MAC TOOLS EM721 User Manual

EM721 Digital Multimeter

To reduce the risk of injury, read and
understand these safety warnings and
instructions before using the tool.
Keep these instructions with the tool
for future reference. If you have any
questions, contact your MAC TOOLS
representative or distributor.

WARNING

Automotive Multimeter

User Manual

EM721

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WARRANTY

This instrument is warranted to be free from defects in material and workmanship for a period of one
year. Our obligation to the original purchaser shall be limited to repairing or replacing, at our expense (not
including shipping charges) a defective tool if returned by the original purchaser within one year from the
date of purchase, all incoming shipping charges prepaid. THIS WARRANTY DOES NOT COVER DEFECTS
OR DAMAGES TO THE TOOL (i) after the warranty period expires; (ii) resulting from misuse or abnormal
operation; (iii) resulting from a failure to properly maintain or operate the tool; or (iv) resulting from any repair
or maintenance services performed by any party other than Mac Tools. This warranty does not cover expandable
items such as batteries and/or fuses.

LIMITATION OF LIABILITY

This manual tells you how to use the meter to perform diagnostic tests and to nd possible locations of
automotive electronic problems. It does not tell you how to correct the problems. Once you have located a
problem, consult your car’s service manual or other manuals to provide specic information needed for repair.

All information, illustrations, and specications contained in this manual are based on the latest information
available at the time of publication. The right is reserved to make changes at any time without notice.

TABLE OF CONTENTS

1. Safety Information .............................................................................. 4

2. Introduction ....................................................................................... 7

3. Front panel ........................................................................................ 8

4. Understanding the Display ................................................................ 14

5. Basic Electrical Tests and Measurements ........................................... 17

6. Basic Automotive Measurements ........................................................ 26

7. Basic Automotive Diagnostic Testing .................................................. 33

8. Basic Automotive Component Testing ................................................. 58

9. Summary of Automotive Electrical System Tests .................................. 67

10. Specications .................................................................................. 70

11. General Specications ..................................................................... 75

12. Maintenance .................................................................................... 76

13. Meter-PC Communication Software Instruction .................................... 77

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METER OVERVIEW

Measurement limits:

DC Voltage 0.1mV to 1000V

AC Voltage 0.001V to 750V

RPM IP 30 to 9000 RPM

RPM IG 60 to 12000 RPM

DC Current (Amperes) 0.1µA to 10A

AC Current (Amperes) 0.1µA to 10A

Resistance (Ohms) 0.1 to 40MΩ

Frequency (Hertz) 0.5Hz to 200kHz

% Duty Cycle 0 to 99.9%

Dwell (Degrees) 0° to 356.4°

Pulse Width (Milliseconds) 0.1ms to 1999.9ms

Temperature (Fahrenheit/Celsius) - 40°F to +2498°F (- 40°C to +1370°C)

Capacitance (Microfarads) 0.001µF to 999µF

Continuity Check Beep at < about 40Ω in the 400Ω range

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1. SAFETY INFORMATION

This meter has been designed according to IEC 61010 concerning electronic measuring instruments with a
measurement category (CAT III 1000V) and Pollution Degree 2.

WARNING

TO AVOID POSSIBLE ELECTRIC SHOCK OR PERSONAL INJURY, FOLLOW THESE GUIDELINES:

• Do not use the meter if it is damaged. Before you use the meter, inspect the case.

Pay particular attention to the insulation surrounding the connectors.

• Inspect the test leads for damaged insulation or exposed metal. Check the test leads for continuity.

Replace damaged test leads before you use the meter.

• Do not use the meter if it operates abnormally. Protection may be impaired. When in doubt, have the meter

serviced.

• Do not operate the meter where explosive (or ammable) gas, vapor, or dust is present.

• Do not apply more than the rated voltage, as marked on the meter, between terminals or between any

terminal and earth ground.

• Before use, verify the meter’s operation by measuring a known voltage.

• When servicing the meter, use only specied replacement parts.

• Use caution when working with voltage above 30V ac rms, 42V peak, or 60V dc.

• Such voltages pose a shock hazard.

• When using the probes, keep your ngers behind the nger guards on the probes.

• When making connections, connect the common test lead before you connect the

• live test lead. When you disconnect test leads, disconnect the live test lead rst.

• Remove the test leads from the meter before you open the battery cover or the case.

• Do not operate the meter with the battery cover or portions of the case removed or loosened.

• To avoid false readings, which could lead to possible electric shock or personal injury, replace the battery

as soon as the low battery indicator ( ) appears.

• Do not use the meter in a manner not specied in this manual or the safety features provided by the meter

may be impaired.

• When measuring current using the test leads, turn off circuit power before connecting the meter in the

circuit. Remember to place the meter in series with the circuit.

• To avoid electric shock, do not touch any naked conductor with hand or skin; and do not ground yourself

while using the meter.

• Adhere to local and national safety codes. Individual protective equipment must be used to prevent shock

and arc blast injury where hazardous live conductors are exposed.

• Follow the relevant requirements and safety procedure specied in the users manual and service manual

provided by the manufacturer of the vehicle under test.

• Exhaust gas contains carbon monoxide which is odorless, causes slower reaction time, and can lead to

serious injury. When testing vehicle with the engine running, testing should always be done in a well­ventilated area or vent exhaust gas outside the building.

• Set the parking brake and block the wheels before testing or repairing the vehicle, unless instructed

otherwise. It’s especially important to block the wheels on front-wheel drive vehicles: the parking brake
doesn’t hold the drive wheels. The ignition orfuel system must always be disabled when performing
starting system tests.

• Always wear safety glasses when working near battery.

• Do not smoke or allow open ames or sparks in the work area. Gasoline fumes and gases produced by

battery are highly explosive.
Keep cigarettes, sparks, and open ames away from batteries at all times.

• To avoid personal injury, do not touch any moving or hot object. Keep body and clothing clear of moving or

hot engine parts at all times.

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• Especially in marine applications with inboard or inboard/outboard engines, make sure work area is

well ventilated. Operate bilge blower for at least four minutes before starting engine or making test lead
connections.

• Always avoid working alone.

• Do not use the meter if the meter or your hand is wet.

• Remaining endangerment: When an input terminal is connected to dangerous live potential, it is to be

noted that this potential can occur at all other terminals!

• CAT III - Measurement Category III is for measurements performed in the building installation. Examples

are measurements on distribution boards, circuit breakers, wiring, including cables, bus-bars, junction
boxes, switches, socket-outlets in the xed installation, and equipment for industrial use and some other
equipment, for example, stationary motors with permanent connection to the xed installation. Do not use
the meter for measurements within Measurement Categories IV.

CAUTION

TO AVOID POSSIBLE DAMAGE TO THE METER OR TO THE EQUIPMENT BEING TESTED,

FOLLOW THESE GUIDELINES:

• Disconnect circuit power and discharge all capacitors thoroughly before testing resistance, diode,

capacitor, temperature, and continuity.

• Use the proper terminals, function, and range for your measurements.

• Before measuring current, check the meter’s fuses and turn off power to the circuit before connecting the

meter to the circuit.

• Before turning the rotary switch to change functions, disconnect the test leads from the circuit being tested.

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Symbols

Alternating Current

Direct Current

Both direct and alternating current

Caution, risk of danger, refer to the operating manual before use.

Caution, risk of electric shock.

Earth (ground) Terminal

Fuse

Conforms to European Union directives

The equipment is protected throughout by double insulation or reinforced insulation.

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2. INTRODUCTION

The meter is a handheld, battery-operated automotive multimeter. It is a very useful test tool.

This users manual tells you how to use the meter. You may also need a manual that provides technical
information for the vehicle you plan to test. The most important information resources are the vehicle’s service
repair manuals generally available for purchase through automotive dealers. They are also available through a
number of publishers that specialize in providing technical information manuals to independent repair garages.

This users manual servers as a guide to get you started with troubleshooting. You real learning can best be
accomplished through experience. As you become more procient in using this automotive multimeter for
troubleshooting, you will quickly learn how certain electrical symptoms relate to various driveability problems.

Meter Features

• Accurate frequency and pulse measurements with 20,000 count on the high resolution 4000 count display.

• High-speed 41-segment analog bargraph updates 20 times/sec - For nearly seamless real-time accuracy.

• Accurate automotive electronics test and advanced measurements with DC/AC Volts, DC/AC Amps,

Resistance, etc

• Direct reading of dwell without using duty cycle-to-dwell conversion chart when testing electronic fuel

injection, feedback carburetors, and ignition systems

• RPM measurement for automotive engines with 1 to 12 cylinders using the test leads or the inductive

pickup

• mS-pulse width function to test on-time of fuel injectors of both PFI (Port Fuel Injector) and TBI (Throttle

Body Injector) types

• For accurate measurements of RPM, dwell, duty cycle, and mS-pulse width of injectors, the meter provides

seven-step adjustable +/-triggers on 1 to 12 cylinders, either 2- or 4-cycle for outboards, motorcycles, and
conventional engines

• Temperature measurement up to 2,498°F (1,370°C) for catalytic converters, fan switch, etc.

• Capacitance and non-automotive frequency measurement

• Back-lighted display

• USB communication

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3. FRONT PANEL

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891011

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1. Digital Display

Digital readings are displayed on a 4,000 count display with polarity indication and automatic decimal
point placement. When this meter is turned on, all display segments and symbols appear briey during
aself test.

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2. Analog Bargraph

The bargraph provides an analog representation of readings and updates 20 times per second. The 2×41
segment bargraph illuminates from left to right as the input increases. The bargraph is easier to read when
the data causes the digital display to rapidly change. It is also useful for trend setting or directional data.
The bargraph also indicates the trigger level.

3. “±TRIG “Button

This “±TRIG” button can be used to toggle between negative (-) and positive (+) trigger slope and adjust
trigger level.

When the meter is in RPM, duty cycle, pulse width, frequency (automotive Hz) or dwell measurement
function, hold down the “±TRIG” button for one second to toggle between negative (-) and positive (+)
trigger slope. The slope is indicated by the + or - sign next to “TRIG” in the lower-left corner of the display.
The meter defaults to negative (-) trigger slope. Once the trigger slope is selected, press the “±TRIG” button
repeatedly to adjust trigger level if the meter reading is too high or unstable.

The trigger level adjustment has seven steps. Press the “±TRIG” button to move one step at a time to select
a suitable trigger level.

TRIGGER STEP

Voltage Level

(RPM, Duty Cycle, mS,

Hz (automotive), Dwell)

Approximate Trigger Level

as Indicated by Bargraph

+4 +8.2V

+3 +6.8V

+2 +3.2V

+1 +1.4V

-1 -1.4V

-2 -3.2V

-3 -6.8V

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4. “REL” Button

Used to enter or exit Relative mode as well as to turn on or off the USB communication function.

Press this “REL” button to enter Relative mode. The meter stores the present reading as a reference for
subsequent measurements. “ ” appears as a Relative mode indicator, and the display reads zero.

In Relative mode, when you perform a new measurement, the display shows the difference between the
reference and the new measurement.

To exit the Relative mode, just press the “REL” button again. “ ” disappears.

Note:

•

The meter enters manual range mode when you enter the Relative mode.

• When you use Relative mode, the actual value of the object under test must not exceed the full-

range reading of the selected range. Use a higher measurement range if necessary.

• Relative mode is not available in diode and continuity test functions.

Press and hold down this “REL” button for 1 second to turn on the USB communication function, “ ”
will appear on the display as an indication. To turn off the USB communication function, press and hold
down this “REL” button for 1 second again. “ ” disappears.

5. “DWL” Button

This “DWL” button can be used to select dwell measurement function or switch between resistance and
continuity test functions.

When the meter is in RPM IG function, you can press this “DWL” button to select dwell measurement
mode; “DWL°” will appear on the display as an indication. Dwell is the number of degrees of distributor
rotation where the points remains closed. Dwell can be measured for 1 to 12 cylinders. The conversion
between duty cycle and dwell can be obtained using the following formula:

% Duty Cycle =

Dwell (in degrees) × No. of Cylinders × 100%

360 degrees

Dwell =

360 degrees

×

% Duty Cycle

No. of Cylinders 100%

When the meter is in the dwell function, you can press the “DWL” button again or the “% DUTY” button to
return to the function the meter was in just before entering dwell function.

When the rotary switch is in the “Ω ” position, you can press the “DWL” button to switch between
resistance and continuity test functions. A continuity test can be used to verify that you have a closed
circuit. The continuity function detects opens and shorts lasting as little as 100 milliseconds. In the 400Ω
range, resistance of less than about 40Ω causes the built-in buzzer to sound. This can be a valuable
troubleshooting aid when looking for intermittent faults associated with connections, cables, relays,
switches, etc.

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6. “DC/AC” Button

Used to switch between DC and AC function or between °C and °F.

When the rotary switch is in “ “, “10 “, “m ” or “μ ” position, you can press this “DC/AC” button to
switch between DC and AC function; when AC function is selected, “ ” will appear on the display as an
indication; when DC function is selected, “ ” will appear on the display as an indication.

You can press the “DC/AC” button to switch between °C and °F when the rotary switch is in “TEMP”
position. When Celsius temperature measurement is selected, “°C” will appear on the display as an
indication; and when Fahrenheit temperature measurement is selected,“°F” will appear on the display as
an indication.

7. Rotary Switch

Following functions are selected by setting the rotary switch:

Switch

Position Function

Volts DC/AC

m

Millivolts DC only

Ω

Resistance/Continuity test (Ohms)
Diode test

Capacitance (Microfarads)

TEMP Temperature (Fahrenheit and Celsius)

Frequency (non-automotive frequency) measurement (Hertz)

RPM measurement on 2- or 4-stroke engines using the Inductive Pickup on a
spark plug wire.

RPM measurement on 1 to 12 cylinder engines using the test leads in the
primary side of the ignition coil and Duty Cycle, Pulse Width, Hz (automotive),
and Dwell measurement.

10

Current (Amperes) DC/AC

m

Current (Milliamperes) DC/AC

μ

Current (Microamperes) DC/AC

OFF Turns off the meter

8. “ ” Terminal

Input terminal for voltage, resistance, continuity, RPM, diode, frequency, capacitance, temperature, duty
cycle, pulse width and dwell measurements.

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9. “COM” Terminal

Common (return) terminal for all measurements.

10. “mA μA” Terminal

Input terminal for current measurements < 400mA.

11. “A” Terminal

Input terminal for current measurements between 400mA and 10A.

12. “RANGE” Button

This “RANGE” button can be used to:

• Toggle between autorange mode and manual range mode as well as to select desired manual range.

• Select number of cylinders (1, 2, 3, 4, 5, 6, 8, 10, or 12) to match the engine when the meter is in

RPM IG or dwell function.

• Toggle between 2-Cycle engine (or distributorless ignition system 4-Cycle engine) and 4-Cycle engine

when the meter is in RPM IP function.

In a function which has both autorange mode and manual range mode, the meter defaults autorange mode
and “ ” appears on the display as an indication. You can press the “RANGE” button to enter manual
range mode, “ ” will disappear and the meter will stay in the present range.

In manual range mode, you can press the “RANGE” button to select the next higher range. After the highest
range, the meter wraps to the lowest range. To exit manual range mode and return to autorange mode,
press and hold down the “RANGE” button for 1 second; “ ” will appear on the display as an indication.

Always select a range higher than you expect the current or voltage to be. Then select a lower range if
better accuracy is needed. If the range is too high, the readings are less accurate. If the range is too low,
the meter shows “OFL” as an overload indication.

When the meter is in the RPM IG or dwell function, press the “RANGE” button to toggle between 1, 2, 3, 4,
5, 6, 8, 10, 12 cylinder engines. The selected number of cylinders is indicated by the number preceding
CYL on the display.

When the meter is in the RPM IP function, press the “RANGE” button to toggle between 2-cycle engine
(or distributorless ignition system 4-cycle engine) and 4-cycle engine; the selected number of cycles (or
strokes) is indicated by the corresponding symbol (“ ” or “ ”).

