Jensen JTM-105A User manual

User’s Guide
True RMS Industrial Multimeter
Model JTM-105A

Introduction
Congratulations on your purchase of the Jensen JTM-105A True RMS
Autoranging Multimeter. This meter measures AC/DC Voltage, AC/DC
Current, Resistance, Capacitance, Frequency (electrical & electronic),
Diode Test, and Continuity plus Thermocouple Temperature. It features a
waterproof, rugged design for heavy duty use. Proper use and care of this
meter will provide many years of reliable service.
Safety
This symbol adjacent to another symbol, terminal or
operating device indicates that the operator must refer
to an explanation in the Operating Instructions to avoid
personal injury or damage to the meter.
WARNING This WARNING symbol indicates a potentially
hazardous situation, which if not avoided, could result
in death or serious injury.
CAUTION This CAUTION symbol indicates a potentially
hazardous situation, which if not avoided, may result
damage to the product.
MAX
1000V This symbol advises the user that the terminal(s) so
marked must not be connected to a circuit point at
which the voltage with respect to earth ground
exceeds (in this case) 1000 VAC or VDC.
This symbol adjacent to one or more terminals
identifies them as being associated with ranges that
may, in normal use, be subjected to particularly
hazardous voltages. For maximum safety, the meter
and its test leads should not be handled when these
terminals are energized.
This symbol indicates that a device is protected
throughout by double insulation or reinforced
insulation.
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PER IEC1010 OVERVOLTAGE INSTALLATION CATEGORY
OVERVOLTAGE CATEGORY I
Equipment of OVERVOLTAGE CATEGORY I is equipment for
connection to circuits in which measures are taken to limit the transient
overvoltages to an appropriate low level.
Note – Examples include protected electronic circuits.
OVERVOLTAGE CATEGORY II
Equipment of OVERVOLTAGE CATEGORY II is energy-consuming
equipment to be supplied from the fixed installation.
Note – Examples include household, office, and laboratory appliances.
OVERVOLTAGE CATEGORY III
Equipment of OVERVOLTAGE CATEGORY III is equipment in fixed
installations.
Note – Examples include switches in the fixed installation and some
equipment for industrial use with permanent connection to the fixed
installation.
OVERVOLTAGE CATEGORY IV
Equipment of OVERVOLTAGE CATEGORY IV is for use at the origin of
the installation.
Note – Examples include electricity meters and primary over-current
protection equipment

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SAFETY INSTRUCTIONS
This meter has been designed for safe use, but must be operated with
caution. The rules listed below must be carefully followed for safe
operation.
1. NEVER apply voltage or current to the meter that exceeds the
specified maximum:
Input Protection Limits
Function Maximum Input
V DC or V AC 1000VDC/AC rms
mA AC/DC 800mA 1000V fast acting fuse
A AC/DC 10A 1000V fast acting fuse (20A for 30
seconds max every 15 minutes)
Frequency, Resistance,
Capacitance, Diode Test,
Continuity
1000VDC/AC rms
Temperature 1000VDC/AC rms
2. USE EXTREME CAUTION when working with high voltages.
3. DO NOT measure voltage if the voltage on the "COM" input jack
exceeds 600V above earth ground.
4. NEVER connect the meter leads across a voltage source while the
function switch is in the current, resistance, or diode mode. Doing so
can damage the meter.
5. ALWAYS discharge filter capacitors in power supplies and disconnect
the power when making resistance or diode tests.
6. ALWAYS turn off the power and disconnect the test leads before
opening the covers to replace the fuse or batteries.
7. NEVER operate the meter unless the back cover and the battery and
fuse covers are in place and fastened securely.
8. If the equipment is used in a manner not specified by the
manufacturer, the protection provided by the equipment may be
impaired.

Controls and Jacks
1. 6,000 count LCD display
2. RANGE button
3. Hz and % button
4. Mode button
5. Function switch
6. mA, µA and 10A input jacks
7. COM input jack
8. Positive input jack
9. HOLD and Backlight button
10. RELATIVE button
11. MAX/MIN button
Note: Tilt stand and battery compartment are on rear of unit.
