Extech EX840 Operating Manual

User's Guide

Extech EX840 True RMS 1000 Amp
Clamp Meter with IR Thermometer

Introduction

Congratulations on your purchase of the Extech EX840 CAT IV True RMS 1000A Clamp
Meter. This meter measures AC/DC Voltage, AC/DC Current, Resistance, Capacitance,
Frequency, Duty Cycle, Diode Test, Continuity, Type k thermocouple thermometer plus
Non-Contact IR 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

SAFETY NOTES

• Do not exceed the maximum allowable input range of any function.

• Do not apply voltage to meter when resistance function is selected.

• Set the function switch OFF when the meter is not in use.

• Remove the battery if meter is to be stored for longer than 60 days.

WARNINGS

• Set function switch to the appropriate position before measuring.

• When measuring volts do not switch to current/resistance modes.

• Do not measure current on a circuit whose voltage exceeds 600V.

• When changing ranges always disconnect the test leads from the circuit under test.

Function Maximum Input

A AC, ADC 1000A DC/AC
V DC, V AC 1000V DC/AC
Resistance, Capacitance, Frequency, Diode Test 250V DC/AC
Type K Temperature 60V DC, 24V AC

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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.

• Do not directly view or direct the laser pointer at an eye. Low power visible lasers

do not normally present a hazard, but may present some potential for hazard if
viewed directly for extended periods of time

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Description

Meter Description

1. Current clamp

2. Clamp opening trigger

3. Data Hold Button

4. Mode

5. Peak

6. Range

7. DCA Zero

8. MIN/MAX

9. Backlit LCD Display

10. Test lead input jacks

11. IR thermometer and laser pointer (rear)

12. Backlight Button

13. Laser pointer button

14. Function switch

Display icons Description

HOLD Data Hold
Minus sign Negative reading display
0 to 3999 Measurement display digits
ZERO Zero
P Peak value
AUTO Auto Range mode
DC/AC Direct Current / Alternating

MAX Max reading
MIN Min reading
Low battery
mV or V Milli-volts or Volts (Voltage)
Ω Ohms (Resistance)
A Amperes (Current)
F Farad (Capacitance)
Hz Hertz (Frequency)

o

F and oC Fahrenheit and Celsius units (Temperature)

n, m, μ, M, k Unit of measure prefixes: nano, milli, micro, mega, and kilo

)

)

•

) Continuity test

Current

Diode test
Laser pointer

1

2

3

5

6

9

10

11

12

13

14

8

4
7

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Operation

NOTES: Read and understand all Warning and Caution statements in this operation
manual prior to using this meter. Set the function select switch to the OFF position when
the meter is not in use.

AC Current Measurements

WARNING: Ensure that the test leads are disconnected from the meter before making

current clamp measurements.

1. Set the Function switch to the A

DC range

or A

2. Press the trigger to open the jaw.
Fully enclose only one conductor.
For optimum results, center the
conductor in the jaw.

3. The clamp meter LCD will display
the reading.

DCA ZERO
The DC Zero feature removes offset

values and improves accuracy for DC
current measurements. To perform a
zero, select ADC and with no
conductor in the jaw:

1. Press the DC ZERO button to
zero the display. “ZERO” will appear in the display. The offset value is now stored and
removed from all measurements.

2. To view the stored value, press the DC ZERO button. “ZERO” will flash and the
stored value will be displayed.

3. To exit this mode, press and Hold the ZERO button until “ZERO” is no longer in the
display.

AC

Correct

Incorrect

AC/DC Voltage Measurements

1. Insert the black test lead into the negative COM terminal and the red
test lead into the positive V terminal.

2. Set the function switch to the V

3. Use the MODE button to select AC or DC Voltage).

4. Connect the test leads in parallel to the circuit under test.

5. Read the voltage measurement on the LCD display.

AC or VDC position.

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Resistance Measurements

Note: Remove power before making resistance measurements

1. Insert the black test lead into the negative COM terminal and the red
test lead into the Ω positive terminal.

2. Set the function switch to the Ω position.

3. Touch the test probe tips across the circuit or component under test.

4. Read the resistance on the LCD display.

Capacitance Measurements

WARNING: To avoid electric shock, discharge the capacitor under test

1. Set the function switch to the

2. Insert the black test lead banana plug into the negative COM jack

3. Press MODE to zero any stray capacitance.

4. Touch the test probe tips across the part under test.

5. Read the capacitance value in the display.

6. The display will indicate the proper decimal point and value.

before measuring. If “dISC” appears in the display, remove
and discharge the capacitor.

capacitance position.

and the red test lead banana plug into the CAP positive jack.

Ù

Note: For very large values of capacitance measurement time can be

several minutes before the final reading stabilizes.

Frequency Measurements

1. Set the function switch to the V Hz Position.

2. Press and hold the MODE button to select the Frequency (Hz)
function. “k Hz” will appear in the display.

3. Insert the black test lead banana plug into the negative COM jack
and the red test lead banana plug into the Hz positive jack.