13. “% DUTY” Button

When the meter is in RPM IG function, press this “% DUTY” button to measure duty cycle (or duty factor)
in percent; % readout is displayed. Duty cycle is the percentage of time a signal is above or below a trigger
level during one cycle.

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To select pulse width function, press the “% DUTY” button again; mS readout is displayed. Pulse width is
the length of time an actuator is energized. For example, fuel injectors are activated by an electronic pulse
from the Engine Control Module. This pulse generates a magnetic eld that pulls the injector nozzle valve
open. The pulse ends and the injector nozzle is closed. This Open-to-Closed time is the pulse width and is
measured in milliseconds (mS)

To select the frequency function, press the “% DUTY” button once more; Hz readout is displayed.
Frequency is the number of cycles a signal completes each second.

You can step through RPM, duty cycle, pulse width, and frequency by pressing this “% DUTY” button.

When the rotary switch is in the “RPM IG” position, you can press the “DWL” button to select dwell
measurement function; “DWL°” will appear on the display as an indicatior for the dwell measurement
function.

When in dwell measurement function, you can press the “DWL” button again or the” % DUTY” button to go
back to the previous function from which the meter entered the dwell measurement function.

14. “HOLD” Button

Used to enter or exit Hold mode as well as to turn on or off the backlight.

Press this “HOLD” button to enter the Hold mode. “ ” appears on the display as an indication and the
meter holds the present reading on the display. In the Hold mode, whenever meter detects a new stable
reading, the meter sounds a beep and displays the new stable reading. To exit the Hold mode, press the
“HOLD” button again. “ ” disappears.

Note: When the meter is in the Recording or Relative mode, the Hold function simply freezes the present

reading and will not update the the display with new stable reading.

To turn on or off the backlight, press and hold down this “HOLD” button for 1 second.

15. “REC” Button

Press the “REC” button to enter the Recording mode, “ ” will appear on the display as an indication.
(The meter will exit autorange mode automatically and stay in the present range when it enters Recording
mode.) This function allows you to record maximum, minimum, and average values for a series of
measurements in the same function and range. This meter beeps each time a new maximum or minimum
value is recorded. Press the “REC” button to scroll through the stored maximum, minimum, and average
values. When an overload is captured, a beeper tone is emitted and the meter displays “OFL” as an overload
indication. The meter can only record for 24 hours in this mode.

Note: In diode or continuity function, the Recording mode is not available.

16. USB Port

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Auto Power Off

When the rotary switch is in the position, the meter will turn off automatically if you have not operated the
meter for about 30 minutes (1 hour in the Recording mode) while the input voltage is less than 1V.

When the rotary switch is in other position, the meter will turn off automatically if you have not operated the
meter for about 30 minutes (1 hour in the Recording mode).

About 30 seconds before the meter turns off automatically, the symbol “ ” will start ashing to remind you
that the meter will turn off.

To turn on the meter again, set the rotary switch to OFF position rst and then set it to a desired position.

To disable the automatic power-off feature, turn on the meter while holding down the “HOLD” button.

Using Inductive Pickup

The meter comes with an Inductive Pickup. The Inductive Pickup takes the magnetic eld generated by the
current in the spark plug wire and converts it to a pulse that triggers the meter’s RPM measurement.

4. UNDERSTANDING THE DISPLAY

12567891011121314

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25

26

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1. . Displayed when the RPM IG mode is selected. In this mode, revolutions per minute on 1 to
12cylinder engines can be measured using the test leads on the primary side of the ignition coil.

2. . Displayed when the RPM IP mode is selected. In this mode, revolutions per minute on 2- or
4-stroke engines can be measured using the Inductive Pickup on a spark plug wire.

3. . Displayed when dwell mode is selected.

4. . Displayed when duty cycle mode is selected.

5. 18 . Displayed when a certain number of cylinders is selected in the RPM IG or Dwell mode. Press the
“RANGE” button to toggle between 1, 2, 3, 4, 5, 6, 8, 10, 12 cylinder engines.

6. . Displayed when 4 strokes are selected in the RPM IP mode. Press the “RANGE” button to toggle
between 2-stroke and 4-stroke engines.

7. . Displayed when 2 strokes are selected in the RPM IP mode. Press the “RANGE” button to toggle
between 2-stroke and 4-stroke engines.

8. . Indicates that the value being displayed is the average of all readings taken since the Recording mode
was entered.

9. . Displayed when diode test is selected.

10. . Displayed when Relative mode is active.

11. . Displayed when Recording mode is active.

12. . Displayed when continuity test is selected.

13. . Displayed when the Hold mode is active.

14. . Displayed when the battery is low.

WARNING

TO AVOID FALSE READINGS, WHICH COULD LEAD TO POSSIBLE ELECTRIC SHOCK OR PERSONAL

INJURY, REPLACE THE BATTERY AS SOON AS THIS LOW BATTERY INDICATOR APPEARS.

15. . Indicates that the value being displayed is the maximum reading taken since the Recording mode
was entered.

16. . Displayed when autorange mode is active.

17. . Indicates that the value being displayed is the minimum reading taken since the Recording mode was
entered.

18. . Displayed when DC measurement function is selected.

19. . Displayed when AC measurement function is selected.

20. . Indicates negative readings. In Relative mode, this sign indicates that the present input is less than
the stored reference.

21. . Indicates that the automatic power-off feature has been enabled.

22. . Indicates that USB communication function has been turned on.

23. . Displayed when a – or + trigger slope is selected while the meter is in the RPM IP or RPM IG (Duty
Cycle, Pulse Width, Hz or Dwell) mode. The meter defaults to a – (negative) trigger slope. Press the “±
TRIG” button for 1 second to toggle between negative (-) and positive (+) trigger slope. Also displayed
when the bargraph indicates trigger level.

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24. . Indicates the polarity of the input.
Also indicates a – (negative) or + (positive) trigger slope when a trigger slope is selected.

HIGH TIME

LOW TIME

1 DUTY CYCLE

Select a negative (-) trigger slope to measure low (-) time and a positive (+) trigger slope to measure high
(+) time. For example, when measuring duty cycle of the Mixture Control Solenoid, the low (-) time is the
On time in most cases.

25. ANALOG DISPLAY SCALE. Displayed with 41-position analog pointers.

26. The following symbols indicate the unit of the value displayed:

DWL° The number of degrees of distributor rotation where the points remain closed,

measured for 1 to 12 cylinders

% Percent, used for duty cycle measurement

°C/°F Centigrade or Fahrenheit temperature measurement

Ω Ohms

kΩ

Hertz (1 cycle/sec)

Kilohertz (1 × 10 cycles/sec)

Volts

Millivolts (1 × 10 Volts)

Amperes (Amps)

Milliamperes (1 × 10 Amps)

Microamperes (1 × 10 Amps)

Microfarads (1 × 10 Farads)

Milliseconds (1 × 10 seconds)

Megohm (1 × 10 Ohms)

6

3

-3

-3

-6

-6

-3

3

Kilohm (1 × 10 Ohms)

MΩ

Hz

kHz

V

mV

A

mA

µA

µF

mS

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5. BASIC ELECTRICAL TESTS AND MEASUREMENTS

One of the most common electrical diagnostic tools is a digital multimeter (DMM). A DMM is simply an
electronic yardstick for making electrical measurements.

DMMs have many special functions and features, but the most common use is to measure voltage, current, and
resistance. An automotive multimeter such as this automotive multimeter can also measure frequency, RPM,
duty cycle, dwell, pulse width, temperature, capacitance, and even the condition of diodes.

General Considerations for Making Measurements

• Accuracy

A measurement range determines the highest value the meter can measure. Most Meter functions
have more than one range. When making a measurement, it is very important that you are in the right
measurement range. Selection of a lower range moves the decimal point one place to the left and increases
the accuracy of the readings. When the LCD shows OFL (overload), the range is too low; select the next
higher range.

• Analog Bargraph

The bargraph is useful for trend setting or directional data. It is easiest to read when the data causes the
digital display to change rapidly.

• Safety Shutter

When measuring voltage, be sure that the red test lead is connected to the
“ ” input jack; if the red test lead is connected to the “A” or “mA μA” jack, you may be injured or the
meter may be damaged. When measuring current, do not connect the red test lead to the “ ” input
jack. The safety shutters of the meter areused to prevent inadvertent connection to wrong input terminal.

Voltage Measurements

Voltage measurements are dynamic tests that measure the voltage across a circuit or component with the power
on. Voltage measurements are made with the test leads connected across the circuit element under test.

WARNING

TO AVOID ELECTRICAL SHOCK AND INSTRUMENT DAMAGE, INPUT VOLTAGE MUST NOT EXCEED

1000V DC OR 750V AC RMS. DO NOT ATTEMPT TO MEASURE ANY UNKNOWN VOLTAGE THAT

MAY EXCEED 1000V DC OR 750V AC RMS.

NOTE: When making voltage measurement, this meter must be connected in parallel with the circuit or circuit

element under test.

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Blac

kR

ed

Parallel Connection

12V Battery

Meter setup to measure voltage:

• Set the rotary switch to the voltage ( or m ) setting. (The m setting is only for DC millivolt

measurements.)

• Press the “DC/AC” button to select AC or DC voltage measurement, the display will show the corresponding

symbol.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

Back probe to the negative (-) circuit or to ground.

Red probe to the circuit coming from the power source.

Resistance Measurements

Resistance is a static measurement which means that it must be measured with the power off. It is measured in
Ohms (Ω) and the values can vary greatly from a few milliohms (mΩ) for contact resistance to billions of ohms
for insulators.

WARNING

TURN OFF POWER AND DISCHARGE ALL CAPACITORS IN THE CIRCUIT TO BE TESTED BEFORE MAKING

IN-CIRCUIT RESISTANCE MEASUREMENTS. ACCURATE MEASUREMENT IS NOT POSSIBLE IF EXTERNAL

OR RESIDUAL VOLTAGE IS PRESENT.

NOTE: The resistance in the test probes can affect accuracy in the 400 range. Short the probes together and

press the “REL” button to subtract test lead resistance from the measurement.

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RedBlack

Parallel Connection

Meter setup to measure resistance:

• Set the rotary switch to the Ω setting. The meter defaults to resistance measurement function.

• If a more accurate measurement is desired, select the proper resistance range by pressing the “RANGE”

button.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Test probes across the resistor or circuit to be tested.

Accuracy:

Rapidly changing display readings (noise) can sometimes be eliminated if you change to a higher range. You
can also smooth out noise somewhat by using the averaging (AVG) feature provided by the Recording function.

Continuity Test

A continuity test is a static test (circuit power off) that allows you to quickly and easily distinguish between
an open and a closed circuit. When the meter detects a closed circuit or short, it beeps so you do not have to
look at the meter during the test. This can be a valuable troubleshooting aid when determining good or blown
fuses and fusible links, open or shorted conductors and wires, operations of switches, etc. It is also helpful for
troubleshooting in out-of-the-way locations where it is difcult to watch the readout at all times.

NOTE: Turn off power to the circuit to be tested.

A beeper tone does not necessarily means zero resistance.

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RedBlack

OPEN CIRCUIT - NO BEEP

Meter setup to test circuit continuity:

• Set the rotary switch to the Ω setting.

• Press the “DWL” button until “ ” appears on the display. Now the meter is in continuity test function and

the meter defaults to the 400Ω range.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Test probes across the circuit to be tested.

If the circuit is closed (resistance < about 40Ω), the meter will beep. If the circuit is open (resistance > 150Ω),
there is no beep.

RedBlack

CLOSED CIRCUIT - BEEP SOUNDS

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Diode Test

A diode operates as an electronic switch to allow current to ow in one direction only. It turns on when the
voltage is over a certain level, generally greater than 0.3V for a silicon diode. The meter has a static diode test
mode to test diodes when the circuit power is off. Readings across a good diode will typically be greater than

0.3V in one direction, while indicating an open circuit in the other direction.

NOTE: Turn off power to the circuit to be tested.

RedBlack

Meter setup to test the diode:

• Set the rotary switch to the setting.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Black test probe to the cathode of the diode.

• Red test probe to the anode of the diode.

If the diode is good, the reading should indicate 0.3V to 0.8V on the display.

Reverse the probes. The display should show “OFL” if the diode is good.

NOTE: A defective diode may read OFL (OverFLow) or have the same reading in both directions no matter how

the test probes are connected.

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Current Measurements

Current measurements are dynamic tests that measure the current through a circuit or component with
the power on. Current measurements are made with the test leads connected in series with the circuit or
component under test.

CAUTION

TO AVOID DAMAGE TO THE METER, CURRENT SOURCES HAVING OPEN CIRCUIT VOLTAGES GREATER

THAN 1000V DC OR 750V AC MUST NOT BE MEASURED.

NOTE: When making current measurements, the meter must be connected in series with the circuit (or circuit

element) under test. To avoid damage to the meter or the equipment under test, never connect the test
probes across a voltage source when the meter is in current measurement function.

12V Battery

Red

Black

Meter setup to measure current:

• Set the rotary switch to a current (10 ,m , or μ ) setting.

• Press the “DC/AC” button to select AC or DC current measurement, the display will show the corresponding

symbol.

• Insert the black lead in the “COM” jack.

• If the current to be measured is between 400mA and 10A, insert the red test lead in the “A” jack. If the

current is less than 400mA, insert the red test lead in the “mA μA” jack instead.

• Turn off power to the circuit to be tested. Then discharge all high-voltage capacitors.

• Break the circuit path to be tested, creating a point where the test probes can be connected in series with

the circuit.

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Connect:

• Test probes in series with the circuit to be tested.

Turn on power to the circuit, then read the display. For DC current measurements, the polarity of the red test
lead connection will be indicated as well.

Note:

1. If the red lead is connected to the “A” jack, the rotary switch must be set in the 10 position. If the red
lead is connected to the “mA μA” jack, the rotary switch must be set in the m or μ position.

2. If the magnitude of the current to be measured is not known beforehand, select the highest range rst and

then reduce it range by range until satisfactory resolution is obtained.

Temperature Measurements

Temperature measurements can be made dynamically (power on) but care must be taken so the temperature
probe does not come in contact with voltage levels that might damage the probe or the meter.

CAUTION

DO NOT ALLOW TEMPERATURE PROBES TO CONTACT ANY VOLTAGE THAT

MAY EXCEED 30V AC, 42V PEAK OR 60V DC. KEEP THE METER AWAY FROM SOURCES

OF VERY HIGH TEMPERATURES TO PREVENT DAMAGE.

NOTE: To avoid possible damage to the meter or other equipment, remember that while the meter is rated

for -40°C to 1370°C and -40°F to 2,498°F, the K Type Thermocouple provided with the meter is
rated to 480°C. For temperatures out of that range, use a higher rated thermocouple. The K Type
Thermocouple provided with the meter is a present. For accurate measurements, use a professional­grade thermocouple.

K type
thermocouple

Object

TEMP

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Meter setup to measure temperature:

• Set the rotary switch to TEMP setting.

Note: The meter defaults to Celsius temperature measurement mode. You can press the “DC/AC” button to

switch between Celsius and Fahrenheit temperature measurement if necessary.

• Insert the plug of the K type thermocouple into the “COM” and “ ” jacks as shown, make sure that the

polarity connections are correct.

Connect:

• Tip of the K type thermocouple to the area or surface to be measured.

Read the reading on the display.

Capacitance (CAP) Measurements

Capacitance measurements check the condition of capacitors under static (power off) conditions in microfarads (µF).

CAUTION

TURN OFF POWER TO THE CIRCUIT TO BE TESTED. THOROUGHLY DISCHARGE THE CAPACITOR TO

BE TESTED BY SHORTING THE CAPACITOR LEADS TOGETHER. USE THE DC VOLTAGE FUNCTION TO

CONFIRM THAT THE CAPACITOR IS DISCHARGED.

NOTE: In the 1µF range, readings may be unstable due to environmentally induced electrical noise and

oating capacity of the test probes. Therefore, connect the capacitor directly to the input terminals.

Black Red

Parallel Connection

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Meter setup to measure capacitance:

• Set the rotary switch to the Capacitance

( ) setting.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Test probes to the capacitor. When measuring polarized capacitors, connect the red probe to the anode of

the capacitor and the black probe to the cathode of the capacitor.