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Symbols and Annunciators
Auto power off
•))) Continuity
Diode test
Battery status
n nano (10-9) (capacitance)
µ micro (10-6) (amps, cap)
m milli (10-3) (volts, amps)
A Amps
k kilo (103) (ohms)
F Farads (capacitance)
M mega (106) (ohms)
Ω Ohms
Hz Hertz (frequency) V Volts
% Percent (duty ratio) REL Relative
AC Alternating current AUTO Autoranging
DC Direct current HOLD Display hold
ºF Degrees Fahrenheit ºC Degrees Centigrade
MAX Maximum MIN Minimum
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Operating Instructions
WARNING: Risk of electrocution. High-voltage circuits, both AC and DC,
are very dangerous and should be measured with great care.
1. ALWAYS turn the function switch to the OFF position when the meter
is not in use.
2. If “OL” appears in the display during a measurement, the value
exceeds the range you have selected. Change to a higher range.
DC VOLTAGE MEASUREMENTS
CAUTION: Do not measure DC voltages if a motor on the circuit is
being switched ON or OFF. Large voltage surges may occur that can
damage the meter.
1. Set the function switch to the green VDC position.
2. Insert the black test lead banana plug into the
negative COM jack.
Insert the red test lead banana plug into the positive
Vjack.
3. Touch the black test probe tip to the negative side of
the circuit.
Touch the red test probe tip to the positive side of
the circuit.
4. Read the voltage in the display.
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AC VOLTAGE (FREQUENCY, DUTY CYCLE) MEASUREMENTS
WARNING: Risk of Electrocution. The probe tips may not be long
enough to contact the live parts inside some 240V outlets for
appliances because the contacts are recessed deep in the outlets. As
a result, the reading may show 0 volts when the outlet actually has
voltage on it. Make sure the probe tips are touching the metal contacts
inside the outlet before assuming that no voltage is present.
CAUTION: Do not measure AC voltages if a motor on the circuit is
being switched ON or OFF. Large voltage surges may occur that can
damage the meter.
1. Set the function switch to the green VAC/Hz/% position.
2. Insert the black test lead banana plug into the negative COM jack.
Insert red test lead banana plug into the positive Vjack.
3. Touch the black test probe tip to the neutral side of the circuit.
Touch the red test probe tip to the “hot” side of the circuit.
4. Read the voltage in the display.
5. Press the HZ/% button to indicate “Hz”.
6. Read the frequency in the display.
7. Press the Hz/% button again to indicate “%”.
8. Read the % of duty cycle in the display.
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DC CURRENT MEASUREMENTS
CAUTION: Do not make 20A current measurements for longer than
30 seconds. Exceeding 30 seconds may cause damage to the meter
and/or the test leads.
1. Insert the black test lead banana plug into the negative COM jack.
2. For current measurements up to 6000µA DC, set the function switch to
the yellow µA position and insert the red test lead banana plug into the
µA/mA jack.
3. For current measurements up to 600mA DC, set the function switch to
the yellow mA position and insert the red test lead banana plug into
the µA/mA jack.
4. For current measurements up to 20A DC, set the
function switch to the yellow 10A/HZ/% position
and insert the red test lead banana plug into the
10A jack.
5. Press the MODE button to indicate “DC” on the
display.
6. Remove power from the circuit under test, then
open up the circuit at the point where you wish to
measure current.
7. Touch the black test probe tip to the negative side
of the circuit.
Touch the red test probe tip to the positive side of
the circuit.
8. Apply power to the circuit.
9. Read the current in the display.
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AC CURRENT (FREQUENCY, DUTY CYCLE) MEASUREMENTS
CAUTION: Do not make 20A current measurements for longer than
30 seconds. Exceeding 30 seconds may cause damage to the meter
and/or the test leads.
1. Insert the black test lead banana plug into the negative COM jack.
2. For current measurements up to 6000µA AC, set the function switch
to the yellow µA position and insert the red test lead banana plug into
the µA/mA jack.
