Extech Instruments EX320 User manual

User's Guide
Mini Multimeter
with Non-Contact Voltage Detector (NCV)
Model EX320
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com

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Introduction
Congratulations on your purchase of the Extech EX320 Meter. The EX320 offers AC/DC
Voltage, AC/DC Current, Resistance, Diode, Continuity, non-contact Voltage Detection.
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 VAC 600VAC and DC
mAAC/DC 500mADC/AC
AAC/DC 10A DC/AC (for 30 seconds max. every 15
minutes
Resistance, 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. MAX 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
11. RANGE button
12. HOLD button
13. Protective rubber holster (must be removed
to access the rear battery compartment)
Display Symbols and Annunciators
µ micro (10-6) (amps)
m milli (10-3) (volts, amps)
k kilo (103) (ohms)
M mega (106) (ohms)
MAX Highest reading
AC Alternating current
DC Direct current
•))) Continuity
Diode test
Battery status
A Amps
 Ohms
V Volts
AUTO Autoranging
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. 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 EX320 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.
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.

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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  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. 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.
4. 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 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”.

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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.
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.
MAX MODE
Press the MAX button (the MAX icon will appear on the LCD). The meter will now only
display the highest reading during a test. Each time a higher reading is encountered, the
display will update. Press the MAX button again to exit this mode.
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.

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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, 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.