4. Touch the test probe tips across the part under test.

5. Read the Frequency value on the display.

6. The display will indicate the proper decimal point and value.

7. Press and hold the MODE button again to return to the voltage mode

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CAP

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Type K Temperature Measurements

1. Set the function switch to the K Temp position.

2. Insert the Temperature Probe into the negative COM and the
positive TEMP jacks, observing polarity.

3. Touch the Temperature Probe tip to the device under test.
Continue to touch the part under test with the probe until the
reading stabilizes.

4. Read the temperature on the display. The digital reading will
indicate the proper decimal point and value.

WARNING: To avoid electric shock, be sure the thermocouple probe has
been removed before changing to another measurement function.

Note: An open input or a temperature overrange the meter will display

“OL” and beep.

Note: See the “Temperature Units” paragraph to select °F or °C
Note: The temperature range of the supplied thermocouple probe is -20 to 250°C (-4 to

482°F)

Continuity Measurements

1. Insert the black test lead into the negative COM terminal and the red test lead into the

Ω positive terminal.

2. Set the function switch to the

3. Use the MODE button to select continuity
MODE button is pressed.

4. Touch the test probe tips across the circuit or component under test.

5. If the resistance is < 40Ω, a tone will sound.

•))) position.

•))). The display icons will change when the

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 jack

2. Turn the function switch to position. Use the MODE button to select the diode
function if necessary (diode symbol will appear on the LCD when in Diode test mode)

3. Touch the test probe tips to the diode or semiconductor junction under test. Note the
meter reading

4. Reverse the test lead polarity by reversing the red and black leads. Note this reading

5. The diode or junction can be evaluated as follows:

 If one reading displays a value (typically 0.400V to 0.900V) and the other

reading displays OL, the diode is good.

 If both readings display OL the device is open.
 If both readings are very small or ‘0’, the device is shorted.

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Non-Contact InfraRed Temperature Measurement s

1. Set the function switch to the IR Temp position.

2. Aim the infrared sensor (rear of the meter) at the
surface to be measured.

3. Press the
function switch to turn on the laser pointer and
identify the surface spot to be measured.

4. The area of the surface to be measured must be
larger than the spot size as determined by the
distance to spot size specification.

5. Read the temperature in the display.

Note: See the “Temperature Units” paragraph to select

WARNING: Do not directly view or direct the laser pointer at
an eye. Low power visible lasers do not normally present a

hazard, but may present some potential for hazard if viewed
directly for extended periods of time.

IR Spot to Distance Diagram
The 8:1 spot to distance ratio determines the size of the measured surface area with

respect to the distance the meter is held away from the surface.

button in the center of the rotary

Diameter of spot

1.25cm

2.5cm

10cm

20cm

60cm

Distance to object

o

F or oC

7.5cm

IR Measurement Notes

1. The object under test should be larger than the spot (target) size calculated by the
field of view diagram.

2. If the surface of the object under test is covered with frost, oil, grime, etc., clean
before taking measurements.

3. If an object's surface is highly reflective, apply masking tape or flat black paint to the
surface before measuring.

4. The meter may not make accurate measurements through transparent surfaces such
as glass.

5. Steam, dust, smoke, etc. can obscure measurements.

6. To find a hot spot, aim the meter outside the area of interest then scan across (in an
up and down motion) until the hot spot is located.

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Data Hold

To freeze the LCD reading, press the HOLD button. While data hold is active, the HOLD
icon appears on the LCD. Press the HOLD button again to return to normal operation.

Peak Hold

The Peak Hold function captures the peak AC or DC voltage or current. The meter can
capture negative or positive peaks as fast as 1 millisecond in duration.

1. Turn the function switch to the A or V position.

2. Use the MODE button to select AC or DC

3. Allow time for the display to stabilize.

4. Press and Hold the PEAK button until “CAL” appears in the display. This procedure
will zero the range selected.

5. Press the PEAK button, Pmax will display.

6. The display will update each time a higher positive peak occurs.

7. Press the PEAK button again, Pmin will display. The display will now update and
indicate the lowest negative peak.

8. To return to normal operation, press and hold the PEAK button until the Pmin or

Pmax indicator switches off.

Note: If the Function switch position is changed after a calibration the Peak Hold

calibration must be repeated for the new function selected.

MAX/MIN

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 and “MIN” will appear 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. Press the MAX/MIN key and a blinking “MAX MIN” will appear. The meter will display
the present reading, but will continue to update and store the max and min readings.

4. To exit MAX/MIN mode press and hold the MAX/MIN key for 2 seconds.

Temperature Units (˚F / ˚C)

The temperature units selection switch is located in the battery
compartment. To change the units, remove the battery door, lift
out the battery and set the switch for the desired units.

Units Switch

F

C

LCD Backlight Button

The LCD is equipped with backlighting for easier viewing,
especially in dimly lit areas. Press the backlight button to turn the
backlight on. Press again to turn the backlight off.