Wait until the reading is stable, then review the reading on the display.

Hi-Sen Frequency (Hz) Measurements

This meter has two frequency measurement modes: the High-Sen (high sensitivity – trigger level of
about 250mV) mode for the general frequency counter mode and the Hz or RPM IG mode for automotive
measurement.

In the High-Sen Frequency counter mode, the meter autoranges to one of the four ranges: 200Hz, 2000Hz,
20kHz, and 200kHz.

If the input signal is below the trigger level, frequency measurements will not be taken. If your readings are
unstable, the input signal may be near the trigger level for that range. You can usually correct this by selecting
a lower range using the “RANGE” button. If your readings seem to be a multiple of what you expect, your input
signal may have distortion or ringing, which is common to signals from electronic motor controls. In this case,
use the Hz or RPM IG mode to get the correct readings.

Reference Voltage Side

Signal Output

Ground

Black Red

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Meter setup to measure frequency:

• Set the rotary switch to the Hi-Sen Hz ( ) setting.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Black test probe to ground.

• Red test probe to the signal output lead of the object to be tested.

NOTE: The display will show 0.00Hz for frequencies below 0.5Hz.

6. BASIC AUTOMOTIVE MEASUREMENTS

RPM Measurements Using the Inductive Pickup (RPM IP mode)

RPM (revolutions per minute) can be measured in the RPM IP mode using the inductive pickup (standard
accessory). Clamp the inductive pickup around any spark plug wire; the inductive pickup converts the
magnetic eld generated by the current ow in the spark plug wire into a pulse that triggers the meter’s RPM
measurement.

With the inductive pickup, you can make RPM measurements on any two- or four-stroke automotive engine with
any number of cylinders without physically connecting to any test points or wires.

WARNING

THE IGNITION SYSTEM POSES A POTENTIAL SHOCK HAZARD. ENSURE THAT THE ENGINE IS OFF

BEFORE CONNECTING OR REMOVING THE INDUCTIVE PICKUP.

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RPM IP

Inductive
Pickup

Black

Red

Spark

Plug

Distributor Cap

Conventional
Ignition Coil

Meter setup to measure RPM:

• Set the rotary switch to RPM IP (RPM IP) setting.

• Press the “RANGE” button to select either 2 or 4 stroke engine.

• Insert the black plug of the inductive pickup into the “COM” jack and the red plug of the inductive pickup

into the “ ” jack.

Connect the inductive pickup to any spark plug wire and start the engine. If no reading is received, unhook the
pickup, turn it over, and connect again. If the reading is too high or unstable, adjust trigger level.

NOTE: Position the pickup away from the distributor and the exhaust manifold, but as close as possible to

the spark plug. If no reading or an erratic reading is displayed, rst reverse the inductive pickup; then
move the pickup to another spark plug wire and test again.

RPM Measurements Using Test Probes (RPM IG mode)

RPM can be measured using the test probes connected to the primary side of a conventional distributor-type ignition
coil. Before measuring RPM, you need to determine whether you are looking at a 2- or 4-stroke engine and how many
cylinders are in the engine.

When the RPM IG setting is rst selected, the meter defaults to four strokes and four cylinders so that ,

, 4CYL, , and _ appear on the display. If you want to select a different number of cylinders, press the

“RANGE” button repeatedly to cycle through the number of cylinders between 1 and 12 (excluding 7, 9 and

11). The number of strokes can not be changed in the RPM IG mode; you must temporarily switch to the RPM

IP mode, then change strokes by pressing the “RANGE” button, and then return to the RPM IG mode.

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WARNING

THE IGNITION SYSTEM POSES A POTENTIAL SHOCK HAZARD. ENSURE THAT THE ENGINE IS OFF

BEFORE CONNECTING AND REMOVING THE TEST PROBES.

Conventional

Ignition Coil

Spark Plug

Black

Red

RPM IG

Meter setup to measure RPM:

• Set the rotary switch to the RPM IG (RPMIG) setting.

• If “RPM IG” is not present on the display, press the “%DUTY” button until “RPM IG” appears on the display.

• Press the “RANGE” button to select the number of cylinders.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Black test probe to a good ground near the coil.

• Red test probe to the primary side of the ignition coil.

Start the engine and note the reading on the display while moving the throttle.

If the reading is too high or unstable, adjust the trigger level.

NOTE: Refer to the car’s service manual for information on the number of strokes and cylinders for specic

engines.

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Duty Cycle Measurements

Duty cycle (or duty factor) is the percentage of time a signal is above or below a trigger level during one cycle.
There are many signals on the vehicle where you may need to measure duty cycle. For example, signals from
the mixture control solenoid of a feedback carburetor, signals from cam or crank sensors, and the control
signals for fuel injectors. This example uses the meter to measure duty cycle on the mixture control solenoid
signal of a feedback carburetor.

Black

Good
ground

Red

Jumper leads
from feedback
solenoid

RPM IG

Meter setup to measure duty cycle:

• Set the rotary switch to the RPM IG (RPMIG) setting.

• Press the “%DUTY” button until “%” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Jumper wires between the feedback solenoid and the harness connector.

• Black test probe to a good ground near the carburetor or the negative (-) vehicle battery post.

• Red test probe to the solenoid control signal.

Press and hold down the “±TRIG” button for 1 sec to toggle between negative (-) and positive (+) slope.

Start the engine. A duty cycle of about 50% should be read.

If reading is too high or unstable, adjust the trigger level by pressing the “±TRIG” button repeatedly.

For most cars, the points of the solenoid are closed for a duty cycle between 50% and 70%.

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Once the engine warms up and goes into open loop, the duty cycle should uctuate.

NOTE: Refer to the car’s service manual to verify slope for each component.

Pulse Width Measurements

Pulse width is the length of time an actuator is energized. For example, fuel injectors are activated by an
electronic pulse from the Engine Control Module (ECM). This pulse generates a magnetic eld that pulls the
injector nozzle valve open. The pulse ends and the injector nozzle closes. This Open-to-Close time is the pulse
width and is measured in milliseconds (mS).

Automotive applications for measuring pulse width include fuel, fuel mixture control solenoids and the idle air
control motor. The following example shows how to measure pulse width on port fuel injectors.

RPM IG

Black

Good
ground

Red

Jumper leads
from feedback
solenoid

Meter setup to measure pulse width:

• Set the rotary switch to the RPM IG

(RPM IG) setting.

• Press the “%DUTY” button until “mS” appears on the display.

• Press and hold down the “±TRIG” button for 1 sec until the negative (-) trigger slope is displayed.

NOTE: The On time for most fuel injectors is displayed on the negative (-) slope.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

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Connect:

• Jumper wires between the fuel injector and the harness connector.

• Black test probe to a good ground near the fuel injector or the negative (-) vehicle battery post.

• Red test probe to the fuel injector solenoid driver input on the jumper cable.

Start the engine. Pulse width is shown in milliseconds.

If reading is too high (overrange) or unstable, adjust the trigger level by pressing the “±TRIG” button repeatedly.

Frequency (Automotive Hz) Measurements

Frequency is the number of cycles a signal completes each second. There are many sensors and signals on
a vehicle that produce a frequency that can be measured. For example, wheel speed sensors, vehicle speed
sensors, fuel injector control signals, cam and crank outputs, and engine reference signals. This example
measures the frequency output of a digital mass air ow sensor (MAF). Output can vary from several hundred
Hz to ten thousand Hz depending on the type of MAF sensor.

NOTE: Although similar in appearance, MAF sensors made by different manufacturers function differently,

have different frequency ranges and squarewaves, and are not interchangeable. Voltage level of
squarewaves should be consistent. Frequency should change smoothly with engine load and speed.

RPM IG

Black

Black lead
to the MAF
signal ground

Red lead to
the MAF

signal output

Jumper leads
from MAF
sensor

Red

Meter setup to measure frequency:

• Set the rotary switch to the RPM IG (RPMIG) setting.

• Press the “%DUTY” button until “Hz” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

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Connect:

• Jumper wires between the MAF sensor and the harness connector.

• Black test probe to the ground jumper wire.

• Red test probe to the signal output jumper wire.

Start the engine. Note the frequency shown on the meter display at idle. Advance the throttle and note the
change in frequency.

NOTE: Refer to the car’s service manual for correct frequency readings.

If reading is unstable, adjust the trigger level by pressing the “±TRIG” button repeatedly.

Dwell Measurements

Dwell is the number of degrees of distributor rotation that the points remain closed. Dwell can be measured for
1, 2, 3, 4, 5, 6, 8, 10, or 12 cylinder engines using the meter. Before measuring dwell, you need to determine
how many cylinders are in the engine.

In the Dwell mode, the meter defaults to four cylinders and negative (-) slope, so ,
4CYL, , and _ are displayed. If you want to select a different cylinder number, press the “RANGE” button
repeatedly to select the correct number of cylinders.

RPM IG

Breaker Pointers/

Ignition Module

Black

Red

Good
Ground

Meter setup to measure dwell:

• Set the rotary switch to the RPM IG (RPMIG) setting.

• Press the “DWL” button until “ ”, “4CYL”, “ ”, and “

_

” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

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Connect:

• Black test probe to a good ground or the negative (-) vehicle battery post.

• Red test probe to the wire that connects to the breaker points.

Press the “RANGE” button repeatedly to select the required number of cylinders.

Start the engine and observe the reading.

If the reading is too high or unstable, adjust trigger level by pressing the “±TRIG” button repeatedly.

7. BASIC AUTOMOTIVE DIAGNOSTIC TESTING

A systematic series of tests that check the vehicle electrical system should be performed before testing
individual automotive components. The following basic tests check the primary areas responsible for the
majority of the electrical problems found in an automobile. Perform these tests rst, even if a fault or trouble
code is set in the on-board computer. A basic ground problem in the electrical system can cause a component
malfunction detected by the on-board. If the problem is caused by a poor ground, simply replacing a failed
component will not provide a cure.

Basic diagnostic testing should begin by checking the main source of power and the chassis ground circuit
connections. Ground circuits are potentially the most troublesome areas of automotive electronics, yet they are
least understood and hardest to diagnose. One of the most frustrating electrical problems you will encounter
in an automobile is a high-resistance ground. This can create some very strange symptoms that seem to be
unrelated to the cause. The symptoms can include problems with turn signals, lights that stay dim, the wrong
lights turning on, transmission shifting problems, gauges that change when certain accessories are operated, or
even lights that will not turn on at all.

You can nd a bad ground by checking the voltage drop between the component’s ground wire and a clean
chassis ground or the negative vehicle battery terminal. An excessive voltage drop in a ground circuit affects the
entire electrical circuit. That is why it is so important to make sure the basic circuits are in good shape before
checking trouble codes in the on-board computer and individual components.

BATTERY TESTS

If you are having electrical problems, rst test the battery. If the battery is low or discharged, it must be
thoroughly recharged before tests can begin.

A discharged battery may also indicate a problem in the charging circuit. Batteries are often blamed for “no­start” conditions when, in fact, the real problem exists in the charging system. After a charging system problem
exists for some period of time, the battery becomes discharged and can not supply enough current for the
starter to crank the engine.

Many electrical problems are caused by current drains and shorts. Current drains that cause dead batteries are
often referred to as shorts, even though they are not actually short circuits. Shorts that blow fuses can be found
using the same troubleshooting techniques used to nd current drains, even though the symptoms are different.

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NOTE: Remove the battery cables and thoroughly clean the cable terminals and the battery posts. Reassemble

them before beginning tests.

CAUTION

THE IGNITION SWITCH MUST BE OFF TO PREVENT DAMAGE TO THE VEHICLE COMPUTER WHEN

CONNECTING OR DISCONNECTING BATTERY CABLES.

Battery Surface Discharge Test

The test checks for a low current discharge across the battery case. Dirt, moisture, corrosion are typical causes
of surface discharge. Clean the battery surface with a baking soda and water solution to prevent surface
discharge. However, never let the solution get into the battery.

Positive
battery
cable

Negative
battery
cable

Black

Red

12V battery

Meter setup to measure surface discharge:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Press the “REC” button (selects the MAX.MIN.AVG function).

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

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Connect:

• Black test probe to the negative (-) battery post.

• Red test probe to the battery case around the positive (+) battery post: DO NOT TOUCH THE POST.

A reading of more than 0.5V indicates excessive surface discharge.

Clean the battery surface thoroughly if this has not been done and retest.

If you continue to get a reading of more than 0.5V, the battery is defective and should be replaced.

Battery No-Load Test

A fully charged battery will display at least 12.6V. The following test checks for battery charge state. Since
voltage tests only show the charge state and not the battery condition, you should also perform a load test to
indicate the battery’s performance.

CAUTION

THE IGNITION SWITCH MUST BE OFF WHEN CONNECTING OR DISCONNECTING BATTERY CABLES TO

PREVENT DAMAGE TO THE VEHICLE COMPUTER.

Positive
battery
cable

Negative
battery
cable

Black

Red

12V battery

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Meter setup to check battery charge state:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Turn the headlights on for 30 seconds to dissipate any battery surface charge.

Disconnect the negative (-) battery cable from the negative battery terminal.

Connect:

• Black test probe to the negative (-) battery post.

• Red test probe to the positive (+) battery post.

Press the “REC” button (selects the MAX.MIN.AVG function).

A minimum reading of less than 12.4V indicates an undercharged battery. Recharge before further testing.

No Load 12V Battery Test

Meter Reading % Battery Charge

12.60V or greater 100%

12.45V 75%

12.30V 50%

12.15V 25%

Note: This table is only for non-critical reference.

Battery Parasitic Load Test

Each vehicle has a certain amount of parasitic load that is considered normal, but any current drain that
exceeds that amount should be located and stopped. On newer vehicles after the introduction of electronic
ignition and computer control systems, the parasitic load can be as high as 100mA. Check the manufacturer’s
specications for the acceptable level of parasitic load for a specic vehicle.

WARNING

DO NOT CRANK THE ENGINE OR TURN ON ACCESSORIES THAT DRAW MORE THAN 10A COMBINED

DURING THIS TEST SINCE YOU COULD DAMAGE THE METER OR INJURE YOURSELF.

CAUTION

THE IGNITION SWITCH MUST BE OFF WHEN CONNECTING OR DISCONNECTING BATTERY CABLES TO

PREVENT DAMAGE TO THE VEHICLE COMPUTER.

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Red

Black

Negative
battery
cable

Remove fuses
one at a time

Meter setup to measure parasitic load:

• Set the rotary switch to amps (10 ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “A” jack.

Turn the ignition switch and all accessories off.

Disconnect the negative (-) battery cable from the negative battery terminal.

Connect:

• Black test probe to the disconnected negative (-) battery cable terminal.

• Red test probe to the negative (-) battery post.

Press the “REC” button (selects the MAX.MIN.AVG function).

If excessive parasitic draw outside range specied in the vehicle’s service manual is indicated, remove
the circuit fuses from the fuse box one at a time until theexcessive draw is located. Also check non-fused
applications such as headlights, computer relays, andcapacitors in the instrument panel.

NOTE: Many vehicle computers draw 10mA or more continuously.

Turn off ignition and reconnect the battery.

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Battery Voltage Load Test

This test checks the battery’s capacity to deliver sufcient cranking voltage.

12V Battery

Red

Black

Meter setup to measure voltage load:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Black lead to the negative (-) battery post.

• Red lead to the positive (+) battery post.

Press the “REC” button (selects the MAX.MIN.AVG function).

Disable the ignition so that the engine can’t start and crank the engine for 15 seconds. Check the minimum
reading.

A reading of less than 9.40V at 60°F/16°C indicates a weak battery. Recharge or replace the battery before
testing.

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Voltage Load Test Battery Voltage Vs Battery/Air Temperature

Meter Reading Battery/Air Temperature

10.0V 90°F/33°C

9.8V 80°F/27°C

9.6V 70°F/21°C

9.4V 60°F/16°C

9.2V 50°F/10°C

9.0V 40°F/4°C

8.8V 30°F/-1°C

8.6V 20°F/-7°C

NOTE: The above table is only for non-critical reference.