3. For current measurements up to 600mA AC, set the function switch
to the yellow mA position and insert the red test lead banana plug
into the µA/mA jack.
4. For current measurements up to 20A AC, set the function switch to
the yellow 10A/HZ/% position and insert the red test lead banana
plug into the 10A jack.
5. Press the MODE button to indicate “AC” on the display.
6. Remove power from the circuit under test, then open up the circuit at
the point where you wish to measure current.
7. Touch the black test probe tip to the neutral side of the circuit.
Touch the red test probe tip to the “hot” side of the
circuit.
8. Apply power to the circuit.
9. Read the current in the display.
10.Press the Hz/% button to indicate “Hz”.
11.Read the frequency in the display.
12.Press the Hz/% button again to indicate “%”.
13.Read the % duty cycle in the display.
14.Press the Hz/% button to return to current
measurement.
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RESISTANCE MEASUREMENTS
WARNING: To avoid electric shock, disconnect power to the unit
under test and discharge all capacitors before taking any resistance
measurements. Remove the batteries and unplug the line cords.
1. Set the function switch Ω CAP position.
2. Insert the black test lead banana plug into the
negative COM jack.
Insert the red test lead banana plug into the positive
Ωjack.
3. Press MODE to indicate “Ω" on the display.
4. Touch the test probe tips across the circuit or part
under test. It is best to disconnect one side of the
part under test so the rest of the circuit will not
interfere with the resistance reading.
5. Read the resistance in the display.
CONTINUITY CHECK
WARNING: To avoid electric shock, never measure continuity on
circuits or wires that have voltage on them.
1. Set the function switch to the green ΩCAP
position.
2. Insert the black lead banana plug into the negative
COM jack.
Insert the red test lead banana plug into the
positive Ωjack.
3. Press the MODE button to indicate” "and “Ω”on
the display
4. Touch the test probe tips to the circuit or wire you
wish to check.
5. If the resistance is less than approximately 35Ω,
the audible signal will sound. If the circuit is open,
the display will indicate “OL”.
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DIODE TEST
1. Set the function switch to the green ΩCAP
position.
2. Insert the black test lead banana plug into the
negative COM jack and the red test lead banana
plug into the positive Vjack.
3. Press the MODE button to indicate and Von the
display.
4. Touch the test probes to the diode under test.
Forward voltage will typically indicate 0.400 to
0.700V. Reverse voltage will indicate “OL”. Shorted
devices will indicate near 0V and an open device will
indicate “OL” in both polarities.
TEMPERATURE MEASUREMENTS
1. Set the function switch to the green Temp
position.
2. Insert the Temperature Probe into the input
jacks, making sure to observe the correct
polarity.
3. Press the MODE button to indicate ºF or ºC
4. Touch the Temperature Probe head to the part
whose temperature you wish to measure.
Keep the probe touching the part under test
until the reading stabilizes (about 30 seconds).
5. Read the temperature in the display.
Note: The temperature probe is fitted with a type K mini connector. A mini
connector to banana connector adaptor is supplied for connection to
the input banana jacks.
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CAPACITANCE MEASUREMENTS
WARNING: To avoid electric shock, disconnect power to the unit
under test and discharge all capacitors before taking any capacitance
measurements. Remove the batteries and unplug the line cords.
1. Set the rotary function switch to the green ΩCAP position.
2. Insert the black test lead banana plug into the negative
COM jack.
Insert the red test lead banana plug into the positive V
jack.
3. Press the MODE button to indicate “nF” on the
display.
4. Touch the test leads to the capacitor to be tested.
5. The test may take up to 3 minutes or more for large
capacitors to charge. Wait until the readings settle
before ending the test.
6. Read the capacitance value in the display
FREQUENCY/DUTY CYCLE MEASUREMENTS (ELECTRONIC)
1. Set the rotary function switch to the green “Hz %”
position.