Automatic Power OFF

In order to conserve battery life, the meter will automatically turn off after approximately 25
minutes. To turn the meter on again, turn the function switch to the OFF position and then
to the desired function position.

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Maintenance

WARNING: To avoid electrical shock, disconnect the meter from any circuit, remove the
test leads from the input terminals, and turn OFF the meter before opening the case. Do
not operate the meter with an open case.

Cleaning and Storage

Periodically wipe the case with a damp cloth and mild detergent; do not use abrasives or
solvents. If the meter is not to be used for 60 days or more, remove the battery and store it
separately.

Battery Replacement

1. Remove the Phillips head screw that secures the rear battery door

2. Open the battery compartment

3. Replace the 9V battery

4. Secure the battery compartment

You, as the end user, are legally bound (EU Battery ordinance) to return all
used batteries, disposal in the household garbage is prohibited! You can
hand over your used batteries / accumulators at collection points in your
community or wherever batteries / accumulators are sold!

Disposal: Follow the valid legal stipulations in respect of the disposal of the
device at the end of its lifecycle

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Specifications

Function Range & Resolution Accuracy (% of reading + digits)
AC Current

50/60 Hz

DC Current

AC Voltage

50/60Hz

DC Voltage

Resistance

Capacitance

Frequency

400.0 AAC ± (2.5% + 8d)
1000 AAC ± (2.8% + 5d)

400.0 ADC ± (2.5% + 5d)
1000 ADC ± (2.8% + 5d)

400.0 mVAC ± (1.0% + 10d)

4.000 VAC
± (1.5% + 5d) 40.00 VAC

400.0 VAC

1000 VAC ± (2.0% + 5d)

400.0 mVDC ± (0.8% + 2d)

4.000 VDC
± (1.5% + 2d) 40.00 VDC

400.0 VDC

1000 VDC ± (2.0% + 2d)

400.0Ω

4.000kΩ

40.000kΩ

400.0kΩ

4.000MΩ

40.00MΩ

4.000nF ± (5.0% + 30d)

40.00nF ± (5.0% + 20d)

400.0nF

40.00µF

400.0µF ± (4.0% + 10d)

4.000mF ± (10% + 10d)

40.00mF unspecified

4.000kHz ± (1.5% + 2d)

Sensitivity: 100V (<50Hz); 50V (50 to 400Hz); 5V (401Hz to 4000Hz)

± (1.0% + 4d)

± (1.5% + 2d)

± (2.5% + 3d)
± (3.5% + 5d)

± (3.0% + 5d) 4.000µF

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Function Range and Resolution Accuracy (% of reading + digits)
Temperature

(type-K)
Temp

(IR)

-4 to 1400oF ± (3%rdg + 9oF)

-20 to 760oC ± (3%rdg + 5oC)

-58 to -4°F ± 9 °F

-4 to 518°F

-50 to -20°C ±5°C

-20 to 270°C

±2.0% reading or ± 4°F

whichever is >

±2.0% reading or ±2°C

whichever is >

Clamp jaw opening 43mm (1.7") approx.
Display 3-3/4 digits (4000 counts) backlit LCD
Continuity check Threshold 40Ω; Test current < 0.5mA
Diode test Test current of 0.3mA typical;
Open circuit voltage < 3VDC typical
Low Battery indication Battery symbol is displayed
Over-range indication ‘OL’ display
Measurement rate 2 readings per second, nominal
PEAK Captures peaks >1ms
Thermocouple sensor Type K thermocouple required
IR Spectral response 6 to 16µm
IR Emissivity 0.95 fixed
IR distance ratio 8:1
Input Impedance 10MΩ (VDC and VAC)
AC bandwidth 50 to 400Hz (AAC and VAC)
AC response True rms (AAC and VAC)
Crest Factor 3.0 in 40A and 400A ranges, 1.4 in 1000A range (50/60Hz

and 5% to 100% of range)

Operating Temperature 5°C to 40°C (41°F to 104°F)
Storage Temperature -20°C to 60°C (-4°F to 140°F)
Operating Humidity Max 80% up to 31°C (87°F) decreasing linearly to 50% at

40°C (104°F)

Storage Humidity <80%
Operating Altitude 2000meters (7000ft) maximum.
Battery One (1) 9V Battery (NEDA 1604)
Auto power OFF After approx. 25 minutes
Dimensions & Weight 270x110 x50mm (10.6x4.3x2”); 386g (13.6 oz)
Safety For indoor use and in accordance with the requirements for

double insulation to IEC1010-1 (2001): EN61010-1 (2001)
Overvoltage Category IV 600V and Category III 1000V,
Pollution Degree 2.

Patent notice U.S. Patent 7163336

Copyright © 2010 Extech Instruments Corporation (a FLIR company)

All rights reserved including the right of reproduction in whole or in part in any form.

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