Extech Instruments EX520 User manual

User's Guide
True RMS Industrial Multimeter
Extech EX520

EX520-EU_ENG V2.3 1/08
2
Introduction
Congratulations on your purchase of the Extech EX520 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 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

EX520-EU_ENG V2.3 1/08
3
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.
•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 draining
•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.

EX520-EU_ENG V2.3 1/08
4
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.

EX520-EU_ENG V2.3 1/08
5
Controls and Jacks
1. 6,000 count LCD
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.
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

EX520-EU_ENG V2.3 1/08
6
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.
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.

EX520-EU_ENG V2.3 1/08
7
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 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.
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 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.

EX520-EU_ENG V2.3 1/08
8
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 green 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 the MODE button 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”.
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.

EX520-EU_ENG V2.3 1/08
9
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.
Note: The temperature range of the supplied thermocouple probe is -20 to 250°C (-4 to
482°F)
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.

EX520-EU_ENG V2.3 1/08
10
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 available ranges until you select the desired range.
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.