Basic Electrical Measurements 1. Basic electrical measurements 2 Basic Electrical Measurements Skill...

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Basic Electrical Measurements 1

Transcript of Basic Electrical Measurements 1. Basic electrical measurements 2 Basic Electrical Measurements Skill...

Page 1: Basic Electrical Measurements 1. Basic electrical measurements 2 Basic Electrical Measurements Skill 2 Unit 2: Digital Multimeters.

Basic Electrical Measurements 1

Page 2: Basic Electrical Measurements 1. Basic electrical measurements 2 Basic Electrical Measurements Skill 2 Unit 2: Digital Multimeters.

Basic electrical measurements 2

Basic Electrical Measurements

Skill 2 Unit 2:

Digital Multimeters

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Goals of this presentation:

• Understand how to safely operate a digital multimeter (DMM).

• Learn how to set a DMM to the correct function, for a given measurement.

• Understand how to use a DMM to perform basic measurements.

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A first look at the Digital Multimeter

• Display

• Function Dial

• Probe Input Jacks

• Function Buttons

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• Battery access

• Fuse ratings: 11 amp

On the back...

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Display

It’s important to understand the many different symbols.

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Display

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Function Dial

• OFF

• AC Volts & Hertz V • DC Volts V• Continuity (tone)

• Ohms

• Diodes

• Capacitance• AC Amps A• DC Amps A

))))Ω

Display backlight On/Off

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Probe Jacks

• Common (black)

• Volts, Ohms, etc.

( V Ω )

• Amps

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• Physical Condition

• Leads & Probes

• User Protection

Safety

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Safety Inspection

Physical damage:

• Case

• Display

• Function Buttons

• Selector Dial

• Probe Jacks

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Safety Inspection

Test leads and probes

Safe to 1000 volts (max).

Check test lead resistance: Step 1: Insert leads in V/ and COM

inputs

Step 2: Select , touch probe tipsGood leads are 0.1 - 0.5

How do you check a single test lead?

Visually check for:• Shrouded connectors not damaged: no

insulation pulled away from end connectors.

• Insulation not melted, cut, cracked, etc.

• Probes: Finger guards intact, tips: not loose, broken off or burned.

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Safety Inspection

Checking meter fuses on most meters: Step 1: Plug test lead in V / input.

Step 2: Select

Step 3: Insert probe tip into A input and read value.

(should be less than 0.5 )

Is the fuse okay?

What would an open fuse read?

Note: This test will only confirm that a fuse is good. It will not test for a wrong sized fuse being installed.

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Safety Features

• Auto Ranging

• Reversed Polarity Protection

• 1000 volts protection on leads(higher than maximum range of AC or DC volts)

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DMM Measurements

• Volts (AC & DC)

• Resistance (Ohms Ω)

• Diodes

• Continuity

• Amps (AC & DC)

• Frequency (Hertz)

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DMM Measurements

AC Volts

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DMM Measurements

DC Volts V

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DMM Measurements

Continuity• Tone can be heard when

resistance is typically less than 50 Ω (250 Ω max).

))))

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DMM Measurements

Resistance Ω• Maximum 40 M Ω• Six ranges (auto or manual)

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DMM Measurements

AC Amps A• 10 Amps maximum

• Protected by internal fuse

• Change positive lead to “A” input

• “LEAd” is displayed whenever switching to or from amps mode, as a reminder to change the positive lead.

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DMM Measurements

DC Amps A• 10 Amps maximum

• Protected by internal fuse

• Change positive lead to “A” input

• “LEAd” is displayed whenever switching to or from amps mode, as a reminder to change the positive lead.

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Common DMM / User Hazards

• Voltage contact while in continuity or resistanceProtection: Overload protection in ohms up to the meter’s volt rating.

• Measuring voltage with test leads in current jacksProtection: High energy fuses rated to the meter’s voltage rating.

• Shock from accidental contact with live componentsProtection: Test Leads double insulated, recessed / shrouded,

finger guards. Replace when damaged.

• Using meter or tester above rated voltageProtection: Good karma !

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Summary

What we learned:

• Functions of the DMM

• Safety inspection

• How to check for good test leads

• How to test for open fuses

• Function of overload protection

• Why amperage inputs need fuses

• How to take measurements

• Common user hazards

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Ohm’s Law

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OHM’S LAW

POWER

I

II

I

I

I

I

R

RR R

R

R

RE

E

E

E

EE

E

PP

PP

P

P

P

VOLTS OHMS

AMPS

2

2

2

2

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OHM’S LAW

REP

IE I

Primary Use: DC CircuitsPrimary Use: AC Circuits

- KEEPING IT SIMPLE -

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Review

• Safety check the meter and leads prior to use

• Place the Test Leads in correct input

• Amps input is low impedance 10 A max • Safety- fused use correct fuse only

• Select the correct function for the reading you want

• Min / Max and Hold functions can be useful

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END

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