Congratulations on your purchase of the Extech EX503 Autoranging Multimeter. This meter measures
AC/DC Voltage, AC/DC Current, Resistance, Capacitance, Frequency, 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
CAUTION
MAX
1000V
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
This WARNING symbol indicates a potentially hazardous situation, which if not
avoided, could result in death or serious injury.
This CAUTION symbol indicates a potentially hazardous situation, which if not
avoided, may result damage to the product.
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.
Note: Tilt stand and battery compartment are on rear of unit.
Symbols and Annunciators
•))) Continuity
Diode test
Battery status
n nano (10
µ micro (10
m milli (10
A Amps
k kilo (10
F Farads (capacitance)
M mega (10
Ohms
Hz Hertz (frequency) V Volts
% Percent (duty ratio) REL Relative
AC Alternating current Auto Autoranging
DC Direct current HOLD Display hold
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 VDC or mVDC 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. 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.
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 VAC position.
2. Insert the black test lead banana plug into the negative COM jack.
Insert red test lead banana plug into the positive V jack.
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.
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 to the 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 jack.
3. Press the MODE button to indicate “"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 Ω CAP position.
2. Insert the black lead banana plug into the negative COM jack.
Insert the red test lead banana plug into the positive jack.
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 100, the audible signal will sound. If
the circuit is open, the display will indicate “OL”.
DIODE TEST
1. Set the function switch to the Ω CAP position.
2. Insert the black test lead banana plug into the negative COM jack and the red test
lead banana plug into the positive V jack.
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.
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 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 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 “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.
FREQUENCY SENSITIVITY (ELECTRICAL)
The frequency sensitivity is range dependent when the Hz function is selected while in the voltage
or current measuring mode. Below are typical sensitivities for the “electrical” measurement modes.
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. Observe the decimal point and units
displayed until the preferred range is located.
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 or for the mV
range.
RELATIVE MODE
The relative measurement feature allows you to make measurements relative to a stored zero
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 (zero) 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 backlight button for >2 second to turn on. Press the button again to turn the backlight
off.
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 30 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 display when the battery voltage becomes low. Replace the battery
when this appears.
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.
Disposal: Do not dispose of this instrument in household waste. The user is obligated to take end-oflife devices to a designated collection point for the disposal of electrical and electronic equipment.
Other Battery Safety Reminders
o Never dispose of batteries in a fire. Batteries may explode or leak.
o Never mix battery types. Always install new batteries of the same type.
Never dispose of used batteries or rechargeable batteries in household waste.
As consumers, users are legally required to take used batteries to appropriate
collection sites, the retail store where the batteries were purchased, or wherever
batteries are sold.
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.
A
A
B
B
A
F1 F2
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 battery cover (two “B” screws) and the battery.
3. Remove the six “A” screws securing the rear cover.
4. Gently remove the old fuse and install the new fuse into the holder.
5. Always use a fuse of the proper size and value (0.5A/1000V fast blow for the 400mA range [SIBA
70-172-40], 10A/1000V fast blow for the 20A range [SIBA 50-199-06]).
6. 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.
(+ digits) – This is the accuracy of the analog to digital converter.
Enclosure Double molded, waterproof (IP67)
Shock (Drop Test) 2 meters (6.5 feet)
Diode Test Test current of 0.3mA typical, open circuit voltage 1.5V DC typical
Continuity Check Audible signal will sound if the resistance is less than 100 (approx.), test
current <0.3mA
Input Impedance 7.8MΩ
AC Response Average responding
ACV Bandwidth 50Hz to 400Hz
Crest Factor ≤3 at full scale up to 500V, decreasing linearly to ≤1.5 at 1000V
Display 4,000 count backlit liquid crystal
Overrange indication “OL” is displayed
Auto Power Off 30 minutes (approximately)
Polarity Automatic (no indication for positive); Minus (-) sign for negative
Measurement Rate 2 times per second, nominal
Low Battery Indication “ ” is displayed if battery voltage drops below operating voltage
Battery One 9 volt (NEDA 1604) battery
Fuses mA, µA ranges; 0.5A/1000V ceramic fast blow
A range; 10A/1000V ceramic fast blow
Operating Temperature 5C to 40C (41F to 104F)
Storage Temperature -20C to 60C (-4F to 140F)
Operating Humidity Max 80% up to 31C (87F) decreasing linearly to 50% at 40C (104F)
Storage Humidity <80%
Operating Altitude 2000meters (7000ft) maximum
Weight 342g (0.753lb) (includes holster).
Size 182 x 82 x 55mm (7.2” x 3.2” x 2.2”)
Safety This meter is intended for origin of installation use and protected, against
the users, by double insulation per EN61010-1 and IEC61010-1 2
(2001) to Category IV 600V and Category III 1000V; Pollution Degree 2.
The meter also meets UL 61010-1, 2
61010-1 2
nd
Edition (2004), and UL 61010B-2-031, 1st Edition (2003)
nd
Edition (2004), CAN/CSA C22.2 No.
nd
Edition
Approvals UL CE
UL Listed The UL mark does not indicate that this product has been evaluated for the