Battery temperature can be checked by using the meter’s temperature function.

VOLTAGE DROP TESTS

Voltage drop tests measure the amount of voltage expended to overcome resistance (an opposing force to
the ow of electrical current created by a circuit or component); the lower the voltage drop reading, the less
resistance in the circuit under test.

The Hold function and the MAX/MIN Record function are very useful for measuring voltage drops on many
different components and connections. For example, measuring the voltage drop across the connections and
components in the starter circuit while cranking the engine (ignition or fuel system disabled to prevent starting)
allows you to determine if there is excess resistance in the starter circuit.

To measure voltage drop, current must be owing in the circuit and both voltage test probes must be connected
on the same side of the circuit. Voltage drop can also be determined from available voltage readings by noting
the difference between each successive reading.

Refer to the vehicle manufacturer’s specication for voltage drop information. If the voltage drop specication
is not available, refer to the following table to determine typical voltage drop for 12V systems:

Typical Allowable Voltage Drop

Component Typical Voltage Drop

Battery cable length up to 3 feet 0.1V

Battery cable length over 3 feet 0.2V

Magnetic switches 0.3V

Solenoid switches 0.2V

Mechanical switches 0.1V

Battery cable connectors 0.05V

Connections 0.0V

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NOTE: The allowable voltage drop values listed in the table do not apply to circuits that use aluminum cables.

Normally, maximum voltage drop should not be more than 0.1V per wire, ground, connection, switch, or
solenoid. You can determine the typical voltage by adding up the values from the above table. For example, the
typical voltage drop from the negative battery post to the starter drive housing (negative test probe connected to
the negative battery post and the positive test probe connected to the starter drive housing) should not exceed

0.4V. This connection consists of two connectors, one wire, and two grounds.

If the voltage drop reading is within the allowable maximum voltage drop specication, the circuit’s resistance
is acceptable.

If the voltage drop reading exceeds the maximum allowable voltage drop, the point of excessive resistance can
be located by checking the voltage reading at each connection and cable end. When a sharp decrease in voltage
drop is observed, the cause of the excessive resistance is located between that test point and the previous test
point.

Battery Ground to Engine Block Voltage Drop Test

This test checks for engine ground efciency.

Engine
Block

12V Battery

Red

Black

Setup to check voltage drop:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Touch the black test probe to the negative (-) battery post and the red test probe to the positive (+) battery post;
this reading is the base voltage to compare your test voltage reading against.

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Connect:

• Red test probe to a clean spot on the engine block.

Press the “REC” button (selects the MAX.MIN.AVG function).

Disable the ignition so the engine can’t start and crank the engine for four to ve seconds.

This connection has two connectors, one wire, one ground and one cable terminal-to-battery post; a voltage
drop of more than 0.5V indicates a poor ground circuit.

Clean and inspect the battery cable connections and the ground connection and test again.

NOTE: Repeat the test after the engine has thoroughly warmed up. Heat expansion may change voltage drop.

Negative Chassis Ground Efficiency Voltage Drop Test

This test checks for chassis ground efciency.

12V Battery

Red

Black

Engine
Block

Chassis
Ground

Meter setup to check voltage drop:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Touch the black test probe to the negative (-) battery post and the red test probe to the positive (+) battery post;
this reading is the base voltage to compare your test voltage reading against.

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Connect:

• Black test probe to the negative (-) battery post.

• Red test probe to the point on the fender, re wall, or vehicle frame where the accessory ground is

fastened.

Press the “REC” button (selects the MAX.MIN.AVG function).

Turn on all the accessories (headlights, A/C fan, defroster, windshield wiper, etc.).

Disable the ignition so the engine can’t start and crank the engine for four to ve seconds.

This connection has two connectors, one wire, one ground and one cable terminal-tobattery post; a voltage drop
of more than 0.5V indicates a poor ground circuit.

Clean and inspect the battery cable connections and the ground and test again.

NOTE: Repeat the test after the engine has thoroughly warmed up. Heat expansion may change voltage drop.

Battery Ground to Starter Solenoid (+) Voltage Drop Test

This test checks for battery power efciency to the starter solenoid. Measure the voltage drop between the
battery post and the connecting cable, the solenoid post (+), and the wire that attaches to it.

Red

Black

Solenoid

12V Battery

Starter Motor

Meter setup to check voltage drop:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

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• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Touch the black test probe to the negative (-) battery post and the red test probe to the positive (+) battery post;
this reading is the base voltage to compare your test voltage reading against.

Connect:

• Black test probe direct to the positive (+) terminal on the starter solenoid.

• Red test probe to the positive (+) battery post.

Press the “REC” button (selects the MAX.MIN.AVG function).

Disable the ignition so the engine can’t start and crank the engine for four to ve seconds.

This connection has two connectors and one wire; a voltage drop of more than 0.3V indicates a poor circuit.

Clean and inspect the battery cable connections and ground and test again.

NOTE: Repeat the test after the engine has thoroughly warmed up. Heat expansion may change voltage drop.

Battery Ground to Complete Starter Circuit (+) Voltage Drop Test

This test checks for battery power efciency to the starter motor system including the starter solenoid. Even a
very low resistance in the starter circuit can cause the starter to turn slowly because of the high currents in the
starter circuits.

Starter Motor

Red

Black

Solenoid

12V Battery

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Meter setup to measure voltage drop:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Touch the black test probe to the negative (-) battery post and the red test probe to the positive (+) battery post
to establish the base voltage to compare the test voltage against.

Connect:

• Black test probe direct to the positive (+) terminal on the starter motor.

• Red test probe to the positive (+) battery post.

Press the “REC” button (selects the MAX.MIN.AVG function).

Disable the ignition so the engine can’t start and crank the engine for four to ve seconds.

This connection has four connectors, two wires, and two solenoid connections; a voltage drop of more than

0.8mV indicates a poor circuit.

Clean and inspect the battery, starter cables, solenoid, and cable connections and test again.

A defective starter solenoid may cause an excessive voltage drop. Check the cables and connections before
replacing the solenoid.

NOTE: Repeat the test after the engine has thoroughly warmed up. Heat expansion may change voltage drop.

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Starter Motor Current Test

If you have successfully completed the battery tests and the voltage drops tests, you have veried that there is
adequate battery voltage to the starter. Next, investigate how much current the starter is drawing by using a DC
clamp-on current probe. Under normal operating conditions, with an outside air temperature of 70°F, a good
rule of thumb for calculating cranking current is 1A per CID (Cubic Inch Displacement) or 60A per liter ± about
25%. Under no-load conditions, it’s 0.5A per CID ± about 10%. Check the manufacturer’s specications for
the correct starter cranking current.

Starter Motor

Red

Black

Meter setup to measure starter current:

• Set the rotary switch to the millivolts DC (m ) setting.

• Connect a DC clamp-on current probe (optional accessory) to the meter. Black lead to the “COM” jack and

red lead to the “ ” jack.

Clamp the clamp-on current probe around the cable connected to the positive (+) terminal of the starter motor.
Be sure that the arrow on the clamp is pointed in the direction of the current ow in the cable.

Press the “REC” button (selects the MAX.MIN.AVG function).

The minimum reading is the negative current draw.

Disable the ignition so the engine can’t start and crank the engine for four to ve seconds.

If the current draw is not high and the battery has tested good in the previous tests but the starter turns the
engine slowly, check the resistance (or voltage drop) in the starter circuit again.

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CHARGING SYSTEM TESTS

Charging system problems are often indicated by a “no-start” complaint. Normally, the battery has discharged
and the starter will not crank the engine. To properly check the charging system, the battery must be fully
charged. Recharge the battery completely if necessary, before continuing.

To diagnose and adjust regulators/alternators on a typical GM vehicle, you must rst determine if the system
has an integral (internal) regulator. Then determine whether it is a type A or B alternator. The type A alternator
has one brush connected to the battery (+) and the other brush grounded through the regulator. The type B
regulator has one brush tied to ground and the other connected to the battery (+) through the regulator. Next
isolate the problem to either the alternator or regulator. To do this, you need to by-pass the regulator (this is
called “full elding “), ground the type A eld terminal, or connect the type B eld terminal to the battery (+)
side. If the system now charges, the regulator is faulty.

Alternator Output Voltage Test at the Battery (+)

This test checks for alternator output voltage to the battery.

WARNING

WHEN PERFORMING THIS TEST, IDLE THE ENGINE WITH THE LIGHTS ON SO THE OUTPUT VOLTAGE

DOES NOT GO OVER 15V. IF CHECKING AN ALTERNATOR WITH AN INTEGRAL REGULATOR, YOU MUST

KNOW WHICH TYPE YOU ARE TESTING TO AVOID ANY DAMAGE TO THE ALTERNATOR OR REGULATOR

(SEE PREVIOUS DISCUSSION).

Red

Black

12V Battery

Engine
Block

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Meter setup to measure alternator output voltage:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Turn all vehicle accessories off.

Connect:

• Black lead to the negative (-) battery post.

• Red lead to the positive (+) battery post.

Press the “REC” button (selects the MAX.MIN.AVG function).

Start the engine and run it at 2,000 RPMs. A reading of 13.5V to 15.5V is an acceptable charging rate.

If the voltage is low, check for:

• Defective alternator or regulator (see tests that follow)

• Cracked, glazed, or loose drive belt

• Faulty or loose wires or connectors

Alternator Output (+) Voltage Test (Loaded)

This test is necessary only if the vehicle failed the previous test.

Red

Black

12V Battery

Alternator Output

(by-passed regulator)

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Meter setup to measure alternator output voltage:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Press the “REC” button (selects the MAX.MIN.AVG function).

Connect:

• Black test probe to the negative (-) battery post.

• Red test probe to the battery (+) terminal on the back of the alternator.

Start the engine and run it at 2,000 RPMs. A reading of 13.5V to 15.5V is an acceptable charging rate.

A good alternator will maintain at least 13.6V at the rated current output.

Alternator Field Current Test

Corroded or worn brushes (or terminals) limit the alternator’s eld current and cause a low alternator output
current. To check the eld current, load the alternator to the rated output current with a battery load tester and
measure the eld current by using a DC clamp-on current probe (optional accessory) or use the “A” input jack
on the meter.

Red

Black

12V Battery

Positive
Alternator

Cable

Meter setup to measure alternator field current:

• Set the rotary switch to amps (10 ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “A” jack.

Turn all vehicle accessories off.

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Connect:

• Black test probe to the positive (+) battery post.

• Red test probe to the positive (+) alternator cable.

Start the engine and run it at 2,000 RPMs. The current reading should be from 3A to 7A.

NOTE: Low battery voltage produces a higher current.

Alternator Diode Test

The diode pack in an alternator consists of two diodes in series. To test the alternator diodes, remove the diode
pack from the alternator. Then touch one test probe to one side of the alternator diode pack and touch the other
test probe to the other side. Record the reading; then reverse the test probes and repeat the test. For one of the
diode tests, the meter should display the voltage drop across the series diodes at typically about 0.8V; testing in
the other direction should display OFL (OverFLow). If the reading is about 0.4V, one diode is shorted. A reading
below 0.2V indicates two shorted diodes.

NOTE: Shorted diodes in the alternator can cause a low current output and run the battery dead overnight.

Red

Black

Anode

Cathode

Diode
Pack

Meter setup to measure voltage drop of the alternator diode pack:

• Set the rotary switch to diode test ( ) setting.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Disconnect the battery cable from the alternator output terminal.

Dismantle the alternator and remove the diode pack from the alternator.

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Connect:

• Black test probe to the negative (cathode) side of the diode pack.

• Red test probe to the positive (anode) side of the diode pack.

If neither diode is shorted, about 0.8V should be displayed.

If one diode is shorted, about 0.4V should be displayed.

If wire is open, both diodes are open, or the voltage drop is above 2V, OFL (OverFLow) should be displayed.

IGNITION SYSTEM TESTS

If you suspect a bad ignition wire, test resistance of the wire while moving, twisting, or bending the wire. The
resistance values will typically be around 10kΩ per foot.

If you suspect a problem with the ignition coil, check the resistance of the ignition coil’s primary and secondary
windings. This test needs to be done both when the coil is hot and when it is cold. You should also measure
from the coil’s case to each connector and between the primary and secondary windings to insure they are not
shorted together. The primary windings should have a very low resistance – typically from a few tenths of an
ohm to a few ohms. The secondary windings should have a much higher resistance – typically in the 10kΩ
range. To get the actual gures for a specic coil, check the manufacturer’s specications.

Spark Plug Wire (Secondary Ignition Wire) Resistance Test

WARNING

TO AVOID ELECTRICAL SHOCK, ALWAYS DISCONNECT THE IGNITION COIL FROM

THE IGNITION SYSTEM BEFORE TESTING.

If spark plugs are more than two years old or if there are other indications of ignition system problems, check
the spark plug wires.

NOTE: Be careful when pulling the spark plug boot from the insulator as bonding may have occurred.

This test checks for high resistance or open circuits in the secondary ignition wires (spark plug wires).

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Red

Black

Meter setup to measure spark plug wire resistance:

• Set the rotary switch to resistance (Ω ) setting.

• If “ ” is present on the display, press the “DWL” button until “ ” disappears.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Test probes to opposite ends of the spark plug wire.

Press the “REC” button (selects the MAX.MIN.AVG function).

The reading is dependent on the length of the wire you are measuring. Typical measurements are approximately
10kΩ per foot of wire. For example, two feet of spark plug wire should measure about 20kΩ .

Compare readings to other spark plug wires on the same engine to insure accuracy of the test.

NOTE: Be sure the test probe tips make contact with the center conductor of the wire.

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Primary Windings Resistance Test

This test checks for resistance in the primary windings of conventional and DIS (distributorless) ignition coils.

Red

Red

Black

Black

GM DIS
Ignition Coil
(TYPE II)

Conventional
Ignition Coil

Meter setup to measure resistance in the primary windings of ignition coils:

• Set the rotary switch to resistance (Ω ) setting.

• If “ ” is present on the display, press the “DWL” button until “ ” disappears.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Disconnect the coil from the ignition system.

Connect:

• Black test probe to the negative (-) terminal on the coil.

• Red test probe to the positive (+) terminal on the coil.

NOTE:

Both primary connections are located on the back of Type II coils.

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Typical measurements should be between 0.5Ω and 2.0Ω .

To get the actual gures for a specic coil, check the manufacturer’s specications.

NOTE: Test the ignition coil both when it is hot and when it is cold.

Secondary Windings Resistance Test

This test checks for resistance in the secondary windings of the conventional and DIS (Distributorless Ignition
System) ignition coils.

Red

Red

Black

Black

GM DIS
Ignition Coil
(TYPE II)

Conventional
Ignition Coil

Meter setup to measure resistance in the secondary windings of ignition coils:

• Set the rotary switch to resistance (Ω ) setting.

• If “ ” is present on the display, press the “DWL” button until “ ” disappears.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

• Disconnect the coil from the ignition system.

Connect:

• Black test probe to the high-tension terminal on the coil.

• Red test probe to the positive (+) terminal on the coil.

Typical measurements are between 6kΩ and 20kΩ.

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To get the actual gures for a specic coil, check the manufacturer’s specications.

NOTE: Test the ignition coil both when it is hot and when it is cold.

Condensers/Capacitors Leakage Test

This meter can be used to check automotive condensers (capacitors) using the Resistance function. Since
the Resistance function applies a voltage across the test leads, the condenser charges up and the displayed
resistance increases to innity. Any other reading indicates that you should replace the condenser.

CAUTION

BEFORE PERFORMING THIS TEST, MAKE SURE THAT IGNITION SYSTEM IS OFF AND ALL WIRES

CONNECTED TO THE COILS ARE DISCONNECTED.

Condenser

Red

Black

Meter setup to check condenser leakage:

• Set the rotary switch to resistance (Ω ) setting.

• If “ ” is present on the display, press the “DWL” button until “ ” disappears.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Black test probe to the negative (-) side of the condenser.

• Red test probe to the positive (+) side of the condenser.

