Extech Instruments EX330 User manual

User Guide
Mini Multimeter
with Non-Contact Voltage Detector (NCV)
Model EX330

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Introduction
Congratulations on your purchase of the Extech EX330 Meter. The EX330 offers AC/DC Voltage,
AC/DC Current, Resistance, Diode, Continuity, non-contact Voltage Detection, Capacitance,
Frequency, Duty Cycle, and Temperature (Type K) functions. 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 600V.
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.
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 600V AC and DC
mA AC/DC 500mA DC/AC
A AC/DC 10A DC/AC (for 30 seconds max. every 15 minutes
Frequency, Resistance, Capacitance, Duty
Cycle, Diode Test, Continuity
250V DC/AC
Temperature 250V DC/AC
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 power and disconnect test leads before opening the covers to replace the fuse
or battery.
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.
WARNING
CAUTION
MAX
600V

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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.
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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Controls and Jacks
1. AC Voltage Detector Sensor
2. AC Voltage Detector indicator light
3. LCD
4. RELATIVE push-button
5. MODE button
6. Non-contact AC Voltage Detector test button
7. Rotary function dial
8. 10 ampere test lead jack
9. COM test lead jack
10. Test lead jack for voltage, milli-amp, micro-amp, resistance,
capacitance, frequency, and temperature functions
11. RANGE button
12. HOLD button
13. Protective rubber holster (must be removed to access the
rear battery compartment)
Display Symbols and Annunciators
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)  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
•))) Continuity
Diode test
Battery status
1
2
3
4
5
6
7
8
12
13
11
10
9

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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. Press the HOLD button to freeze a displayed reading
NOTE: On some low AC and DC voltage ranges, with the test leads not connected to a device, the
display may show a random, changing reading. This is normal and is caused by the high-input
sensitivity. The reading will stabilize and give a proper measurement when connected to a
circuit.
NON-CONTACT AC VOLTAGE DETECTOR
The EX330 can detect the presence of AC voltage (from 100 to 600VAC) simply by being held very
near to a voltage source.
WARNING: Test the AC voltage detector on a known live circuit before each use.
WARNING: Before using the meter in the AC Voltage Detector mode, verify that the battery is
fresh by confirming characters appear on the LCD when the function dial is turned to any
position. Do not attempt to use the meter as an AC Voltage Detector if the battery is weak or bad.
The NCV function works on any rotary switch position.
1. Test the detector on a known live circuit before use.
2. Press and hold the NCV button for the duration of the test. The meter will
beep once when the button is pushed.
3. Hold the top of the meter very close to the voltage source as shown.
4. If voltage is present, the rim of the LCD display will flash a bright orange and
an audible warning will sound.

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AC VOLTAGE 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.
4. Touch the red test probe tip to the “hot” side of circuit.
5. Read the voltage in the display.
6. If the measured AC voltage exceeds the highest range of the meter
(refer to the specification table) an audible tone will sound.
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 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 / DC CURRENT MEASUREMENTS
CAUTION: Do not make current measurements at 10 Amps 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, set the function switch to the µA position and insert
the red test lead banana plug into the mA/µA jack
3. For current measurements up to 400mA, set the function switch to the mA position and insert
the red test lead banana plug into the mA/µA jack.
4. For current measurements up to 10A, set the function switch to the 10A range and insert the
red test lead banana plug into the 10A jack.
5. Use the MODE button to select AC or DC current. The display will reflect the selection.
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.
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  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. Use the MODE button to view the icononthedisplay
4. Touch the test probe tips across the circuit or component under test. It is
best to disconnect one side of the circuit under test so the rest of the
circuit will not interfere with the resistance reading.
5. Read the resistance in the display.

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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 position.
2. Insert the black lead banana plug into the negative COM jack.
3. Insert the red test lead banana plug into the positive jack.
4. Use the MODE button to view the icon on the display.
5. Touch the test probe tips to the circuit or wire you wish to check.
6. If the resistance is less than approximately 100, the audible signal
will sound. If the circuit is ‘open’ (bad), the display will indicate “OL”.
DIODE TEST
1. Set the function switch to the position.
2. Insert the black test lead banana plug into the negative COM jack and
the red test lead banana plug into the positive jack.
3. Use the MODE button to view the icon 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.
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 CAP position.
2. Insert the black test lead banana plug into the negative COM jack.
3. Insert the red test lead banana plug into the positive CAP jack.
4. Use the MODE button to view the unit of measurement.
5. Touch the test leads to the capacitor to be tested.
6. The test may take up to 3 minutes or more for large capacitors to
charge. Wait until the readings settle before ending the test.
7. Read the capacitance value in the display

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FREQUENCY MEASUREMENTS
1. Use the MODE button to view the Hz unit of measure on the LCD
display.
2. Insert the black test lead banana plug into the negative COM jack and
the red test lead banana plug into the positive Hz jack.
3. Touch the test probe tips to the circuit under test.
4. Read the frequency on the display.
% DUTY CYCLE
1. Set the rotary function switch to the Hz/% position.
2. Use the MODE button to view the %unit of measure on the LCD 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 % duty cycle on the display.
CONTACT TEMPERATURE MEASUREMENTS
1. Set the function switch to the ºF or ºC position.
2. Insert the Temperature Probe into the input jacks, making sure to observe
polarity.
3. The probe can be pressed against a device under test to read its temperature
or the probe can be held in air to read the ambient temperature. Allow 30
seconds for the display to stabilize.
4. Read the temperature in the display.
Note: The temperature range of the supplied thermocouple probe is -20 to 250°C (-4
to 482°F)
AUTO-MANUAL RANGE SELECTION
When the meter is first turned on, it automatically goes into the Auto Range mode. 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 RANGE to step through the available ranges until the desired range is selected.
3. To exit the Manual Ranging mode and return to Auto Range, press and hold the RANGE key
for 2 seconds.
Note: Manual range does not apply to Capacitance, Frequency or Temperature modes.

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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 so that subsequent measurements can be
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 (the REL indicator will appear on the display).
3. The display will now indicate the difference between stored value and subsequent
measurements.
4. Press the REL button to exit the relative mode.
Note: The Relative mode is not available when measuring Frequency or Duty Cycle.
AUTO POWER OFF
The meter will automatically turn off after 15 minutes of inactivity. This will conserve battery energy. To
turn the meter on after an Auto Power OFF, simply turn the rotary switch to OFF and then back to the
desired setting.
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, dry it immediately.
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.