and Wheatstone Bridge Library. This lesson presents the components and features and functions of clamp-on ammeters. The lesson also describes safety considerations that should be noted when selecting a clamp-on ammeter. Instruction in the procedures for setting up, taking readings, and modifying the range of a clamp-on ammeter are also covered.

Prerequisites: None

Topics:

  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

Objectives:

  • 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