GB Instruments GMT-19A Manuale utente

Analog Multimeter

Owners Manual Model

• Read this owners manual thoroughly before

use and save.

Gardner

Bender

GMT-19A

OHMS ADJUST

1000V DC/AC

500mA DC

MAX

1000

250

2.5

500m

50m

1000

250

1.5V

X1K

X10

DC10A

–

DC10A

V.Ω.A.

COM

20KΩ/V DC

8KΩ/V AC

1K 100

200

500

000

50 100 150

200

250

20 30

246850

BAT

Ω

BAT

-80+6+12+16+18+20

+22

∞

10 K

+14

1. Meter Functions

Function/

Range

Selector

Switch

Figure 1

Insulated

Test

Leads

Zero

Adjust

Screw

Input Jacks

1.0 Meter Functions

Zero

Ohms

Adjustment

1.0 Meter Functions

2.0 Specifications

2.1 For Your Safety

3.0 Operating Suggestions

3.1 Preliminary Adjustments

3.2 Internal Battery Condition

4.0 DC Voltage Measurement

4.1 Automotive Batteries

4.2 Alternators and Generators

4.3 Household Batteries

5.0 DC Milliamp Measurement

6.0 AC Voltage Measurement

6.1 Wall Receptacles

6.2 Appliance Receptacles

6.3 Circuit Breaker Panels

7.0 Resistance/Continuity Measurement

7.1 Extension Cords

7.2 Appliance Cords

7.3 Fuses

7.4 Switches

7.5 Heating Elements

7.6 Thermostats

8.0 Decibel Measurement

9.0 Battery and Fuse Replacement

Table of Contents

WARNING! Use extreme caution when using

this multimeter. Improper use of this tester can

result in severe damage to property, severe

personal injury or death. Follow all instructions and

suggestions in this operators manual as well as

observing normal electrical safety precautions. Do not

use this multimeter if you are unfamiliar with electrical

circuits and proper test procedures.

2.1 For Your Safety

1) WARNING! Use extreme caution when checking

electrical circuits.

2) WARNING! Do not stand in wet or damp work

areas when working with electricity. Wear

rubber soled boots or shoes.

3) WARNING! Do not apply more voltage or

current than the set range of the multimeter

will allow.

4) Do not touch the metal probes of the test leads when

making a measurement.

5) Replace worn test leads. Do not use test leads with

broken or tattered insulation.

6) Discharge a capacitor before measuring it.

7) Remove the test leads from the circuit being measured

as soon as the test is completed.

8) WARNING! Do not measure voltage when the

function/range switch is set on the resistance

(ohms) or the current (mA) settings. Never measure

current when the tester is set on the resistance range.

Never measure AC voltage when the tester is set on

DC voltage or DCmA/A. Setting the tester on the

incorrect function may burn out some of the internal

circuitry and may pose a safety hazard.

Ranges: 19 measuring ranges

DC Voltage: 2.5-10-50-250-1000 Volts

AC Voltage: 10-50-250-1000 Volts

DC Current 5-50-500 milliAmps (fused)

10 amps on a separate jack (unfused)

Resistance (ohms) Rx1 (resistance indicated multiplied by 1)

Rx10 (resistance indicated multiplied by 10)

Rx1K (resistance indicated multiplied by 1000)

10 Megohm Max

Continuity Buzzer: For audible continuity checks. Buzzer sounds at

less than 100 ohms.

Decibels: -8dB to +22dB on AC voltage ranges

Accuracy: DC voltage, Amps = 4% full scale of range

AC voltage = 5% full scale of range

Resistance = 4% full scale of range

Battery Test: 1.5 volt and 9 volt batteries

Sensitivity: 20,000 ohms per volt DC and 8000 ohms per

volt AC

Operating Temperature: 64°F – 77°F (18°C – 25°C)

Function/Range Switch: 6 Functions

20 Positions

19 Measuring ranges

Zero Ohms Adjustment Dial: Located on the front left side of the housing.

Adjustment dial is used to zero the needle

indicator on the ohms scale while shorting the test

leads together.

