Extech Instruments EX840-NIST, EX840 User manual

User's Guide

Extech EX840 True RMS 1000 Amp
Clamp Meter with IR Thermometer

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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, 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)

 Ohms (Resistance)

A Amperes (Current)

F Farad (Capacitance)

Hz Hertz (Frequency)

o

F and oC Fahrenheit and Celsius units (Temperature)

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

)

)



) Continuity test

Current

Diode test

Laser pointer

3

5

6

9

10

1

11

2

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
range

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 andr
emoved 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 or ADC

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  positive terminal.

2. Set the function switch to the 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 before

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.

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

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.

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

Ù

CAP

Hz

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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 
positive terminal.

2. Set the function switch to the

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

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

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

))) position.

))). The display icons will change when the MODE

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 Measurements

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
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 function

o

F or oC

Diameter of spot

1.25cm

2.5cm

10cm

20cm

60cm

Distance to object

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)

400.0

4.000k

40.000k

400.0k

4.000M

40.00M

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 1400

-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

o

F ± (3%rdg + 9oF)

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 40; 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 10M (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 270x110x50mm (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

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