Lab 4.2.1 Safe Handling and Use of a Multimeter

Estimated time: 15 min.

Objectives:

> - Learn how to use or handle a multimeter correctly.

Background:

> A multimeter is a powerful electrical testing tool that can detect voltage levels, resistance levels and open/closed circuits. It can check both Alternating Current (AC) and Direct Current (DC) voltage. Open and closed circuits are indicated by resistance measurements in Ohms. Each computer and networking device consists of millions of circuits and small electrical components. A multimeter can be used to debug electrical problems within a computer/networking device or between networking devices.

Tools / Preparation:

> Prior to starting the lab, the teacher or lab assistant should have several multimeters available (one for each team of two students) and various batteries for testing. Work in teams or two. You should review semester 1 On-line Lesson 4. The following resources will be required:

> - A digital multimeter (Fluke 12B or similar) for each team
> - A manual for the multimeter
> - A battery (i.e. a 9v, 1.5V or lantern, it doesn't matter) for each team to test.

Notes: The multimeter is a sensitive piece of electronic test equipment. Be sure that you do not drop it or throw it around. Be careful not to accidentally nick or cut the red or black wire leads (probes). Since it is possible to check high voltages, extra care should be taken when doing so to avoid electrical shock.

Worksheet

> Perform the following steps to become familiar with the handling of the multimeter.

> 1. Insert the red and black leads (probes) into the proper jacks on the meter. The black probe should go in the COM jack and the red probe should go in the + (plus or positive) jack.
> 2. Turn on the multimeter (click/turn to the on button). What model of multimeter are you working with?
>    What action must you take to turn the meter on?
> 3. Switch or turn to different measurements (i.e. voltage, ohms, etc.). How many different switch positions does the multimeter have?
>    What are they?
> 4. Switch or turn the multimeter to the voltage measurement. What is the symbol for this?
> 5. Put the tip of the red (positive) lead on one end of a battery (+ side), battery and put the tip of the black (negative) lead on the other end of a battery. Is any number showing up on the multimeter?
>    If not, make sure you switch to the correct type of measurement (Vol, voltage, or V). If the voltage is negative, reverse your leads.

Reflection Questions:

> 1. Name one thing that you should not do to a multimeter.
> 2. Name one important function of a multimeter.
> 3. If you get a negative voltage when measuring a battery, why is that?