Mechanical Zero Located directly below the center of the scale,

Adjustment Screw: used to align needle on the zero settings for

accurate readings.

Mirrored Scale Plate: The mirror on the scale plate is used to line up the

needle with its reflection to improve the reading

accuracy by preventing parallax error.

Recessed Input Jacks: Negative (-) input jack for black test lead, positive

(+) input jack for red test lead. Separate jack for

10 Amp range.

Important:

Read this operators manual thoroughly before using this

multimeter. This manual is intended to provide basic

information regarding this multimeter and to describe

common test procedures which can be made with this unit.

Many types of appliance, machinery and other electrical

circuit measurements are not addressed in this manual and

should be handled by experienced service technicians.

2.0 Specifications

3.2 Check Condition of Internal Battery

Before making resistance or continuity tests, check the

condition of the internal battery. First turn the function/range

switch to the ohms Rx1 position. Short the test leads together

and the needle indicator should deflect to the right side of the

scale. Keep the test leads shorted together while

simultaneously turning the zero ohms adjustment dial until the

needle indicates zero at the right side of the ohms scale. If the

needle will not zero, replace the batteries with two new 1.5 volt

AA size batteries (see Battery Replacement).

1) Fully seat the test leads in the correct input jacks, (-) black

lead, (+) red lead.

1) Set the function/range switch to the proper position

before making a measurement. When the voltage or

current is not known, it MUST be determined that the

capacity of the selected range will handle the amount of

voltage or current in the circuit (see #3 under “For Your

Safety”). Always start with the highest range in the

function. If the voltage applied falls within the range of

a lower setting, reset the function/range switch to the

appropriate setting for greatest accuracy of reading.

2) Avoid placing the tester in areas where vibration, dust or

dirt are present. Do not store the tester in excessively

hot, humid or damp places. This tester is a sensitive

measuring device and should be treated with the same

regard as other electrical and electronic devices.

3) Using the tester in areas with high magnetic fields can

result in inaccurate readings. For greatest accuracy of

reading, lay the tester on a flat, non-metallic surface.

4) When the tester is not in use, keep the function/range

switch in the OFF position. This keeps the needle

indicator from deflecting or “bouncing” excessively.

5) When disconnecting the test leads from the unit, always

grasp the leads where the input jacks meet the tester

housing. Never pull the leads out of the jacks by the

insulated wire or transport the tester using the test leads

as a carrying strap.

6) Never immerse the tester in water or solvents. To clean

the housing use a damp cloth with a minimal amount of

mild soap.

7) If the resistance (ohms) function of the tester is not going

to be used for a week or more, remove the internal

battery to avoid potential leaks that may damage the unit.

3.1 Preliminary Adjustments

Fully seat the test leads in the correct input jacks. If

necessary, using a small flat tip screwdriver, slowly turn the

mechanical zero adjustment screw clockwise or counter-

clockwise until the needle indicator is directly over the three

black zeros at the left end of the scale.

100

200

500

10K

Resistance

(Ohms) Scale

DC Voltage &

Milliamps Scale

Common Markings for

both the AC & DC

Voltage Scales

AC Voltage Scale dB Scale for Transistor

Gain Measurement

}

4.0 DC Voltage Measurement

Reading the Scale

GMT-19A

OHMSADJUST

1000VDC/AC

500mADC

MAX

1000

250

2.5

500m

50m

1000

250

1.5V

X1K

X10

DC10A

–

DC10A

V.Ω.A.

COM

20KΩ/VDC

8KΩ/VAC

1K 100

200

500

000

50 100 150

200

250

20 30

246850

BAT

Ω

BAT

-80+6+12+16+18+20

+22

∞

10 K

+14

Voltage

Scale

Voltage

Range

Black Red

3.0 Operating Suggestions

GB #OX-100 anti-oxidant compound (available at your local

hardware store). Replace and tighten the terminal connectors.

