23 Outcome 3: Measuring and Testing Instruments
Section Information
Outcome/Competency: You will be able to use measuring and testing instruments.
Timing: 1h15m
Rationale:
Why is it important for you to learn this skill?
Measurement and testing equipment are an integral part of the powerline technician’s toolkit. These instruments are used to take accurate measurements, test for voltage or current, measure resistance, and perform many other functions. Without these instruments, the technician has no way of knowing if they are working in a safe environment or if proper voltage is being supplied to the customer.
Objectives:
To be competent in this area, the individual must be able to:
- Identify and describe the basic operating principles of electrical measuring devices
- Identify series and parallel connections
Learning Goals
- Distinguish between series and parallel connections
- Describe the application of different testing instruments
Introduction:
In this section you will learn about series and parallel connections, as well as how to use measuring devices such as ammeters, voltmeters, ohmmeters, and wattmeters. You will be presented with concepts and then given opportunities to see or test these devices. You will then test your understanding with some short review exercises.
Instructions:
This outcome is covered in the trade science course. As such, this objective can be used as a review, or omitted if time is short.
- Cover the following content in each topic as a group (either reading out loud or independently) then give an opportunity to answer any questions.
- As you discuss each tool, give students an opportunity to hold the tool. Where possible, demonstrate how the tool is used. Ensure all proper PPE is used and safety should always come first.
- Have students do the review questions independently, then take up answers.
Topic: Series and Parallel Connections (5m)
To use electrical meters properly and safely, we must know the difference between series and parallel connections.
A series connection is a connection that has only one path for current to flow. So, a meter hooked in series must therefore be hooked “directly in line.”
A parallel connection is a connection that creates an alternate path for current to flow. This is basically a series connection with a jumper around it. A jumper or alternate path will always prevent a series connection.
As you will see, it is very important to know which meters are hooked in series and which are connected in parallel.
Topic: Electric Measuring Devices (40m)
Ammeter
An ammeter measures current in amperes (A) and must be hooked in series.
As you can see, the flow of electricity has no choice but to flow through the ammeter. Because of this, an ammeter must have very low resistance (0.01 ohms is typical.) A high resistance would affect the amperage of the circuit.
For example:
As you can see, there is very little effect on the circuit. You can also see that a high resistance would affect the circuit