Extech Instruments EX503 User manual

User's Guide
Autoranging Multimeter
Extech EX503

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Introduction
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.
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.
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
WARNING
CAUTION
MAX
1000V

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CAUTIONS
Improper use of this meter can cause damage, shock, injury or death. Read and understand
this user manual before operating the meter.
Always remove the test leads before replacing the battery or fuses.
Inspect the condition of the test leads and the meter itself for any damage before operating the
meter. Repair or replace any damage before use.
Use great care when making measurements if the voltages are greater than 25VAC rms or
35VDC. These voltages are considered a shock hazard.
Warning! This is a class A equipment. This equipment can cause interferences in the living
quarters; in this case the operator can be required to carry out adequate measures.
Always discharge capacitors and remove power from the device under test before performing
Diode, Resistance or Continuity tests.
Voltage checks on electrical outlets can be difficult and misleading because of the uncertainty
of connection to the recessed electrical contacts. Other means should be used to ensure that
the terminals are not "live".
If the equipment is used in a manner not specified by the manufacturer, the protection provided
by the equipment may be impaired.
This device is not a toy and must not reach children’s hands. It contains hazardous objects as
well as small parts that the children could swallow. In case a child swallows any of them,
please contact a physician immediately
Do not leave batteries and packing material lying around unattended; they can be dangerous
for children if they use them as toys
In case the device is going to be unused for an extended period of time, remove the batteries
to prevent them from training
Expired or damaged batteries can cause cauterization on contact with the skin. Always,
therefore, use suitable hand gloves in such cases
See that the batteries are not short-circuited. Do not throw batteries into the fire.

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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 400mA AC/DC
A AC/DC 10A AC/DC (20A for 30 sec)
Frequency, Resistance, Capacitance,
Diode Test, Continuity 600VDC/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.

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Controls and Jacks
1. 4,000 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. Backlight button
10. REL button
11. HOLD button
Note: Tilt stand and battery compartment are on rear of unit.
Symbols and Annunciators
•))) Continuity
Diode test
Battery status
n nano (10-9) (capacitance)
µ micro (10-6) (amps)
m milli (10-3) (volts, amps)
A Amps
k kilo (103) (ohms)
F Farads (capacitance)
M mega (106) (ohms)
 Ohms
Hz Hertz (frequency) V Volts
% Percent (duty ratio) REL Relative
AC Alternating current Auto Autoranging
DC Direct current HOLD Display hold

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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 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 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.
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 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 4000µA DC, set the function switch to the µA
position and insert the red test lead banana plug into the µA/mA jack.
3. For current measurements up to 400mA DC, set the function switch to the mA
position and insert the red test lead banana plug into the µA/mA jack.
4. For current measurements up to 10A DC, set the function switch to the 10A
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.
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 4000µA AC, set the function switch to the µA
position and insert the red test lead banana plug into the µA/mA jack.
3. For current measurements up to 400mA AC, set the function switch to the mA
position and insert the red test lead banana plug into the µA/mA jack.
4. For current measurements up to 10A AC, set the function switch to the 10A
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 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 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 ΩCAP 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 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 Von 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.

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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 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 Vjack.
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.
Range
( DC/AC )
Sensitivity Frequency width
4V ≥1.5V rms 5Hz~10kHz
40V, 400V ≥10V rms 5Hz~20kHz
≥20V rms 5Hz~200kHz
1000V/1000V ≥420V rms 50Hz~1kHz
400mA ≥45mA rms 5Hz~5kHz
10A ≥4A rms 5Hz~1kHz

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AUTORANGING/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. 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 to switch the display backlight ON. The backlight will automatically
shut off after 20 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 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.