Secondly, if the terminals and connectors are making good

contact, touch the test leads to the battery and vehicle

framework as described above (see fig. 2). Note the reading

of the tester. Get an assistant to turn on the headlights while

the test leads are making contact. The needle indicator should

drop a few volts. Should the needle indicator drop 5 volts or

more, the battery should be charged or possibly replaced if

the voltage drop is significant. The circuit may need to be

checked further for problems within the electrical system that

may be draining the battery.

4.2 Alternators and Generators

Set the function/range switch to the 50 DCV range. While the

engine is idling at normal operating speed, touch the black (-)

test lead to the metal framework of the vehicle, then touch the

red (+) test lead to the output terminal connector. The

alternator output cable is always the heaviest gauge cable

attached to the alternator (see fig. 3). The needle indicator

should read 12 volts or more. If the needle indicator moves

sporadically, the cable may need to be tightened. If the engine

is idling lower than is specified in the vehicle owners manual,

the voltage reading will be lower. If the output voltage is

significantly low, the alternator may require service

or replacement.

WARNING! When making automotive

measurements, observe safety precautions. Stay away from

the fan blades, belts and other moving parts of the engine.

Keep the multimeter and its leads away from moving parts.

Figure 3

2) Set the function/range switch to the appropriate DC

voltage range. If the voltage is unknown, use the highest

range. If the voltage applied falls within the range of a

lower setting, reset the function/range switch to the

appropriate setting for greatest accuracy of reading.

3) If the polarity of the circuit to be tested is known, touch

the black test lead to the neutral side. If the polarity is

unknown, touch the test leads to opposite sides of the

circuit. If the needle indicator deflects to the left of the

scale, reverse the test leads.

Use the chart below as a guide to reading DC

voltage measurements:

DCV Read and

Range Following Multiply

Setting Scale Reading By:

2.5 0-250 Divide Reading by 100

50 0-50 1

250 0-250 1

1000 0-10 100

Common DC Measurements

4.1 Automotive Batteries

Set the function/range switch to 50 DCV. First check the

quality of the battery terminal connector by touching the red

(+) test lead to the connector while touching the black (-) test

lead to any bare metal framework of the vehicle. The tester

should read 12 volts or higher on the 0-50 scale with all of the

vehicle accessories turned off. If the needle indicator moves

sporadically, this indicates a bad terminal connection. Remove

the terminal connectors and clean both terminals and

connectors thoroughly. For improved conductivity and

corrosion resistance, coat the terminals and connectors with

Figure 2

Common DC Milliamperage Measurements

It is important to point out that milliamps can also be

expressed as thousandths of an Ampere. Therefore 500

milliamps is 500 thousandths of one Amp or 1⁄2of one Amp.

The milliamperage function of your multimeter is commonly

used by electronics repair technicians and hobbyists to

troubleshoot various low voltage circuits. Although not

normally used for electrical troubleshooting around the home,

this function can be used to measure the milliamperage draw

of household items such as flashlights and other battery

operated devices that do not draw more than 500mA. In fig. 4,

the red (+) test lead is hooked up to the (+) terminal of the

lantern battery while the black (-) test lead is hooked up to the

bulb. The tester will indicate the milliamperage draw when the

flashlight switch is thrown in the ON position.

WARNING! Do not apply voltage to the

test leads while the tester is set in the milliamp

range. See #8 under For Your Safety.

DC 10Amp Measurement

A separate input jack is provided for measurement of DC

current up to 10 Amps. This range is not fused so it is

imperative that the circuit under test does not exceed 10

Amps. Additionally, this function is designed for intermittent

use only. Maximum contact of the test leads with the circuit

is 15 seconds, with a minimum intermission time of 30

seconds between tests. Set the function/range switch to the

10A range. Touch the test leads to the circuit in the same

manner as instructed in DC MILLIAMPERAGE

MEASUREMENT. Read the 0-10 scale.

4.3 Household Batteries

Household batteries can be tested in either one of two ways.

For a good/bad check, set the function/range switch to the

1.5V or 9V BAT setting depending on which type of battery is

to be tested. Plug the red test lead into the jack marked

“V. Ω.A.”. Touch the red (+) lead to the (+) terminal of the

battery and the black (-) lead to the (-) terminal of the battery.