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Watch the bargraph increase as the condenser charges. The resistance of a good condenser should increase
from zero to innity over a short period of time.

NOTE: In a conventional ignition system, make sure that the points are open before starting the test. Switch

the test leads and check the condenser in both directions. Check condensers under both hot and cold
conditions. The meter’s capacitance measurement function can be used to measure the capacitance
ofcondensers.

POSITION SENSORS

There are basically two types position sensors: Magnetic and Hall-Effect. The magnetic type is simply a
permanent magnet with a coil of wire wrapped around it. Magnetic sensors have two wires – one connected
to each end of a coil winding. Magnetic sensors can be found in some distributors and consist of a magnetic
pickup and a reluctor to change the magnetic eld. In a distributor, the clearance between the pickup and the
reluctor on a magnetic sensor is critical; be sure to check according to the manufacturer’s specications. The
specs are usually between 0.03 inches and 0.07 inches.

A Hall-Effect sensor uses a semiconductor material that produces a voltage as a magnetic eld passes
throughit. The voltage produced by the Hall-Effect sensor is proportional to the strength of the magnetic eld.
This magnetic eld can come from a permanent magnet or an electric current. Hall-Effect position sensors
have replaced ignition points in many distributor type ignition systems. They are also currently being used
to determine the crank and cam position on distributorless ignition system (DIS), which tells the vehicle’s
computer when to re the coils. This position information also tells the computer when to open the injectors
onsequential fuel injected systems.

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Magnetic Position Sensor (Pulses) Test

This test checks for pulses from a magnetic distributor pickup to determine if the reluctor wheel or the
magnetic pickup is bad.

Red

Reluctor

Magnetic
Pickup
Coil

Black

Meter setup to check pulses from a magnetic pickup:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Disconnect the distributor from the ignition module.

Connect:

• Test probes to the sensor output leads.

Watch the bargraph change. When the engine is cranked, pulses should appear on the bar graph.

No pluses will appear if the reluctor wheel or the magnetic pickup is bad.

NOTE: Clearance between the pickup and the reluctor is very critical. Be sure to check it according to the

manufacturer’s specications.

On GM cars, remove the distributor cap to access the pickup and the reluctor.

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Hall-Effect Sensor (Voltage) Test

This test checks for switching action of the Hall-Effect position sensor.

Red

Fixed position
magnet

Signal
output (+12V)

Hall-Effect
device

Switching
transistor

Insert a thin
metal blade

between Hall-

Effect device
and magnet

Connect

to battery

Black

Meter setup to check Hall-Effect sensors:

• Set the rotary switch to voltage ( ) setting.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Connect:

• Black test probe to the ground terminal of the Hall-Effect sensor.

• Red test probe to the signal output terminal of the Hall-Effect sensor.

Insert a thin metal blade or steel feeler gauge between the Hall-Effect device and the magnet while watching
the bargraph and the display.

The output signal should vary from 12V to 0V. Inserting the metal blade blocks the magnetic eld from getting
to the Hall-Effect sensor; removing the metal blade allows the magnetic eld to reach the sensor.

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8. BASIC AUTOMOTIVE COMPONENT TESTING

Computer Controlled Systems

Most cars built today have several on-board computers that control the engine, transmission, brake, suspension,
climate control, entertainment, and many other systems.

Control systems of computerized vehicle are made up of the following three basic component groups:

• Sensors. Input devices to provide feedback for the vehicle computer. For example, coolant sensor, vacuum

sensor, throttle position sensor, RPM senor, barometric sensor, oxygen sensor, etc.

• Engine Control Module (ECM). Processes feedback supplied by the sensors and then sends an electronic

command to the relevant component actuators.

• Actuators. Output devices that may be mechanical, electrical, or vacuum components activated by the

vehicle computer. For example, electro-mechanical carburetor, fuel injector, ignition spark advancer, air
pump, exhaust gas recirculation valve, canister purger, torque converter clutch, etc.

Sometimes when a sensor or actuator fails, an error code is generated. These errors are stored in the
computer memory as fault or trouble codes. Each sensor has various code numbers assigned to it,
depending on the problem that occurred.

When a fault occurs, a technician can read the fault codes by retrieving the information from the
computer’s memory. There are various ways to read these trouble codes. On vehicle model years 1995 or
older, they may display the fault codes using the digital clock on the dash, others use the tachometer, and
many use a blinking light to signal the fault codes. However, vehicle model years 1996 or newer which use
the OBD II protocol require a code reader or scan tool that plugs into the computer’s serial communication
port to read the trouble codes.

NOTE: For specic instructions on how to retrieve trouble codes from a specic vehicle computer system,

consult the service manual for the vehicle.

Basic Component Testing

Testing with specic components often requires detailed component schematics and test specications
provided by the vehicle manufacturer. The following section provides general test information and procedures
for the primary input devices (sensors) and output devices (actuators).

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INPUT DEVICE (SENSORS) TESTS

Temperature Tests

To test many components (such as radiators, transmissions, heaters, A/C condensers, A/C evaporators, engine
coolant sensors, coolant temperature switches, and air temperature sensors) that regulate temperature, measure
the surface temperature of the area surrounding the component.

Radiator

K type

Thermocouple

Meter setup to measure temperature:

• Set the rotary switch to temperature (TEMP) setting.

• Insert the plug of the K type thermocouple into the “COM” and “ ” jacks as shown, make sure that the

polarity connections are correct.

• Press the “REC” button (selects the MAX.MIN.AVG function).

Touch the tip of the thermocouple directly to the surface area near the radiator inlet.

Press the “DC/AC” button to switch between °F and °C.

Refer to the manufacturer’s specications for correct temperature. Measured temperature should be within
±10°F (±5°C) of the specications.

NOTE: The above procedure is specic to testing radiator temperature. Use similar test procedures to measure

temperature of other components or systems.

Two-Wire Device (Thermistor) Tests

Thermistors are essentially variable resistors that are sensitive to temperature level changes. The thermistor’s
resistance value changes as the temperature changes. Typical thermistor applications are: Engine Coolant
Temperature (ECT) sensor, Air Charge Temperature (ACT) sensor, Manifold Air Temperature (MAT) sensor, Vane
Air Temperature (VAT) sensor, and Throttle Body Temperature (TBT) sensor, etc.

A thermistor can be tested by checking resistance change or voltage change. A quel de Evaick and easy way to
monitor change is with the bargraph on the meter.

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Thermistor Resistance Change Test

Black

Red

Meter setup to check resistance change of thermistors:

• Set the rotary switch to resistance (Ω ) setting.

• If “ ” is present on the display, press the “DWL” button until “ ” disappears.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

Disconnect the sensor connector.

Connect:

• Black test probe to the negative (-) terminal of the sensor.

• Red test probe to the positive (+) terminal of the sensor.

Resistance reading should match the temperature of the sensor.

NOTE: Refer to the manufacturer’s specications for resistance vs temperature for the sensor.

Temperature can be checked using the previous procedure.

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Thermistor Voltage Change Test

Black

Red

Meter setup to measure voltage change of a thermistor:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

• Press the “REC” button (selects the MAX.MIN.AVG function).

Disconnect the sensor connector. Connect jumper wires between the connector and the sensor.

Connect:

• Black test probe to the negative (-) circuit from the sensor.

• Red test probe to the circuit coming from the power source.

Start the engine. The voltage should change as the temperature changes.

Refer to the manufacturer’s specications. If the voltage change is not within specications, check for sources
of excessive resistance before replacing thermistor: poor connectors, connections, or breaks in the wiring.

NOTE: Temperature can be checked using the meter’s temperature measurement function.

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Three-Wire Device (Potentiometer) Tests

A potentiometer is a variable resistor. The signal generated is used by the vehicle computer to determine the
position and direction of movement of a device within the component. Typical potentiometer applications are:
Throttle Position Sensor (TPS), Exhaust Gas Recirculation Valve Position Sensor (EGR), and Vane Air Flow
Meter (VAF), etc.

An analog Throttle Position Sensor (TPS) is found on many vehicles. The TPS informs the vehicle computer of
the following:

• Throttle opening

• Whether and how fast the throttle is opening

• Whether and how fast the throttle is closing

• When the throttle is wide open

• When the throttle is at idle

One of its most important functions is to tell the computer that the throttle is opening. It replaces the
accelerator pump found on carbureted engines, stopping the engine from stumbling when the throttle is opened
quickly. When that happens, manifold absolute pressure (MAP) quickly rises (vacuum drops), causing vaporized
gasoline to condense on the manifold walls. Since there is less fuel available to the cylinders, more fuel must
be added to the air stream.

Another important function is to tell the computer that the throttle is closing. To maintain acceptable
emissions, the computer must lean out the mixture when MAP drops (vacuum rises).

For best fuel economy, the computer completely shuts off fuel in some engines when vacuum is high and the
throttle is at idle. Therefore, the computer must know when the throttle is at idle.

Throttle position information is a variable resistance from a potentiometer attached to the throttle shaft. Wide­open-throttle and throttle-closed signals come from switches attached to the TPS.

The TPS is really just a potentiometer or variable resistor. As you sweep the throttle, the resistance changes. As
its resistance changes, so does the voltage signal returning to the computer. The TPS can be tested either by
watching the voltage change or by watching the resistance change, using the bargraph on the meter.

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Potentiometer Resistance Change Test

Red

Black

Jumper
Wires

TPS
Connector

5V Supply

Ground

Signal

Meter setup to check resistance change:

• Set the rotary switch to resistance (Ω ) setting.

• If “ ” is present on the display, press the “DWL” button until “ ” disappears.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

• Press the “REC” button (selects the MAX.MIN.AVG function).

Disconnect the sensor connector and connect jumper wires between the connector and the sensor.

Connect:

• Black test probe to the ground circuit.

• Red test probe to the signal line (refer to the manufacturer’s schematic)

Rotate the TPS by moving the throttle and watch the bargraph move as the TPS turns. The resistance reading
should change as the signal arm on the TPS is moved (signal sweep).

As you rotate the TPS to change resistance, the bargraph moves smoothly if the TPS is good and moves
erratically if it is bad.

NOTE: Do not insert the test probe tips into the TPS as they may damage the smaller type plug on the TPS

connector.

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Potentiometer Voltage Change Test

Red

Black

Jumper
Wires

TPS
Connector

5V Supply

Ground

Signal

Meter setup to check voltage change:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

• Press the “REC” button (selects the MAX.MIN.AVG function).

Disconnect the sensor connector and connect jumper wires between the connector and the sensor.

Connect:

• Black test probe to the ground circuit.

• Red test probe to the signal line.

Turn the ignition key on; do not start the engine.

Rotate the TPS by moving the throttle and watch the bargraph move. The volatge drop should change as the
position of the signal arm on the TPS moves (signal sweep).

The bargraph should increase smoothly without jumping if the TPS is good.

Refer to the manufacturer’s specications. If the voltage change is not within the specications, check for
sources of excess resistance before replacing potentiometer: poor connectors, connections, or breaks in the
wiring.

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NOTE: Do not insert the test probe tips into the TPS as they may damage the smaller type plug on the TPS

connector.

Oxygen (O2) Sensor Test

The Oxygen (Lambda) Sensor samples the amount of oxygen (O2) in the exhaust stream. The O2 sensor produces
an output voltage that is a direct ratio to the oxygen level in the exhaust stream. The vehicle computer uses this
signal to change the air/fuel mixture ratio.

This test checks the signal output voltage levels of the O2 sensor.

O

2

Black

Red

Sensor

Signal Output
Voltage Wire

Good
Ground

Exhaust
Manifold

Meter setup to measure signal output voltage of the oxygen sensor:

• Set the rotary switch to voltage ( ) setting.

• Press the “DC/AC” button until “ ” appears on the display.

• Insert the black lead in the “COM” jack.

• Insert the red lead in the “ ” jack.

• Press the “REC” button (selects the MAX.MIN.AVG function).

Connect:

• Black test probe to a good quality ground.

• Red test probe to the signal output voltage wire.

NOTE: Be careful not to burn yourself on the hot exhaust manifold.

Run the engine at a fast idle (2,000 RPMs) for a few minutes. The O2 voltage readings should sweep between
100mV (lean) and 900mV (rich).

Once the O2 sensor reaches operating temperature, the DC voltage reading should begin to sweep. Under
varying operating conditions, the O2 voltage will rise and fall, but usually averages around 0.45V dc.

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Pressure Sensor Tests

Recommended electrical test procedures for pressure sensors such as Manifold Absolute Pressure (MAP)
and Barometric Pressure (BP) vary greatly depending upon type and manufacturer. Refer to the vehicle
manufacturer’s service manual for the schematics, specications, and test procedures.

Analog Type Pressure Sensor. Analog sensor can be tested using the voltage tests described for 3-wire
potentiometer. Use a vacuum pump to vary the pressure on the sensor in place of sweeping the sensor.

Digital Type Pressure Sensor. A digital sensor can be tested by using the frequency (Hz) function of the meter
with the same series of tests suggested for 3-wire potentiometer voltage tests. Use a vacuum pump to vary the
pressure on the sensor in place of sweeping the sensor.

In all cases, refer to the vehicle manufacturer’s service manual for the correct testing procedures.

NOTE: Resistance tests are impossible for pressure sensors because all pressure sensors have voltage or

frequency output.

Output Device (Actuator) Tests

The electrical tests for output devices varies depending upon type and manufacturer. Consult the vehicle
manufacturer’s service manual for the schematics, specications, and test procedures.

Primary output devices generate a form of electromagnetic ON/OFF signal, which will generally be one of the
following three signals:

• On or Off only (e.g., switches)

To check an on/off device such as a switch, perform continuity tests with the switch in the on and off
position.

• Pulse width (e.g., fuel injectors)

Pulse width is the length of time an output device (actuator) is energized. To check fuel injectors, measure
the On time using the pulse width measurement function.

• Duty cycle (e.g., mixture control solenoid)

Duty cycle (or duty factor) is the percentage of time a signal is above or below a trigger level during
one cycle. The amount of On time is measured as a percentage of the total On/Off cycle. To check a
mixture control solenoid, measure the percent of high (+) or low (-) time in a duty cycle. In most cases of
automotive electronics, the low (-) time is the On time.