2. Press the Hz/% button to indicate “Hz” in the display.
3. Insert the black lead banana plug into the negative
COM jack and the red test lead banana plug into the
positive Hz jack.
4. Touch the test probe tips to the circuit under test.
5. Read the frequency on the display.
6. Press the Hz/% button again to indicate “%” on the
display.
7. Read the % of duty cycle on the display.
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AUTO / MANUAL RANGE SELECTION
When the meter is first turned on, it automatically goes into Autoranging.
This automatically selects the best range for the measurements being
made and is generally the best mode for most measurements. For
measurement situations requiring that a range be manually selected,
perform the following:
1. Press the RANGE key. The “AUTO” display indicator will turn off.
2. Press the RANGE key to step through the available ranges until you
select the range you want.
3. To exit the Manual Ranging mode and return to Autoranging, press
and hold the RANGE key for 2 seconds.
Note: Manual ranging does not apply for the Capacitance and
Frequency functions.
MAX/MIN
Note: When using the MAX/MIN function in Autoranging mode, the
meter will “lock” into the range that is displayed on the LCD when
MAX/MIN is activated. If a MAX/Min reading exceeds that range,
an “OL” will be displayed. Select the desired range BEFORE
entering MAX/MIN mode.
1. Press the MAX/MIN key to activate the MAX/MIN recording mode. The
display icon "MAX" will appear. The meter will display and hold the
maximum reading and will update only when a new “max” occurs.
2. Press the MAX/MIN key again and the display icon "MIN" will appear.
The meter will display and hold the minimum reading and will update
only when a new “min” occurs.
3. To exit MAX/MIN mode press and hold the MAX/MIN key for 2
seconds.

RELATIVE MODE
The relative measurement feature allows you to make measurements
relative to a stored reference value. A reference voltage, current, etc.
can be stored and measurements made in comparison to that value.
The displayed value is the difference between the reference value and
the measured value.
1. Perform the measurement as described in the operating instructions.
2. Press the REL button to store the reading in the display and the "REL"
indicator will appear on the display.
3. The display will now indicate the difference between the stored value
and the measured value.
4. Press the REL button to exit the relative mode.
Note: The Relative function does not operate in the Frequency function.
DISPLAY BACKLIGHT
Press the HOLD key for >1 second to turn on or off the display backlight
function. The backlight will automatically turn off after 10 seconds.
HOLD
The hold function freezes the reading in the display. Press the HOLD
key momentarily to activate or to exit the HOLD function.
AUTO POWER OFF
The auto off feature will turn the meter off after 15 minutes. To disable
the auto power off feature, hold down the MODE button and turn the
meter on.
LOW BATTERY INDICATION
The icon will appear in the lower left conner of the display when the
battery voltage becomes low. Replace the battery when this appears.
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Maintenance
WARNING: To avoid electric shock, disconnect the test leads from any
source of voltage before removing the back cover or the battery or fuse
covers.
WARNING: To avoid electric shock, do not operate your meter until the
battery and fuse covers are in place and fastened securely.
This MultiMeter is designed to provide years of dependable service, if the
following care instructions are performed:
1. KEEP THE METER DRY. If it gets wet, wipe it off.
2. USE AND STORE THE METER IN NORMAL TEMPERATURES.
Temperature extremes can shorten the life of the electronic parts and
distort or melt plastic parts.
3. HANDLE THE METER GENTLY AND CAREFULLY. Dropping it can
damage the electronic parts or the case.
4. KEEP THE METER CLEAN. Wipe the case occasionally with a damp
cloth. DO NOT use chemicals, cleaning solvents, or detergents.
5. USE ONLY FRESH BATTERIES OF THE RECOMMENDED SIZE
AND TYPE. Remove old or weak batteries so they do not leak and
damage the unit.
6. IF THE METER IS TO BE STORED FOR A LONG PERIOD OF TIME,
the batteries should be removed to prevent damage to the unit.

BATTERY INSTALLATION
WARNING: To avoid electric shock, disconnect the test leads from any
source of voltage before removing the battery cover.
