Transcript Ch 22 Electrical Tester and DMM

22
Circuit Testers and Digital
Meters
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FUSED JUMPER WIRE
• Purpose and Function
• Fuse
• Alligator clip ends
• Good-quality insulated wire
• Uses of a Fused Jumper Wire
• Supply power or ground
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
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CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.1 A technician-made fused jumper lead, which is equipped with a red 10 ampere fuse. This fused
jumper wire uses terminals for testing circuits at a connector instead of alligator clips.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
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CIRCUIT TESTERS AND DIGITAL METERS
FUSED JUMPER WIRE
• Caution: Never use a fused jumper wire to bypass any
resistance or load in the circuit.
• The increased current flow could damage the wiring
and could blow the fuse on the jumper lead.
• Be very cautious when working on or around any
computer circuit.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
TEST LIGHT
• Non-powered Test Light
• A test light is used to detect battery voltage potential
at various test points
• Uses of a 12-Volt Test Light
• Electrical power
• Grounds
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
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CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.2 A 12-volt test light is attached to a good ground while probing for power.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
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CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.3 A test light can be used to locate an open in a circuit. Note that the test light is grounded at a
different location than the circuit itself.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
DIGITAL METERS
• Terminology
• Measuring Voltage
• DC volts (DCV)
• AC volts (ACV)
• Range
• Measuring Resistance
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.4 Typical digital multimeter. The black meter lead is always placed in the COM terminal. The red meter
test lead should be in the volt–ohm terminal except when measuring current in amperes.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
CHART 22.1 Common symbols and abbreviations used on digital meters.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.5 Typical digital multimeter (DMM) set to read DC volts.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
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CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.6 A typical auto-ranging digital multimeter automatically selects the proper scale to read the voltage
being tested. The scale selected is usually displayed on the meter face. (a) Note that the display indicates “4,”
meaning that this range can read up to 4 volts. (b) The range is now set to the 40 volt scale, meaning that the meter
can read up to 40 volts on the scale. Any reading above this level will cause the meter to reset to a higher scale. If
not set on auto-ranging, the meter display would indicate OL if a reading exceeds the limit of the scale selected.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.7 Using a digital multimeter set to read ohms (Ω) to test this light bulb. The meter reads the resistance
of the filament.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.8 Many digital multimeters can have the display indicate zero to compensate for test lead resistance.
(1) Connect leads in the V Ω and COM meter terminals. (2) Select the Ω scale. (3) Touch the two meter leads
together. (4) Push the “zero” or “relative” button on the meter. (5) The meter display will now indicate zero ohms of
resistance.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
DIGITAL METERS
• Caution: T he circuit must be electrically open with no
voltage present when using an ohmmeter.
• If current is flowing when an ohmmeter is connected,
the reading will be incorrect; meter can be destroyed
• Measuring Amperes
• Tech Tip
• Fuse Your Meter Leads!
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.9 Measuring the current flow required by a horn requires that the ammeter be connected to the circuit
in series and the horn button be depressed by an assistant.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.10 Note the blade-type fuse holder soldered in series with one of the meter leads. A 10 ampere fuse
helps protect the internal meter fuse (if equipped) and the meter itself from damage that may result from excessive
current flow if accidentally used incorrectly.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
DIGITAL METERS
• Caution: A n ammeter must be installed in series with the
circuit to measure the current flow in the circuit.
• If a meter set to read amperes is connected in
parallel, such as across a battery:
• The meter or leads may be destroyed, or fuse will
blow, by the current available across the battery.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
INDUCTIVE AMMETERS
• Operation
• AC/DC Clamp-On Digital Multimeters
• Tech Tip
• Over-Limit Display Does Not Mean the Meter Is
Reading “Nothing”
• Think of Money
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.11 An inductive ammeter clamp is used with all starting and charging testers to measure the current
flow through the battery cables.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.12 A typical mini clamp-on-type digital multimeter. This meter is capable of measuring alternating
current (AC) and direct current (DC) without requiring that the circuit be disconnected to install the meter in series.
The jaws are simply placed over the wire and current flow through the circuit is displayed.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
FIGURE 22.13 Typical digital multimeter showing OL (over limit) on the readout with the ohms (Ω) unit selected.
This usually means that the unit being measured is open (infinity resistance) and has no continuity.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
HOW TO READ DIGITAL METERS
• Steps to Follow
• Select the proper unit of electricity for what is being
measured
• Place the meter leads into the proper input terminals
• Measure the component being tested
• Auto-range
• Interpret the reading
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
CHART 22.2 Sample meter readings using manually set and auto-ranging selection on the digital meter
control.
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
HOW TO READ DIGITAL METERS
• Purchase a Digital Meter That Will Work for Automotive
Use
• Caution: If the meter leads are inserted into ammeter
terminals, even though the selector is set to volts:
• The meter may be damaged or an internal fuse may
blow if the test leads touch both terminals of a battery
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
22
CIRCUIT TESTERS AND DIGITAL METERS
HOW TO READ DIGITAL METERS
• Note: Pay attention to the units displayed on the meter
face and convert to whole units.
• Note: When converting from kilohms to ohms, make the
decimal point a comma
Introduction to Automotive Service
James Halderman Darrell Deeter
© 2013 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458