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9. SUMMARY OF AUTOMOTIVE ELECTRICAL SYSTEM TESTS

Electrical System Tests

Automotive Systems

and Components

Measurement Type

Voltage

Presence

and Level

Voltage

Drop

Current (Amps)

Resistance

(Ohms)

Frequency (Hz)

Charging System

Alternators   
Connectors

  

Diodes

 

Regulators

 

Cooling System

Connectors   
Fan Motors

  

Relays

  

Temperature Switches

  

Ignition System

Coils  
Condensers

 

Connectors

  

Contact Set (points)

 

MAF Sensors

 

Magnetic Pickup

  

MAP/BP Sensors

 

O2 Sensors

 

Starting System

Batteries  
Connectors

 

Interlocks



Solenoids

  

Starters

  

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

Application Guide

Amps DC*

Analog Pointer

Continuity % DutyHZTemperature

Milliamps

Millivolts

REC

Ohms

ms-Pulse

RPM

HOLD

Volts AC

Volts DC

REL

DWELL

IGNITION/ENGINE

Coils

  

Computer Temp Sensors

    

Condensers (Capacitors)

    

Connectors

      

Contacts Set

      

Distributor Cap



Engine Speed



Feedback Carburetors

     

Fuel Injectors (Electronic)

      

Hall-Type Sensors

       

Idle Air Motors

        

Ignition Modules

   

MAF Sensor

  

Magnetic Pickups

       

MAP & BP Sensors

   

O2 Sensors

   

Throttle Position Sensors

    

STARTING SYSTEM

Battery

   

Connectors

     

Interlocks (neutral safety
switch)

   

Solenoids

      

Starters



     

COOLING SYSTEM

Connectors

     

Fan Motor

   

Radiator

 

Relays

    

Temperature Sensors

  

Temperature Switches

     

800.MACTOOLS

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Application Guide

Amps DC*

Analog Pointer

Continuity % DutyHZTemperature

Milliamps

Millivolts

REC

Ohms

ms-Pulse

RPM

HOLD

Volts AC

Volts DC

REL

DWELL

CHARGING SYSTEM

Alternators

      

Computerized Regulators

     

Connectors

    

Diodes, (AC Ripple)

  

Diode Rectier

  

Regulators

    

BODY ELECTRIC

Compressor Clutch

    

Lighting Circuits

  

Relay and Motor Diodes



Transmissions

  

* Used with a DC current probe

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10. SPECIFICATIONS

Except where specied specially, True-RMS responding accuracy is specied from 10 % to 100% of range;
Crest Factor: < 3 : 1

Accuracy specications take the form of:

±([% of Reading]+[number of Least Significant Digits])

DC Voltage

Range Resolution Accuracy

400mV 0.1mV

± (0.3% + 2)

4V 0.001V

40V 0.01V

400V 0.1V

1,000V 1V ± (0.75% + 3)

Input Impedance:

Ω

AC Voltage

Range Resolution

Accuracy

50Hz - 60Hz 45Hz - 1kHz

4V 0.001V

± (0.75% + 3)

± (2.5% + 5)

40V 0.01V
400V 0.1V
750V 1V ± (0.75% + 5)

Input Impedance: Ω
Display: True-RMS

About 10M

About 10M

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DC Current

Range Resolution Accuracy

400µA 0.1µA

± (0.5% + 1)

4,000µA 1µA

40mA 0.01mA

± (0.8% + 3)

400mA 0.1mA

4A 0.001A

± (1.5% + 5)

10A 0.01A

AC Current

Range Resolution Accuracy

400µA 0.1µA

± (0.8% + 1)

4,000µA 1µA

40mA 0.01mA

± (1.2% + 5)

400mA 0.1mA

4A 0.001A

± (2.0% + 5)

10A 0.01A

Display: True rms
Frequency Range: 45Hz - 1kHz

Resistance

Range Resolution Accuracy

400Ω 0.1Ω

± (0.5% + 10)

4kΩ 0.001kΩ

40kΩ 0.01kΩ

± (0.5% + 3)

400kΩ 0.1kΩ

4MΩ 0.001MΩ

± (1.5% + 10)

40MΩ 0.01MΩ

Open Circuit Voltage: < 3V dc

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Diode Test

Range Description Remark

2.000V

The approximate forward
voltage drop of the diode is
shown on the display.

Open Circuit Voltage: about 3V dc

Test Current: about 0.24mA

Continuity Test

Description Remark

The buzzer will sound when the resistance is less than about 40Ω.

The buzzer will not sound when the resistance is more than 150Ω.

The buzzer may or may not sound when the resistance is between
40Ω and 150Ω.

Open Circuit Voltage:
about 3V dc

Capacitance

Range Resolution Accuracy

1µF 0.001µF

± (2.0% + 5)

10µF 0.01µF

100µF 0.1µF ± (3.0% + 5)

1,000µF 1µF ± (5.0% + 5)

Note:

Accuracy is for capacitors that have negligible dielectric absorption.

Temperature

Range Resolution Accuracy

-40°C to 0°C 0.1°C ± (4.0°C + 3 digits)

0°C to 400°C 0.1°C ± (2% + 3°C)

1°C ± 3.0% of reading

-40°F to 0°F 0.1°F

0°F to 400°F 0.1°F ± (2% + 5.4°F)

400°F to 2,498°F 1°F

± (7.2°F + 3 digits)

Use K type thermocouple.

Note:

1. Accuracy does not include error of the thermocouple probe.

2. Accuracy specication assumes ambient temperature is stable to ±1°C. For ambient temperature changes
of ±5°C, rated accuracy applies after 1 hour.

± 3.0% of reading

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Frequency (Hi-Sen Hz)

Range Resolution Accuracy

200Hz 0.01Hz ± (0.05% + 2)

2,000Hz 0.1Hz

20kHz 0.001kHz

200kHz 0.01kHz

Minimum Frequency: 0.5Hz
Sensitivity: 250mV

RPM IP

Range Resolution Accuracy

30 - 9,000RPM 1RPM ± (0.5% + 2)

7 selectable trigger levels and ± trigger slopes

RPM IG

Range Resolution Accuracy

60 - 12,000RPM 1RPM ± (0.5% + 2)

7 selectable trigger levels and ± trigger slopes
9 Selectable Cylinder Numbers: 1, 2, 3, 4, 5, 6, 8, 10, 12

Duty Cycle

Range Resolution Accuracy

0.0% - 99.9% 0.1% ± (0.2%/kHz + 1)

Pulse Width: > 2µs
7 selectable trigger levels and ± trigger slopes

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Dwell Angle

Range

*1

Resolution Accuracy

0.0° - 356.4° °0.1 ± (1.2°/krpm + 2)

Pulse Width: > 2µs
7 selectable trigger levels and ± trigger slopes
9 Selectable Cylinder Numbers: 1, 2, 3, 4, 5, 6, 8, 10, 12
*1 Measurement range can vary with engine RPM and trigger slope.

Pulse Width

Range Accuracy

0.1ms - 1999.9ms ± (0.5% + 1)

Pulse Width: > 2µs
7 selectable trigger levels and ± trigger slopes

Frequency (Automotive Hz)

Range Resolution Accuracy

200Hz 0.01Hz

± (0.5% + 2)

2,000Hz 0.1Hz

Minimum Frequency: 0.5Hz
7 selectable trigger levels and ± trigger slopes

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11. GENERAL SPECIFICATIONS

Display (LCD):

Digital: Counts – 4,000 (frequency range: 20,000)

Updates – 1 time/sec in RPM, FREQ, Duty Cycle, Dwell, and Pulse Width;

3 times/sec in all other functions

Analog: 2×41 segments

Updates – 20 times/sec

Fuse Protection:

mA or µA: 1,000V/500mA FAST fuse, Min. Interrupt Rating 10,000A
A: 1,000V/10A FAST fuse, Min. Interrupt Rating 10,000A

IP Degree: IP20
Storage Temperature: -20°C to 60°C (-4°F to 140°F)
Operating temperature: 0°C to 45°C (32°F to 113°F)
Relative Humidity: 0% to 80% (0°C to 35°C; 32°F to 95°F)

0% to 70% (35°C to 45°C; 95°F to 113°F)

Temperature Coefficient: 0.15 × (specied accuracy)/°C (< 18°C or > 28°C; < 64°F

or > 82°F)

Battery: 9V battery, 6F22 or equivalent, 1 piece
Size: 209 × 117.5 × 70 mm
Weight: About 637g (including battery)

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12. MAINTENANCE

General Maintenance

Periodically wipe the case with a damp cloth and a little mild detergent. Do not use abrasives or solvents.

Use the following procedure to clean the terminals:

1. Set the rotary switch to OFF position and remove all test leads from the meter.

2. Shake out any dirt which may exist in the terminals.

3. Soak a new swab with alcohol.

4. Work the swab around in each terminal.

If you will not use the meter in a period of more than 60 days, remove the battery and store it separately.

Replacing Battery and Fuse

WARNING

TO AVOID ELECTRICAL SHOCK OR PERSONAL INJURY, REMOVE THE TEST LEADS AND ANY INPUT SIGNAL

BEFORE REPLACING BATTERY OR FUSE.

TO PREVENT DAMAGE OR INJURY, INSTALL ONLY FUSES WITH THE RATINGS SPECIFIED.

TO AVOID FALSE READINGS, WHICH COULD LEAD TO POSSIBLE ELECTRIC SHOCK OR PERSONAL INJURY,

REPLACE THE BATTERY AS SOON AS THE LOW BATTERY INDICATOR ( ) APPEARS.

To replace the battery:

1. Set the rotary switch to the “OFF” position and remove all test leads from the meter.

2. Remove the screw on the battery cover and remove the battery cover.

3. Replace the old battery with a new one of the same type.

4. Reinstall the battery cover and the screw.

To replace the fuse:

1. Set the rotary switch to the “OFF” position and remove all test leads from the meter.

2. Remove the screw on the battery cover and remove the battery cover.

3. Remove the screws on the back cover and move the back cover aside gently.

4. Replace the blown fuse with a new one of the same ratings.

5. Reinstall the back cover and its screws. Then reinstall the battery cover and its screw.

This meter uses two fuses:

F1: 1,000V/500mA FAST fuse, Ø6.35X32mm, Min. Interrupt Rating 10,000A
F2: 1,000V/10A FAST fuse, Ø10X38mm, Min. Interrupt Rating 10,000A

800.MACTOOLS

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13. METER-PC COMMUNICATION SOFTWARE INSTRUCTION

Place the supplied CD on the tray of the CD-ROM drive of your PC and close it. Locate the “EM721.exe” le in
the “EM721-PC” folder on the CD, and double-click this le to run this communication software. Connect the
supplied USB data line to the USB port on the top of the meter, and connect the other end of this USB data
line to a USB port on your PC. Turn on the meter. Then press and hold down the “REL” button on the meter
for about 1 second to turn on the USB communication function; “ ” will appear on the meter screen as an
indication. (NOTE: After you nish using the USB communication function, turn off this function to save battery
power by pressing and holding down this “REL” button for about 1 second.)

Run the communication software, the following EM721-PC interface will appear:

Readings transferred from the

meter will appear here.

Buttons

Click the “COMSETTING” button, the Serial-Port Debug Assistant interface will appear.

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78

On the serial port drop-down list box on the Serial-Port Debug Assistant interface, select the PC serial port
which is being used by the meter. Then click the “Open” button on this interface, the “Open” button will change
into “Close” button.

Hexadecimal Codes

hexadecimal code display area

Serial port drop-down list box

" Open " Button

Serial-Port Debug Assistant interface

“COMSETTING” button

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When a series of hexadecimal codes appear on the blank area of the Serial-Port Debug Assistant interface, the
display area on the upper left area of the M721-PC interface will show readings of the meter in almost a
realtime mode. Close the Serial-Port Debug Assistant interface by clicking the “

” button at the top right

corner of the Serial-Port Debug Assistant interface. Now the meter has been successfully connected to the PC.
(Clicking the “Close” button on the Serial-Port Debug Assistant interface will stop the data transfer from the
meter to the PC.)

The eight buttons on the left half of the EM721-PC interface correspond to the buttons on the meter,
respectively. You can use these buttons of the interface in the same way you use the buttons on the meter, but
the “REL” button on the interface can not be used to turn on or off the USB communication function of the
meter. To turn on or off the USB communication function of the meter, press and hold down the “REL” button
on the meter for 1 sec. In addition, the rotary switch on the left half of the interface is not functional and can
not be used.

This rotary switch is not functional. Readings transferred from the meter

appear in the table here.

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80

61 45

7

2 3

Explanations:

1. END/START Button - - - Used to stop/start transferring data.

2. COMSETTING Button - - - Used to display the Serial-Port Debug Assistant interface

3. “MIN” Box - - - Automatically shows the minimum reading of all readings being listed in the table on the

“Data Logging” tab.

4. “MAX” Box - - - Automatically shows the maximum reading of all readings being listed in the table on the

“Data Logging” tab.

5. “AVG” Box - - - Automatically shows the average reading of all readings being listed in the table on the

“Data Logging” tab.

6. “Data Logging” Tab - - - Used to display transferred data in table.

“Clear” Button - - - Used to clear all the data being listed in the table on the “Data Logging” tab.
“Save” Button - - - Used to save the data being listed in the table on the “Data Logging” tab as a le.
“Data Len” Spin Edit Box - - - Used to set the max. number of records that can be displayed in the table on

the “Data Logging” tab.

7. “Draw Graph” Tab - - - Used to show the plot of the readings being listed in the table on the “Data

Logging”tab.

“unit” Drop-down List Box - - - Used to select a desired unit for the Y-axis.

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NOTE

1. This manual is subject to change without notice.

2. Our company will not take the other responsibilities for any loss.

3. The contents of this manual can not be used as the reason to use the meter for any special application.

DISPOSAL OF THIS ARTICLE

Dear Customer,
If you at some point intend to dispose of this article, then please keep in
mind that many of its components consist of valuable materials, which
can be recycled.

Please do not discharge it in the garbage bin, but checkwith your local
council for recycling facilities in your area.

82

Manual EM721

CUSTOMER SERVICE

We at Mac Tools are committed to our customers, please reference the following phone number for a direct
contact to one of our customer technicians. They will be more than happy to help with any service or warranty
questions you may have about your digital multimeter.

Mac Tools

505 North Cleveland Avenue

Suite 200

Westerville, Ohio 43082

800.MACTOOLS

MACTOOLS.COM

EM721 Digital Multimeter

Para reducir el riesgo de lesiones, lea y
comprenda estas advertencias e instrucciones
de seguridad antes de usar la herramienta.
Conserve estas instrucciones junto con la
herramienta para consulta en el futuro. Si
tienealguna pregunta, póngase en contacto con
su representante o distribuidor de MAC TOOLS.

ADVERTENCIA

Multímetro automotor

Manual del usuario

EM721

MACTOOLS.COM

84

GARANTÍA

Se garantiza que este instrumento está libre de defectos en materiales y mano de obra durante un período
deun año. Nuestra obligación ante el comprador original se limitará a la reparación o el reemplazo, a nuestro
costo (sin incluir los gastos de envío), de una herramienta defectuosa, si dicho comprador original la devuelve
en el plazo de un año desde la fecha de compra, con todos los gastos de envío prepagados. ESTA GARANTÍA
NO CUBRE LOS DEFECTOS O LOS DAÑOS A LA HERRAMIENTA (i) después de que termina el período
degarantía; (ii) que resulten del uso indebido o fuera de lo común; (iii) que resulten de un mantenimiento o
unuso inadecuado de la herramienta; o (iv) que resulten de cualquier reparación o servicio de mantenimiento
realizados por terceros que no sean Mac Tools. Esta garantía no cubre los elementos expansibles como baterías
y/o fusibles.

LIMITACIÓN DE LA RESPONSABILIDAD

Este manual explica cómo utilizar el medidor para realizar pruebas de diagnóstico y encontrar posibles lugares
de problemas electrónicos de automóviles. No le indica cómo corregir el problema. Una vez que haya localizado
un problema, consulte el manual de servicio de su automóvil u otros manuales que suministren información
especíca necesaria para la reparación.

Toda la información, ilustraciones, especicaciones contenidas en este manual se basan en la información
más reciente disponible al momento de publicación. Se reserva el derecho de realizar cambios en cualquier
momento sin previo aviso.

ÍNDICE

1. Información de seguridad .................................................................. 86

2. Introducción .................................................................................... 89

3. Panel frontal .................................................................................... 90

4. Comprensión de la pantalla ............................................................... 96

5. Pruebas eléctricas y mediciones básicas ............................................ 99

6. Mediciones automotrices básicas ..................................................... 108

7. Pruebas básicas de diagnóstico automotor ........................................ 115

8. Pruebas básicas de componentes automotores .................................. 140

9. Resumen de las pruebas del sistema eléctrico automotor ................... 149

10. Especicaciones ............................................................................. 152

11. Especicaciones generales ............................................................. 157

12. Mantenimiento ............................................................................... 158

13. Instrucciones del software de comunicación entre medidor y PC ......... 159

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DESCRIPCIÓN GENERAL DEL MEDIDOR

Límites de mediciones:

Tensión de CC 0.1 mV a 1000 V

Tensión de CA 0.001 V a 750 V

RPM IP 30 a 9000 RPM

RPM IG 60 a 12000 RPM

CC (Amperios) 0.1 µA a 10 A

CA (Amperios) 0.1 µA a 10 A

Resistencia (Ohmios) 0.1 a 40 MΩ

Frecuencia (Hz) 0.5 Hz a 200 kHz

% de ciclo de trabajo 0 a 99.9 %

Permanencia (Grados) 0° a 356.4°

Ancho de pulso (Milisegundos) 0.1 ms a 1999.9 ms

Temperatura (Celsius/Fahrenheit) - 40°C a +1370 °C (- 40°F a +2498°F)

Capacitancia (Microfaradios) 0.001 µF a 999 µF

Comprobación de continuidad Alarma sonora a aprox. < 40 Ω en el rango de 400 Ω

MACTOOLS.COM

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1. INFORMACIÓN DE SEGURIDAD

Este medidor se ha diseñado de acuerdo con la norma IEC 61010 en relación con instrumentos de medición
electrónicos con una categoría de medición (CAT III 1000V) y grado de contaminación 2.