Read the BAT scale at the very bottom of the scale plate. The

scale will indicate if the battery is good, questionable or should

be replaced. To more accurately measure the voltage value of

household batteries, set the function/range switch to 10 VDC

and touch the leads to the battery as before. Read the 0-10

scale to determine the condition of the battery.

1) Fully seat the test leads in the correct input jacks.

2) Set the function/range switch to the appropriate

DCmA setting.

3) Touch the test leads to the circuit in series (in line with the

circuit) so that the circuit current passes through the

multimeter in order to make the measurement. If the

needle indicator deflects to the left, reverse the test leads.

With a set range of 5mA, read the 0-50 scale and “drop”

the zeros. With a set range of 500mA read the 0-250

scale and multiply the readings by 2.

Figure 4

5.0 DC Milliamp Measurement

GMT-19A

OHMS ADJUST

1000VDC/AC

500mADC

MAX

1000

250

2.5

500m

50m

1000

250

1.5V

X1K

X10

DC10A

–

DC10A

V.Ω.A.

COM

20KΩ/V DC

8KΩ/V AC

1K 100

200

500

000

50 100 150

200

250

20 30

246850

BAT

Ω

BAT

-80+6+12+16+18+20

+22

∞

10 K

+14

DC Milliamp

Scale

DC Milliamp

Measurement

Black Red

Common AC Voltage Measurements

6.1 Wall Receptacles

If the receptacle is controlled by a switch, make sure the

switch is ON. Set the function/range switch to 250 ACV.

Touch the test leads to the “hot”and “neutral”slots of the

receptacle (see fig. 5.) The needle indicator should read 120

VAC on the 0-250 scale. To test for proper grounding of the

receptacle, touch one test lead to the “hot”(narrow) side of

the receptacle, and the other test lead to the ground slot.

The tester should read 120 VAC as before. To test for proper

grounding of non- polarized receptacles (fig.6), alternately

touch the test leads between the receptacle slots and the

wall plate screw. The tester should indicate 120 VAC when

one test lead contacts the “hot”side of the receptacle. If

ground contact cannot be made on the wall plate screw,

remove the wall plate and touch the electrical box with the

test lead in the same manner as before. The tester should

read 120 VAC with one test lead touching the electrical box

and the other touching the live side of the receptacle. If not,

the receptacle is not properly grounded.

1 ) Fully seat the test leads in the correct input jacks.

2) Set the function/range switch to the appropriate AC

voltage range. If the voltage is unknown, use the highest

range. If the voltage applied falls within the range of a

lower setting, reset the function/range switch to the

appropriate setting for greatest accuracy of reading.

3) Touch the test leads to the circuit under test. With AC

voltage, the polarity of the test leads is not a factor.

Use the following chart below as a guide to reading AC

voltage measurements:

ACV Read and

Range Following Multiply

Setting Scale Reading By:

10 0-10 1

50 0-50 1

250 0-250 1

1000 0-10 100

6.0 AC Voltage Measurement

GMT-19A

OHMS ADJUST

1000VDC/AC

500mADC

MAX

1000

250

2.5

500m

50m

1000

250

1.5V

X1K

X10

DC10A

–

DC10A

V.Ω.A.

COM

20KΩ/V DC

8KΩ/V AC

1K 100

200

500

000

50 100 150

200

250

20 30

246850

BAT

Ω

BAT

-80+6+12+16+18+20

+22

∞

10 K

+14

GMT-19A

OHMSADJUST

1000VDC/AC

500mADC

MAX

1000

250

2.5

500m

50m

1000

250

1.5V

X1K

X10

DC10A

–

DC10A

V.Ω.A.

COM

20KΩ/VDC

8KΩ/VAC

1K 100

200

500

000

50 100 150

200

250

20 30

246850

BAT

Ω

BAT

-80+6+12+16+18+20

+22

∞

10 K

+14

5A 5B

Figure 5 Figure 6

AC Scale

in Red

(Use black

numbers on

top for scale.)

