Extech Instruments 411 User manual

User's Guide
True RMS Multimeter
Extech 411

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Introduction
Congratulations on your purchase of the Extech 411 (part number EX411) True RMS Multimeter. This
meter measures AC/DC Voltage, AC/DC Current, Resistance, Diode Test, and Continuity plus
Thermocouple Temperature. Proper use and care of this meter will provide many years of reliable
service.
Safety
International Safety Symbols
This symbol, adjacent to another symbol or terminal, indicates the user must refer
to the manual for further information.
This symbol, adjacent to a terminal, indicates that, under normal use, hazardous
voltages may be present
Double insulation
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.
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.
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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OVERVOLTAGE CATEGORY III
This meter meets the IEC 610-1-2001 standard for OVERVOLTAGE CATEGORY III. Cat III meters
are protected against overvoltage transients in fixed installation at the distribution level. Examples
include switches in the fixed installation and some equipment for industrial use with permanent
connection to the fixed installation.
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
VAC 750V DC/AC
V DC or V AC 1000V DC/AC, 200Vrms on 200mV range
mA DC 200mA 250V fast acting fuse
A DC 20A 250V fast acting fuse(30 seconds max every 15 minutes)
Ohms, Continuity 250Vrms for 15sec max
2. USE EXTREME CAUTION when working with high voltages.
3. DO NOT measure voltage if the voltage on the "COM" input jack exceeds 1000V 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 battery.
7. NEVER operate the meter unless the back cover and the battery cover is in place and fastened
securely.

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Controls and Jacks
1. Rubber holster
2. 2000 count LCD display
3. °F button
4. °C button
5. Function switch
6. mA, uA and A input jacks
7. COM input jack
8. Positive input jack
9. Battery check button
10. Hold button
11. Backlight button
Note: Tilt stand and battery compartment are on rear of unit.
Symbols and Annunciators
•))) Continuity
Diode test
Battery status
Test lead connection
error
µ micro (10-6) (amps)
m milli (10-3) (volts, amps)
k kilo (103) (ohms)
M mega (106) (ohms)  Ohms
A Amps V Volts
AC Alternating current AUTO Autoranging
DC Direct current HOLD Display hold
ºF Degrees Fahrenheit ºC Degrees Centigrade

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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 “1 ” appears in the display during a measurement, the value exceeds the range you have
selected. Change to a higher range.
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.
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 highest V DC ( ) 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. Reset the function switch to
successively lower V DC positions to obtain a higher resolution reading.
If the polarity is reversed, the display will show (-) minus before the
value.

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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 highest V AC ( ) 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. Reset the function switch to
successively lower V AC positions to obtain a higher resolution reading.
DC CURRENT MEASUREMENTS
CAUTION: Do not make current measurements on the 20A scale 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 200µA DC, set the function
switch to the 200µA DC ( ) position and insert the red test
lead banana plug into the uA/mA jack.
3. For current measurements up to 200mA DC, set the function
switch to the 200mA DC position and insert the red test lead
banana plug into the uA/(mA jack.
4. For current measurements up to 20A DC, set the function switch
to the 20A DC range and insert the red test lead banana plug into
the 20A jack.
5. Remove power from the circuit under test, then open up the circuit
at the point where you wish to measure current.
6. 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.
7. Apply power to the circuit.
8. Read the current in the display.

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AC CURRENT MEASUREMENTS
CAUTION: Do not make current measurements on the 20A scale 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 200mA AC, set the function
switch to the highest 200mA AC ( ) position and insert the red
test lead banana plug into the mA jack.
3. For current measurements up to 20A AC, set the function switch
to the 20A AC range and insert the red test lead banana plug into
the 20A jack.
4. Remove power from the circuit under test, then open up the circuit
at the point where you wish to measure current.
5. 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.
6. Apply power to the circuit.
7. 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 battery and unplug the line
cords.
1. Set the function switch to the highest  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 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.
4. Read the resistance in the display and then set the function switch to
the lowest position that is greater than the actual or any anticipated
resistance.

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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.
Insert the red test lead banana plug into the positive jack.
3. Touch the test probe tips to the circuit or wire you wish to check.
4. If the resistance is less than approximately 150, the audible signal
will sound. If the circuit is open, the display will indicate “1”.
DIODE TEST
1. Insert the black test lead banana plug into the negative COM jack and
the red test lead banana plug into the positive diode jack.
2. Turn the rotary switch to the position.
3. Touch the test probes to the diode under test. Forward bias will
typically indicate 400 to 1000. Reverse bias will indicate “1 ”.
Shorted devices will indicate near 0 and the continuity beeper will
sound. An open device will indicate “1 ” in both polarities.

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TEMPERATURE MEASUREMENTS
1. Set the function switch to the TEMP position.
2. Insert the Temperature Probe into the Temperature Socket,
making sure to observe the correct polarity.
3. Press the ºC or ºF button for the desired units.
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.
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.
DISPLAY BACKLIGHT
Press and hold the button to turn on the display backlight function. The backlight will
automatically turn off after 15 seconds.
BATTERY CHECK
The CHECK function tests the condition of the 9V battery. Set the function switch to the
200VDC range and press the CHECK button. If the reading is less than 8.5, battery replacement is
recommended.
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.
LOW BATTERY INDICATION
If the icon appears in the display, the battery voltage is low and the battery should be replaced.
WRONG CONNECTION INDICATION
The icon will appear in the upper right conner of the display and the buzzer will sound
whenever the positive test lead is inserted into the 20A or uA/mA input jack and a non-current
(green) function is selected. If this occurs, turn the meter off and reinsert the test lead into the
proper input jack for the function selected.