ADVERTENCIA

SIGA ESTOS LINEAMIENTOS PARA EVITAR POSIBLES LESIONES O DESCARGAS ELÉCTRICAS:

• No use el medidor si está dañado. Antes de usar el medidor, revise la carcasa.

Preste especial atención al aislamiento que rodea los conectores.

• Revise los cables de prueba para vericar que no haya daños en el aislamiento ni metal expuesto.

Compruebe los cables de prueba para determinar su continuidad. Reemplace los cables de prueba
dañados antes de usar el medidor.

• No use el medidor si no funciona con normalidad. La protección puede estar dañada. En caso de duda,

repare el medidor.

• No haga funcionar el medidor si hay gas, vapor o polvo explosivos (o inamables).

• No supere la tensión nominal, según lo indicado en el medidor, entre los terminales o entre cualquiera

deellos y la conexión a tierra.

• Antes de su uso, verique el funcionamiento del medidor mediante la medición de una tensión conocida.

• Cuando realice la reparación del medidor, utilice solamente piezas de repuesto especicadas.

• Tome precauciones al trabajar con tensiones superiores a 30 VCA RMS, máximo de 42 V o 60 VCC.

• Estas tensiones representan un peligro de descarga eléctrica.

• Cuando se utilizan las sondas, mantenga los dedos detrás de los protectores correspondientes en dichas sondas.

• Al realizar las conexiones, conecte el cable de prueba común antes de conectar el cable de prueba vivo.

• Cuando desconecte los cables de prueba, desconecte primero el cable de prueba vivo.

• Quite los cables de prueba del medidor antes de abrir la cubierta de la batería o la carcasa.

• No haga funcionar el medidor con la cubierta de la batería o partes de la carcasa extraídas o ojas.

• Para evitar falsas lecturas, que podrían producir descargas eléctricas o lesiones personales, reemplace

labatería en cuanto aparezca el indicador de batería baja ( ).

• No use el medidor de un modo que no esté especicado en este manual. De lo contrario, las funciones

deseguridad provistas por el medidor pueden verse afectadas.

• Cuando mida corriente utilizando los cables de prueba, desconecte la alimentación al circuito antes

deconectar el medidor al circuito. Recuerde colocar el medidor en serie con el circuito.

• Para evitar descargas eléctricas, no toque ningún conductor sin aislamiento con la mano o la piel,

y no se ponga a tierra usted mismo mientras esté utilizando el medidor.

• Cumpla con los códigos de seguridad locales y nacionales. Debe usarse equipo de protección individual

para evitar descargas eléctricas y lesiones por ráfaga de arco en los casos en que los conductores vivos
estén expuestos.

• Siga los requisitos correspondientes y el procedimiento de seguridad especicado en el Manual del usuario

y en el Manual de servicio provisto por el fabricante del vehículo bajo prueba.

• El gas de escape contiene monóxido de carbono que es inodoro, genera tiempos de reacción más lentos

y puede provocar lesiones graves. Cuando realice la prueba del vehículo con el motor en funcionamiento,
dicha prueba siempre debe realizarse en un área bien ventilada o con el venteo del gas de escape hacia
elexterior del edicio.

• Aplique el freno de estacionamiento y trabe las ruedas antes de probar o reparar el vehículo, a menos

quese indique lo contrario. Es especialmente importante bloquear las ruedas de los vehículos con
traccióndelantera: el freno de estacionamiento no sujeta las ruedas motrices. El sistema de combustible
ode encendido debe estar desactivado para realizar pruebas del sistema de arranque.

• Use siempre gafas de seguridad cuando trabaje cerca de baterías.

• No fume ni permita la presencia de llamas abiertas o chispas en el área de trabajo. Los humos de la

gasolina y los gases producidos por la batería son muy explosivos.
Mantenga cigarrillos, chispas y llamas abiertas alejados de las baterías en todo momento.

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• Para evitar lesiones personales, no toque ningún objeto en movimiento o caliente. Mantenga alejado

elcuerpo y la ropa de piezas del motor en movimiento o calientes en todo momento.

• Especialmente en aplicaciones marinas con motores internos o internos/fuera de borda, asegúrese de

queel área de trabajo esté bien ventilada. Haga funcionar el achique por lo menos cuatro minutos antes
dearrancar el motor o hacer conexiones de los cables de prueba.

• Siempre evite trabajar solo.

• No use el medidor si este o su mano están húmedos.

• Peligro restante: Cuando un terminal de entrada se conecta a un potencial vivo peligroso, se debe tener

encuenta que este potencial puede tener lugar en todos los demás terminales.

• CAT III: La categoría de medición III es para las mediciones realizadas en instalaciones edilicias. Ejemplos

deesta categoría son mediciones en tableros de distribución, disyuntores, cableado, incluidos cables, barras
de distribución, cajas de empalme, interruptores, enchufes-tomacorrientes en la instalación ja y equipos
para uso industrial y algunos otros equipos, por ejemplo, motores estacionarios con conexión permanente
a la instalación ja. No use el medidor para mediciones dentro de las categorías de medición IV.

PRECAUCIÓN

PARA EVITAR POSIBLES DAÑOS AL MEDIDOR O AL EQUIPO BAJO PRUEBA, SIGA ESTOS LINEAMIENTOS:

• Desconecte la alimentación del circuito y descargue todos los condensadores antes de probar la resistencia,

los diodos, los condensadores, la temperatura y la continuidad.

• Utilice los terminales adecuados en cuanto a función y rango para sus mediciones.

• Antes de medir la corriente, compruebe los fusibles del medidor y desconecte la alimentación al circuito

antes de conectar el medidor a dicho circuito.

• Antes de girar el interruptor giratorio para cambiar de función, desconecte los cables de prueba del circuito

bajo prueba.

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Símbolos

Corriente alterna

Corriente continua

Corriente continua y alterna

Precaución, riesgo de peligro, consulte el manual de operación antes de usar.

Precaución, riesgo de descarga eléctrica.

Terminal de puesta a tierra

Fusible

Cumple con las directivas de la Unión Europea

El equipo se encuentra completamente protegido con aislamiento doble o aislamiento reforzado.

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2. INTRODUCCIÓN

El medidor es un multímetro automotor portátil y alimentado a batería. Es una herramienta de gran utilidad.

Este manual del usuario le indica cómo utilizar el medidor. También puede necesitar un manual que
proporcione información técnica sobre el vehículo que planea probar. Los recursos de información más
importantes son los manuales de servicio de reparación del vehículo que, por lo general, pueden comprarse
a través de concesionarios automotores. También están disponibles a través de una serie de editores que se
especializan en el suministro de manuales de información técnica a talleres de reparación independientes.

Este manual del usuario puede emplearse como guía para que comience con el procedimiento de resolución de
problemas. Su aprendizaje real puede lograrse de mejor modo mediante la experiencia. A medida que se torne
más hábil en el uso de este multímetro automotor para la resolución de problemas, muy pronto aprenderá a
detectar cómo determinados síntomas eléctricos se relacionan con diversos problemas de capacidad de manejo.

Características del medidor

• Mediciones precisas de frecuencia y pulso con 20,000 recuentos en la pantalla de alta resolución de

4000recuentos.

• El gráco de barras analógico de alta velocidad de 41 segmentos se actualiza 20 veces/s, lo que ofrece

unaprecisión casi perfecta en tiempo real.

• Prueba precisa de circuitos electrónicos automotores y mediciones avanzadas expresadas en voltios

de CC/CA, amperios de CC/CA, resistencia, etc.

• Lectura directa de la permanencia sin usar la tabla de conversión del ciclo de trabajo a la permanencia

alprobar la inyección electrónica de combustible, los carburadores de retroalimentación y los sistemas
deencendido

• Medición de RPM para motores de automóviles con 1 a 12 cilindros, usando los cables de prueba o el

captador inductivo

• Función de ms-ancho de pulso para la prueba de inyectores de combustible en tipos de PFI (Inyector de

combustible en puerto) y TBI (Inyector de cuerpo del acelerador)

• Para mediciones precisas de RPM, permanencia, ciclo de trabajo y ms-ancho de pulso de los inyectores,

elmedidor dispone de siete activaciones +/- de siete pasos regulables en 1 a 12 cilindros, de 2 o 4 tiempos
para motores fuera de borda, motocicletas y motores convencionales

• Medición de temperatura de hasta 2,498°F (1,370°C) para catalizadores, interruptor de ventilador, etc.

• Medición de capacitancia y frecuencia no automotriz

• Pantalla con retroiluminación

• Comunicación mediante USB

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3. PANEL FRONTAL

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1. Pantalla digital

Las lecturas digitales se muestran en una pantalla de 4,000 recuentos con indicación de polaridad
yla colocación automática del punto decimal. Cuando el medidor está activado, todos los segmentos
ysímbolos de la pantalla aparecen brevemente durante una prueba automática.

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2. Gráfico de barras analógico

El gráco de barras analógico ofrece una representación analógica de las lecturas y se actualiza 20 veces
por segundo. El gráco de barras de 2 × 41 segmentos se ilumina de izquierda a derecha a medida que
aumenta la entrada. El gráco de barras es más fácil de leer cuando los datos generan que la pantalla
digital cambie rápidamente. También es útil para establecer tendencias o datos direccionales. Las barras
también indican el nivel de activación.

3. Botón “±TRIG” (Activación ±)

Este botón “± TRIG” (Activación ±) puede utilizarse para alternar entre la pendiente de activación negativa
(-) y positiva (+) y regular el nivel de activación.

Cuando el medidor está en la función de medición de RPM, ciclo de trabajo, ancho de pulso, frecuencia
(Hz automotriz) o de permanencia, mantenga presionado el botón “± TRIG” (Activación ±) durante
1segundo para alternar entre la pendiente de activación negativa (-) y positiva (+). La pendiente está
indicada por el signo + o - al lado de “TRIG” (Activación ±) en la esquina inferior izquierda de la pantalla.
El medidor elige por conguración predeterminada la pendiente de activación negativa (-). Una vez que la
pendiente de activación esté seleccionada, presione el botón “± TRIG” (Activación ±) repetidamente para
ajustar el nivel de activación si la lectura del medidor es demasiado alta o inestable.

El ajuste del nivel de activación tiene siete pasos. Presione el botón “± TRIG” (Activación ±) para moverse
un paso a la vez para seleccionar un nivel de activación adecuado.

PASO DE ACTIVACIÓN

Nivel de tensión

(RPM, ciclo de trabajo, ms,

Hz[automotriz], permanencia)

Nivel de activación aproximado tal como

lo indica el gráfico de barras

+4 +8.2 V

+3 +6.8 V

+2 +3.2 V

+1 +1.4 V

-1 -1.4 V

-2 -3.2 V

-3 -6.8 V

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4. Botón “REL” (Relativo)

Se utiliza para ingresar o salir del modo Relativo así como para activar o desactivar la función de
comunicación mediante USB.

Presione este botón “REL” para ingresar en modo Relativo. El medidor almacena la lectura actual como
referencia para las mediciones posteriores. Aparece “ ” como un indicador del modo Relativo, y la
pantalla indica cero.

En modo Relativo, cuando realice una nueva medición, la pantalla muestra la diferencia entre la referencia
y la medición nueva.

Para salir del modo Relativo, simplemente presione el botón “REL” (Relativo) nuevamente. “ ” desaparece.

Nota:

•

El medidor ingresa en el modo de rango manual cuando entra en el modo Relativo.

• Cuando se utiliza el modo Relativo, el valor real del objeto bajo prueba no debe exceder la lectura

de rango completo del rango seleccionado. Use un rango de medición más alto, si es necesario.

• El modo Relativo no está disponible en las funciones de prueba de diodos y de continuidad.

Mantenga presionado este botón “REL” (Relativo) durante 1 segundo para activar la función de
comunicación mediante USB, aparecerá “ ” en la pantalla como una indicación. Para desactivar
la función de comunicación mediante USB, mantenga presionado este botón “REL” (Relativo) durante
1segundo nuevamente. “ ” desaparece.

5. Botón “DWL” (Permanencia)

Este botón “DWL” (Permanencia) se puede utilizar para seleccionar la función de medición de permanencia
o alternar entre las funciones de prueba de resistencia y continuidad.

Cuando el medidor está en la función RPM IG, puede presionar el botón “DWL” (Permanencia) para seleccionar
el modo de medición de permanencia; aparecerá “DWL” (Permanencia) en la pantalla como una indicación.
Lapermanencia es el número de grados de rotación del distribuidor donde los puntos permanecen cerrados.
La permanencia se puede medir para 1 a 12 cilindros. La conversión entre el ciclo de trabajo y la permanencia
puede obtenerse mediante la siguiente fórmula:

% de ciclo de trabajo =

Permanencia (en grados) × Cant. de cilindros × 100 %

360 grados

Permanencia =

360 grados

×

% de ciclo de trabajo

Cantidad de cilindros 100 %

Cuando el medidor está en la función de permanencia, puede presionar el botón “DWL” (Permanencia)
nuevamente o el “% DUTY” (% de trabajo) para volver a la función en la cual estaba el medidor justo antes
de ingresar en la función de permanencia.

Cuando el interruptor giratorio esté en la posición “Ω ”, presione el botón “DWL” (Permanencia) para
cambiar entre las funciones de prueba de resistencia y continuidad. Se puede utilizar una prueba de
continuidad para vericar que existe un circuito cerrado. La función de continuidad detecta cortocircuitos
ycircuitos abiertos que duran tan solo 100 milisegundos. En el rango de 400 Ω, la resistencia de menos
de40 Ω genera que suene la alarma sonora incorporada. Esta puede ser una valiosa ayuda para la resolución
de problemas cuando se buscan fallas intermitentes asociadas con conexiones, cables, relés, interruptores, etc.

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6. Botón “DC/AC” (CC/CA)

Se usa para conmutar entre la función de CC y CA o entre °C y °F.

Cuando el interruptor giratorio se encuentra en la posición “ ”, “10 ”, “m ” o “µ ”, puede presionar este
botón “DC/AC” (CC/CA) para cambiar entre la función de CA y CC; cuando la función CA está activada,
aparecerá “ ” en la pantalla como una indicación; cuando está activada la función CC, aparecerá “ ” en
la pantalla.

Presione el botón “DC/AC” (CC/CA) para cambiar entre °C y °F cuando el interruptor giratorio esté en la
posición “TEMP” (Temperatura). Cuando se selecciona la medición de temperatura en grados Celsius,
aparecerá “°C” en la pantalla como una indicación; y cuando se selecciona la medición de temperatura en
grados Fahrenheit, aparecerá “°F” en la pantalla como una indicación.

7. Interruptor giratorio

Las siguientes funciones se seleccionan mediante la conguración del interruptor giratorio en una posición
correspondiente:

Posición del

interruptor

Función

Voltios de CC/CA

m

Milivoltios de CC solamente

Ω

Prueba de resistencia/continuidad (ohmios)
Prueba de diodos

Capacitancia (Microfaradios)

TEMP Temperatura (Fahrenheit y Celsius)

Medición de frecuencia (frecuencia no automotriz) (Hercios)

Medición de RPM en motores de 2 o 4 tiempos con el captador inductivo en un
cable de la bujía.

Medición de RPM en motores de 1 a 12 cilindros con los cables de prueba en el
lado principal de la bobina de encendido y medición de ciclo de trabajo, ancho
de pulso, Hz (automotriz) y permanencia.

10

Corriente (Amperios) CC/CA

m

Corriente (Miliamperios) CC/CA

µ

Corriente (Microamperios) CC/CA

OFF Apaga el medidor

8. Terminal “ ”

Terminal de entrada para las mediciones de tensión, resistencia, continuidad, RPM, diodos, frecuencia,
capacitancia, temperatura, ciclo de trabajo, ancho de pulso y permanencia.