AC Voltage

Settings

Red

Black

Neutral Hot

Ground

10 Amp

Scale

Black

Red

scale. If the needle will not zero, replace the internal

batteries with two new 1.5 volt AA size batteries (see

Battery Replacement) .

3) Touch the test leads to the resistance or non-energized

circuit to be measured. Measure the value of the reading

on the ohms scale and multiply the reading by 1000. If

you’re making basic continuity tests, the needle indicator

should move all the way to the right side of the ohms

scale if continuity exists.

Note: When switching the unit back and forth from ohms to

other functions, always zero the needle indicator before

taking another reading. Failure to zero the needle before

taking resistance/continuity measurements will result in

inaccurate readings.

Continuity Buzzer Setting

For quick, audible continuity checks, turn the function/range

switch to the setting. If the circuit under test has a

resistance of 100 ohms or less, the internal buzzer will sound

when the test leads are touched to the circuit. This makes

continuity checks quick and easy. Note: The needle indicator

will not indicate resistance values when the tester is in the

mode. Do not operate the continuity buzzer continuously

as this will discharge the internal batteries.

6.2 Appliance Receptacles

Set the function/range switch to 250 VAC. Touch the test

leads to the receptacle slots. The tester should read 240 VAC

between the two “hot”sides of the receptacle, and 120 VAC

between the neutral slot and either of the two “hot”sides

(see fig. 7).

6.3 Circuit Breaker Panel

To test for defective circuit breakers, set the function/range

switch to the 250 VAC or 600 VAC settings. Touch one test lead

to the neutral (buss) terminal strip of the breaker panel and the

other test lead to the terminal on the circuit breaker (see fig. 8).

The tester should read 120 VAC on the 0-250 scale.

For resistance and circuit continuity testing with power OFF

1) Fully seat the test leads in the input jacks.

2) Set the function/range switch to the Rx1K position and

short the test leads together. Using the zero ohms

adjustment dial, slowly turn the dial until the needle

indicator reads -0- ohms at the right end of the ohms

Figure 7

Figure 8

7.0 Resistance/Continuity Measurement

GMT-19A

OHMS ADJUST

1000VDC/AC

500mADC

MAX

1000

250

2.5

500m

50m

1000

250

1.5V

X1K

X10

DC10A

–

DC10A

V.Ω.A.

COM

20KΩ/V DC

8KΩ/V AC

1K 100

200

500

000

50 100 150

200

250

20 30

246850

BAT

Ω

BAT

-80+6+12+16+18+20

+22

∞

10 K

+14

Resistance

(Ohms) Scale

Top Green

Scale

Zero Ohms

Adjustment

Dial

Black Red

Resistance

(Ohms)

Setting

Audible

Continuity

Should it be determined that the cord is not the source of the

problem, the appliance may need to be disassembled in order

to pinpoint the problem. Refer to the owners manual of the

appliance. The manufacturer of the appliance may require that

the appliance be serviced only by a qualified repair technician.

7.3 Fuses

Note: With the power OFF, always remove a fuse from its

socket before testing it. With cartridge fuses, touch the test

leads to each end of the fuse (see fig. 10). If the fuse is good,

the needle indicator will move to -0- ohms, or if the continuity

buzzer is being used it should sound. If not, replace the fuse.

On plug-type fuses, touch the the test leads on the bottom

contact and the other on the threaded metal contact (see fig.

11). On time-delay/tamper-proof fuses, the other metal contact

is at the top of the ceramic threads.

7.4 Switches

Cut off the power source to the switch. If necessary, remove

the switch from whatever it’s mounted to. Turn the switch to

the ON position and touch the test leads to the switches

terminals (see fig. 12). If the switch is good, the needle

indicator will move to -0- ohms, or if the continuity buzzer is

being used it should sound. If not, replace the switch. On

other than two-way SPST (single pole, single throw)

switches such as three-way light switches or double pole

double throw (ON-OFF-ON) switches, in each ON position

you will need to alternate the test leads between the

switches terminals to determine which two terminals control

that ON position.

Common Resistance and

Continuity Measurements

Continuity tests are probably the most frequently performed

electrical troubleshooting procedures around the home.