1. Turn power off and disconnect the test leads from the meter.
2. Open the rear battery cover by removing two screws (B) using a
Phillips head screwdriver.
3. Insert the battery into battery holder, observing the correct polarity.
4. Put the battery cover back in place. Secure with the screws.
WARNING: To avoid electric shock, do not operate the meter until the
battery cover is in place and fastened securely.
NOTE: If your meter does not work properly, check the fuses and batteries
to make sure that they are still good and that they are properly
inserted.
AA
A
B
B
F1 F2
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REPLACING THE FUSES
WARNING: To avoid electric shock, disconnect the test leads from any
source of voltage before removing the fuse cover.
1. Disconnect the test leads from the meter.
2. Remove the protective rubber holster.
3. Remove the battery cover (two “B” screws) and the battery.
4. Remove the six “A” screws securing the rear cover.
5. Gently remove the old fuse and install the new fuse into the holder.
6. Always use a fuse of the proper size and value (0.8A/1000V fast blow
for the 600mA range [SIBA 70-172-40], 10A/1000V fast blow for the
20A range [SIBA 50-199-06]).
7. Replace and secure the rear cover, battery and battery cover.
WARNING: To avoid electric shock, do not operate your meter until the
fuse cover is in place and fastened securely.

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Specifications
Function Range Resolution Accuracy
600mV 0.1mV
6V 0.001V
60V 0.01V
600V 0.1V
DC
Voltage
1000V 1V
±(0.09% reading + 2 digits)
50 to 60Hz 40Hz to 1KHz
6V 0.001V
60V 0.01V
600V 0.1V
AC
Voltage
1000V 1V
±(1.0% reading +
3 dgts)
±(2.0% reading + 3
dgts)
All AC voltage ranges are specified from 5% of range to 100%
of range
600μA 0.1μA
6000μA 1μA
60mA 0.01mA
600mA 0.1mA
6A 0.001A
10A 0.01A
±(1.0% reading + 3 digits)
DC
Current
(20A: 30 sec max with reduced accuracy)
40Hz to 1kHz
600μA 0.1μA
6000μA 1μA
60mA 0.01mA
600mA 0.1mA
6A 0.001A
10A 0.01A
±(1.5% reading + 3 digits)
AC
Current
(20A: 30 sec max with reduced accuracy)
All AC voltage ranges are specified from 5% of range to 100%
of range
NOTE: Accuracy is stated at 65oF to 83oF (18oC to 28oC) and less than
75% RH.

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Function Range Resolution Accuracy
600Ω0.1Ω
6kΩ0.001kΩ
60kΩ0.01kΩ
600kΩ0.1kΩ
6MΩ0.001MΩ
±(0.3% reading + 4 digits)
Resistance
60MΩ0.01MΩ±(0.3% reading + 20 digits)
60nF 0.01nF
600nF 0.1nF
6μF 0.001μF
60μF 0.01μF
600μF 0.1μF
±(3.5% reading + 4 digits)
Capacitance
1000μF 1μF ±(5% reading + 5 digits)
9.999Hz 0.001Hz
99.99Hz 0.01Hz
999.9Hz 0.1Hz
9.999kHz 0.001kHz
99.99kHz 0.01kHz
999.9kHz 0.1kHz
9.999MHz 0.001MHz
40MHz .01MHz
±(0.1% reading + 1 digits)
Frequency
(electronic)
Sensitivity: 0.8V rms min. @ 20% to 80% duty cycle and <100kHz;
5Vrms min @ 20% to 80% duty cycle and > 100kHz.
10.00-
400Hz
0.01Hz ±(0.5% reading) Frequency
(electrical)
Sensitivity: 15Vrms
0.1 to
99.9%
0.1% ±(1.2% reading + 2 digits) Duty Cycle
Pulse width: 100µs - 100ms, Frequency: 5Hz to 150kHz
-50 to
1382°F
1°F
Temp
(type-K)
-45 to
750°C
1°C
±(3.0% reading + 5°C /9°F
digits)
(probe accuracy not included)