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9. Terminal “COM” (Común)

Terminal común (retorno) para todas las mediciones.

10. Terminal “mA μA”

Terminal de entrada para mediciones de corriente < 400 mA.

11. Terminal “A”

Terminal de entrada para mediciones de corriente entre 400 mA y 10 A.

12. Botón “RANGE” (Rango)

Este botón “RANGE” (Rango) puede utilizarse para:

• Alternar entre el modo manual y el modo de rango automático así como para seleccionar el rango

manual deseado.

• Seleccione el número de cilindros (1, 2, 3, 4, 5, 6, 8, 10 o 12) que se corresponda con el motor

cuando el medidor está en función de permanencia o RPM IG.

• Alternar entre motor de 2 tiempos (o motor de 4 tiempos con sistema de encendido sin distribuidor)

ymotor de 4 tiempos cuando el medidor está en la función RPM IP.

En una función que tiene el modo de rango manual y el modo de rango automático, el medidor elige de
forma predeterminada el modo de rango automático y aparece “ ” en la pantalla como una indicación.
Presione el botón “RANGE” (Rango) para ingresar al modo de rango manual, desaparecerá “ ” y el
medidor permanecerá en el rango actual.

En el modo de rango manual, puede presionar el botón “RANGE” (Rango) para seleccionar el rango más
elevado siguiente. En el rango más alto, el medidor se ajusta al rango más bajo. Para salir de modo manual
yvolver al modo de rango automático, mantenga presionado el botón de “RANGE” (Rango) durante 1segundo;
aparecerá “ ” en la pantalla como una indicación.

Seleccione siempre un rango superior al que espera que se encuentre la corriente o tensión. Luego, seleccione
unrango inferior si necesita una mayor precisión. Si el rango es demasiado alto, las lecturas son menos precisas.
Si el rango es demasiado bajo, el medidor muestra “OFL” (Sobrecarga) como una indicación de sobrecarga.

Cuando el medidor está en la función de RPM IG o de permanencia, presione el botón “RANGE” (Rango)
para alternar entre 1, 2, 3, 4, 5, 6, 8, 10 o 12 cilindros. El número de cilindros seleccionado se indica
mediante el número que precede al texto CYL (Ciclo) en la pantalla.

Cuando el medidor está en la función RPM IP, presione el botón “RANGE” (Rango) para alternar entre motor
de 2 tiempos (o motor de 4 tiempos con sistema de encendido sin distribuidor) y motor de 4 tiempos; el
número seleccionado de tiempos (o carreras) lo indica el símbolo (“ ” o “ ”).

13. Botón “% DUTY” (% de trabajo)

Cuando el medidor está en la función RPM IG, presione este botón “% DUTY” (% de trabajo) para medir el
ciclo de trabajo (o factor de trabajo) en porcentaje; aparece una lectura en %. Ciclo de trabajo es el porcentaje
del tiempo en el cual una señal está por encima o por debajo del nivel de activación durante un ciclo.

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Para seleccionar la función de ancho de pulso, presione el botón “% DUTY” (% de trabajo) nuevamente;
aparece una lectura en ms. El ancho de pulso es el tiempo durante el cual un actuador está activado.
Por ejemplo, los inyectores de combustible se activan mediante un pulso electrónico desde el módulo de
control del motor. Este pulso genera un campo magnético que hace que se abra la válvula de la boquilla
del inyector. El pulso naliza y la boquilla del inyector se cierra. Este tiempo de abierto a cerrado es el
ancho de pulso y se mide en milisegundos (ms)

Para seleccionar la función de frecuencia, presione el botón “% DUTY” (% de trabajo) de nuevo; aparece
una lectura en Hz. La frecuencia es la cantidad de ciclos que una señal completa cada segundo.

Puede pasar a través de RPM, ciclo de trabajo, ancho de pulso y frecuencia presionando este botón
“% DUTY” (% de trabajo).

Cuando el interruptor giratorio se encuentre en la posición “RPM IG”, puede presionar el botón “DWL”
(Permanencia) para seleccionar la función de medición de permanencia; aparecerá “DWL” (Permanencia)
en la pantalla como una indicación de dicha función.

Cuando se encuentre en la función de medición de permanencia, puede presionar el botón “DWL”
(Permanencia) nuevamente o “% DUTY” (% de trabajo) para regresar a la función anterior desde la cual
el medidor ingresó en la función de medición de permanencia.

14. Botón “HOLD” (Bloqueo)

Se utiliza para ingresar o salir del modo de Bloqueo así como para encender o apagar la retroiluminación.

Presione este botón “HOLD” (Bloqueo) para ingresar al modo de Bloqueo. Aparece “ ” en la pantalla como
una indicación y el medidor retiene la lectura actual en la pantalla. En el modo de Bloqueo, cuando el
medidor detecta una lectura estable nueva, emite una alarma sonora y muestra la nueva lectura estable.
Para salir del modo de Bloqueo, presione el botón “HOLD” (Bloqueo) nuevamente. “ ” desaparece.

Nota: Cuando el medidor está en el modo de Registro o Relativo, la función de Bloqueo simplemente

congela la lectura actual no actualizará la pantalla con la nueva lectura estable.

Para encender o apagar la retroiluminación, mantenga presionado este botón “HOLD” (Bloqueo) durante
1segundo.

15. Botón “REC” (Registro)

Presione el botón “REC” (Registro) para ingresar el modo de Registro, aparecerá “ ” en la pantalla como
una indicación. (El medidor saldrá del modo rango automático y permanecerá en el rango actual cuando
ingresa en modo de Registro). Esta función le permite registrar como el valor máximo, mínimo y promedio
de una serie de mediciones en la misma función y rango. Esta medidor emite una alarma sonora cada vez
que se registra un valor máximo o mínimo nuevo. Presione el botón “REC” (Registro) para desplazarse a
través de los valores máximo, mínimo y promedio. Cuando se captura una sobrecarga, se emite una alarma
sonora y el medidor muestra “OFL” como una indicación de sobrecarga. El medidor solo puede registrar
durante 24 horas en este modo.

Nota: El modo de Registro no está disponible en la función de diodos y continuidad.

16. Puerto USB

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Apagado automático

Cuando el interruptor giratorio se encuentre en la posición , el medidor se apagará automáticamente si no lo
opera durante 30 minutos (1 hora en el modo de Registro) mientras que la tensión de entrada sea inferior a 1 V.

Cuando el interruptor giratorio se encuentre en otra posición, el medidor se apagará automáticamente si no lo
opera durante 30 minutos (1 hora en el modo de Registro).

Aproximadamente 30 segundos antes de que el medidor se apague automáticamente, el símbolo “ ” se
encenderá parpadeando para recordarle que el medidor se apagará.

Para encender el medidor nuevamente, coloque el interruptor giratorio en la posición OFF (Apagado) primero y,
luego, en la posición deseada.

Para desactivar la función de apagado automático, encienda el medidor mientras mantiene presionado el botón
“HOLD” (Bloqueo).

Con el captador inductivo

El medidor se comercializa con un captador inductivo. El captador inductivo toma el campo magnético
generado por la corriente en el cable de la bujía y lo convierte en un pulso que activa la medición de RPM
porparte del medidor.

4. COMPRENSIÓN DE LA PANTALLA

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1. . Aparece cuando se ha seleccionado el modo RPM IG. En este modo, se pueden medir las
revoluciones por minuto en motores de 1 a 12 cilindros usando los cables de prueba en el lado principal
de la bobina de encendido.

2. . Aparece cuando se ha seleccionado el modo RPM IP. En este modo, se pueden medir las
revoluciones por minuto en motores de 2 o 4 tiempos con el captador inductivo en un cable de la bujía.

3. . Aparece cuando se selecciona el modo de permanencia.

4. . Aparece cuando se selecciona el modo de ciclo de trabajo.

5. 18 . Aparece cuando un determinado número de cilindros se selecciona en el modo de permanencia
oRPM IG. Presione el botón “RANGE” (Rango) para alternar entre motores de 1, 2, 3, 4, 5, 6, 8, 10 o
12cilindros.

6. . Aparece cuando se ha seleccionado 4 tiempos en el modo RPM IP. Presione el botón “RANGE”
(Rango) para alternar entre motores de 2 y 4 tiempos.

7. . Aparece cuando se ha seleccionado 2 tiempos en el modo RPM IP. Presione el botón “RANGE”
(Rango) para alternar entre motores de 2 y 4 tiempos.

8. . Indica que el valor que se muestra es el promedio de todas las lecturas realizadas desde que se
ingresó en el modo de Registro.

9. . Aparece cuando se selecciona la prueba de diodos.

10. . Aparece cuando se activa el modo Relativo.

11. . Aparece cuando se activa el modo de Registro.

12. . Aparece cuando se selecciona la prueba de continuidad.

13. . Aparece cuando el modo de Bloqueo está activo.

14. . Aparece cuando el nivel de la batería es bajo.

ADVERTENCIA

PARA EVITAR FALSAS LECTURAS, QUE PODRÍAN PRODUCIR DESCARGAS ELÉCTRICAS O LESIONES

PERSONALES, REEMPLACE LA BATERÍA EN CUANTO APAREZCA ESTE INDICADOR DE BATERÍA BAJA.

15. . Indica que el valor que se muestra es la lectura máxima realizada desde que se ingresó en el modo
de Registro.

16. . Aparece cuando se activa el modo de rango automático.

17. . Indica que el valor que se muestra es la lectura mínima realizada desde que se ingresó en el modo
deRegistro.

18. . Aparece cuando se selecciona la función de medición de CC.

19. . Aparece cuando se selecciona la función de medición de CA.

20. . Indica lecturas negativas. En modo Relativo, este signo indica que la entrada actual es inferior a la
referencia almacenada.

21. . Indica que la función de apagado automático se ha activado.

22. . Indica que se ha activado la función de comunicación mediante USB.

23. . Aparece cuando se selecciona una pendiente de activación - o + mientras el medidor se encuentra
en el modo RPM IP o RPM IG (ciclo de trabajo, ancho de pulso, permanencia o Hz). El medidor elige por
conguración predeterminada una pendiente de activación - (negativa). Presione el botón “± TRIG”
(Activación ±) durante 1 segundo para cambiar entre la pendiente de activación positiva (+) y negativa (-).
También aparece cuando el gráco de barras indica el nivel de activación.

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24. . Indica la polaridad de la entrada.
También indica una pendiente de activación - (negativa) o + (positiva) cuando se ha seleccionado una pendiente.

TIEMPO ALTO

TIEMPO BAJO

1 CICLO DE TRABAJO

Seleccione una pendiente de activación negativa (-) para medir el tiempo bajo (-) y una pendiente de
activación positiva (+) para medir el tiempo alto (+). Por ejemplo, cuando se realiza la medición del ciclo
de trabajo del solenoide de control de mezcla, el tiempo (-) bajo es el tiempo de encendido, en la mayoría
de los casos.

25. ESCALA DE VISUALIZACIÓN ANALÓGICA. Se muestra con indicadores analógicos de 41 posiciones.

26. Los siguientes símbolos indican la unidad de valor visualizado:

DWL° El número de grados de rotación del distribuidor donde los puntos permanecerán

cerrados, medido para 1 a 12 cilindros

% Porcentaje, se utiliza para la medición del ciclo de trabajo

°C/°F Medición de la temperatura en grados Fahrenheit o centígrados

Ω Ohmios

kΩ Kiloohmio (1 × 10 ohmios)

Megaohmio (1 × 10 ohmios)

Hercios (1 ciclo/s)

Kilohercio (1 × 10 ciclos/s)

Voltios

Milivoltios (1 × 10 voltios)

Amperios (A)

Miliamperios (1 × 10 A)

Microamperios (1 × 10 A)

Microfaradios (1 × 10 faradios)

Milisegundos (1 × 10 segundos)

6

3

-3

-3

-6

-6

-3

3

MΩ

Hz

kHz

V

mV

A

mA

µA

µF

ms

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5. PRUEBAS ELÉCTRICAS Y MEDICIONES BÁSICAS

Una de las herramientas de diagnóstico eléctrico más común es un multímetro digital (digital multimeter,
DMM). Un DMM es simplemente un patrón electrónico para realizar mediciones eléctricas.

Los DMM tienen muchas funciones y características especiales, pero el uso más común es para medir tensión,
corriente y resistencia. Un multímetro automotor como este multímetro también puede medir frecuencia, RPM,
ciclo de trabajo, permanencia, ancho de pulso, temperatura, capacitancia e, incluso, el estado de los diodos.

Consideraciones generales para realizar mediciones

• Precisión

Un rango de medición determina el valor máximo que el medidor puede medir. La mayoría de las funciones
del medidor tiene más de un rango. Al realizar una medición, es muy importante que se encuentre en
el rango de medición correcto. La selección de un rango inferior mueve el punto decimal un lugar a la
izquierda y aumenta la precisión de la lectura. Cuando la pantalla LCD muestra OFL (sobrecarga), el rango
es demasiado bajo; seleccione el rango superior siguiente.

• Gráfico de barras analógico

El gráco de barras es útil para establecer tendencias o datos direccionales. Es más fácil de leer cuando
los datos generan que la pantalla digital cambie rápidamente.

• Cortador de seguridad

Al medir tensión, asegúrese de que el cable de prueba de color rojo esté conectado al conector de entrada
“ ”; si el cable de prueba de color rojo está conectado al conector “A” o “mA μA”, puede ser objeto
de lesiones o puede dañar el medidor. Al medir corriente, no conecte el cable de prueba de color rojo al
conector de entrada “ ”. Los cortadores de seguridad del medidor se utilizan para evitar la conexión
alterminal de entrada incorrecto.

Mediciones de tensión

Las mediciones de tensión son pruebas dinámicas que miden la tensión en un circuito o componente con
laalimentación encendida. Las mediciones de tensión se llevan a cabo con los cables de prueba conectados
entrelos elementos del circuito bajo prueba.

ADVERTENCIA

PARA EVITAR DESCARGAS ELÉCTRICAS Y DAÑO AL INSTRUMENTO, LA TENSIÓN DE ENTRADA NO DEBE

EXCEDER 1000 V CC O 750 V CA RMS. NO INTENTE MEDIR UNA TENSIÓN DESCONOCIDA QUE PUEDA

EXCEDER 1000 V CC O 750 V CA RMS.

NOTA: Al realizar la medición de tensión, este medidor se debe conectar en paralelo con el circuito o elemento

del circuito bajo prueba.

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Negro Rojo

Conexión en paralelo

Batería de 12 V

Configuración del medidor para medir la tensión:

• Coloque el interruptor giratorio en la conguración de tensión ( o m ). (La conguración m solamente

espara mediciones de milivoltios de CC).

• Presione el botón “DC/AC” (CC/CA) para seleccionar la medición de tensión de CA o CC; la pantalla

mostrará el símbolo correspondiente.

• Inserte el cable de color negro en el conector “COM”.

• Inserte el cable de color rojo en el conector “ ”.

Conecte:

La sonda de color negro al circuito negativo (-) o puesta a tierra.

La sonda de color rojo al circuito que viene desde la fuente de alimentación.

Mediciones de resistencia

La resistencia es una medición estática que signica que debe medirse con la alimentación apagada. Se mide en
ohmios (Ω) y los valores pueden variar en gran medida desde unos pocos miliohmios (mΩ) para la resistencia de
un contacto a miles de millones de ohmios para aislantes.

ADVERTENCIA

APAGUE LA ALIMENTACIÓN Y DESCARGUE TODOS LOS CONDENSADORES DEL CIRCUITO A PROBAR

ANTES DE REALIZAR MEDICIONES DE LA RESISTENCIA EN EL CIRCUITO. LA MEDICIÓN PRECISA

NOESPOSIBLE SI HAY TENSIÓN RESIDUAL O EXTERNA.

NOTA: La resistencia en las sondas de prueba puede afectar la precisión en el rango de 400. Realice el

cortocircuito de las sondas juntas y presione el botón “REL” (Relativo) para restar la resistencia del
cable de prueba de la medición.