ALWAYS REMEMBER THAT CONTINUITY CHECKS ARE

TO BE MADE WITH THE POWER TO THE CIRCUIT

TURNED OFF. Polarity of the test leads is not a factor in

making continuity checks.

7.1 Extension Cords

Unplug the cord. Set the function/range switch to the Rx1K

position. Touch one of the test leads to one of the metal prong

ends of the cord, and insert the other test lead in either one of

the receptacle slots on the other end of the cord, making sure

the test lead is making good contact with the receptacle (see

fig. 9). If the needle indicator does not move to -0- ohms, or if

the continuity buzzer is being used and does not sound, insert

the test lead into the other receptacle slot, again making sure

of good contact. If the needle indicator does not move to -0-

ohms, or if the continuity buzzer is being used and does not

sound, the cord should be replaced.

7.2 Appliance Cords

Unplug the appliance from its power source. Turn its power

switch to the ON position. Touch the test leads to the metal

prong ends of the cord. The tester should indicate a low

resistance value. If not, flex the cord while the leads are still in

contact with the metal prongs. If the needle indicator moves

sporadically, or if the continuity buzzer does not sound, while

the cord flexes, there may be a broken conductor in the cord.

If the needle indicator does not move at all, or the buzzer does

not sound, there may be an open circuit in the appliance.

Figure 11Figure 10

Figure 9

7.5 Heating Elements

Household appliances such as coffee makers and water

heaters contain heating elements which may require

troubleshooting. When making continuity checks on heating

elements, disconnect the element(s) from the circuit(s) that

supply it/them. Touch the test leads, one on each end of the

element and observe the needle indicator. The reading should

indicate low ohms. If the needle indicator doesn’t move, or if

the continuity buzzer is being used and does not sound, the

heating element is broken. If the element(s) show that

continuity exists, test for continuity of the circuit(s) that feed

the element(s) .

7.6 Thermostats

Make sure the thermostat control is in the OFF position.

Remove the thermostat cover. Touch the test leads to the

contact points on the thermostat. The needle indicator should

move to read -0- ohms, or if the continuity buzzer is being

used, it should sound. If not, either one of the contacts may be

loose or broken.

The decibel feature of this multimeter is for transistor gain

measurement in electronic circuits and should not be

confused with audio decibels. This function is used primarily

by electronics technicians to measure the power gain in

transistors, and is rarely encountered in home

project applications.

1) Fully seat the test leads in the correct input jacks.

2) Set the function/range switch to any one of the AC voltage

ranges and read the decibel measurement on the bottom

(red) scale of the faceplate. Based on the AC voltage

8.0 Decibel Measurement

Figure 12 range you selected, you will need to compute the actual

measurement by using the decibel conversion chart

located at the bottom right of the faceplate.

Important: For absolute decibel measurements, circuit

impedance must be at least 600 ohms. -0- decibels = 1

milliwatt in a 600 ohm impedance (equivalent to 0.775 volts

across 600 ohms).

1) Remove the screws in the battery/fuse cover and carefully

separate from the front.

2) Note the polarity of the batteries when removing them

from their compartments and replace.

3) Use GB catalog number GF-0306 .5 Amp/250 Volt

replacement fuses.

4) Carefully replace the battery/fuse cover and tighten the

screws. Do not overtighten the screws as this may strip

the threads in the tester housing.

Order Form

Learn more about using multimeters with "How To Use Your

Multitester For Electrical Testing and Troubleshooting". A

160-page guide to using analog and digital multimeters. Only

available in English. Contains nine chapters of easy to

understand instructions on basic household, automotive

electrical and electronic circuit testing. Packed with

illustrations. Paperback bound. Available wherever

multimeters are sold or:

For customers within the US, send check or money

order for $15.23 per copy ($13.23 plus $2.00 per

copy shipping and handling) to:

Gardner Bender

P.O. Box 3241

Milwaukee, WI 53201-3241

Name

Address

City State Zip

Qty. Ordered

Please print clearly.

9.0 Battery and Fuse Replacement

Indice

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