DIGITAL CLAMP METER

21-S
Safety Statement 1
Safety Symbols 4
Overview 5
Instrument panel description 5
Function button: 6
Measurement Operation 6
Power on/off 7
Maximum/minimum value measurement 7
Flashlight on/off 8
Data hold 8
Auto Power off 8
Cancel Auto Power off 8
SMART measurement mode 9
Professional measurement mode 10
AC/DC current measurement 10
AC inrush current measurement 11
AC/DC voltage measurement 12
Resistance measurement 13
Continuity test 13
Diode test 14
AC/DC mV measurement 15
 Frequency/duty measurement 16
Capacitance measurement 16
Temperature measurement 17
Non-contact AC Voltage Detection (NCV) 18
Single probe live wire detection (LIVE) 19
General Technical Specifications 20
Accuracy Specifications 21
DC voltage 21
AC voltage 22
DC current 22
AC current 22
Resistance 23
Continuity 23
Diode 24
Capacitance 24
Frequency/Duty 25
Temperature 26
Maintenance 26
General maintenance 27
Battery Installation or Replacement 27
 SAFETY STATEMENT
Warning
Read this manual before using the instrument.
“ Warning” mark indicates the condition and operation
which may cause danger to users.
“ Caution” mark refers to the condition and operation
which may cause damage to the instrument or
equipment.
Warning
In order to avoid possible electric shock or personal
injury and other safety accidents, please abide by the
following specifications:
• Please read this manual carefully before using the
instrument, and pay special attention to safety
warning information.
• Strictly observe the operation of this manual and
use this instrument. Otherwise, the protection
function of the instrument may be damaged or
weakened.
• Please be careful if the measurement exceeds 30V
AC true RMS, 42V AC peak or 60V DC. There may
be danger of electric shock at this kind of voltage.
• Voltage applied between terminals or between

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 each terminal and grounding point shall not
exceed the rated value.
• By measuring the known voltage to check whether
the meter work is normal, if it is not normal or
damaged, do not use it again.
• Before using the instrument, please check whether
there are cracks in the instrument shell or plastic
parts damaged. If so, please do not use again.
• Before using the instrument, please check whether
the probe is cracked or damaged. If so, please
replace the same type and the same electrical
specifications.
• Do not exceed the lowest rated Category of
Measurement (CAT) rating in products, probes or
accessories.
• Do not measure the current when the probe is
inserted into the input jack.
• Don't work alone.
• Please comply with local and national safety code.
Wear personal protection equipment (such as
approved rubber gloves, masks and flame
retardant clothes, etc.) to prevent being damaged
by electric shock and electric arc due to exposed
hazardous live conductor.
• When it shows low battery indicator, please

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 replace the battery in time in case of any
measurement error.
• Do not use the instrument around explosive gas,
steam or in wet environment.
• When using the probe, please put your fingers
behind the finger protector of the probe.
• When measuring, please connect the neutral wire
or the ground wire firstly, then connect the live
wire; When disconnecting, please disconnect the
live wire firstly, then disconnect the neutral wire
and ground wire.
• Before opening the outer cabinet or battery cover,
please remove the probe on the instrument. Do
not use the instrument in the circumstances that
the instrument is taken apart or battery cover is
opened.
• It only meets the safety standards when the
instrument is used together with the supplied
probe. If the probe is damaged and needs to
replace, the probe with same model number and
same electrical specifications must be used for
replacement.

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High voltage warning

AC (Alternating current)

DC (Direct current)

AC or DC

Warning, important safety signs

Ground

Equipment with double insulation /

reinforced insulation protection

Low battery

Product complies with all relevant

European laws

Inrush current measurement

The additional product label shows that

do not discard this electrical/electronic
product into household garbage.

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Overview
A new generation of true RMS high performance
intelligent digital clamp meters that combine a wide
range of functions to make your work easier, more
efficient and safer.
It is capable of measuring AC/DC voltage, AC/DC current,
inrush current, frequency, duty cycle, resistance,
capacitance, temperature, diode, continuity, NCV and
more.
Instrument panel description
1 CV probe
2 Clamp
3 Flashlight
4 Alarm Indicator LED
5 Trigger
6 Display screen
7 Function button
8 Black meter pen socket
9 Red meter pen socket
10 Power button
11 Data hold/Flashlight key

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Function button:
Gear function selection/intelligent measurement
button
Maximum/Minimum Value button
Function selection/inrush current measurement
button

Measurement Operation
Warning
• Do not measure voltages above 600V as this may
damage the meter.
• When measuring high voltage, pay special attention
to safety, so as not to be subjected to electric shock
or personal injury.
• Before use, test known voltages or currents with the
meter to confirm that the meter is fully functional.

Power on/off
1) Press and hold the key for about 2 seconds to
turn on.
2) The meter automatically performs a self-test when
switched on and displays "CAL", do not press the
trigger to open the clamp at this time.
3) Until the buzzer beeps "beep, beep, beep" to
indicate the completion of the self-test.

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4) The meter is only available for measurement.
5) When the measurement is finished, press and hold
the key for about 2 seconds to switch off the
meter.

Maximum/minimum value measurement

1) Press button to switch on the maximum and
minimum value measurement.
2) Press button again to cycle through the
maximum and minimum values.
3) Press the button and hold it for more than 2
seconds to exit the maximum and minimum
measurement.
Note: This function does not work with inrush current,
continuity, diode, frequency/duty cycle, temperature,
NCV/Live functions.

Flashlight on/off
Press the button and hold for more than 2 seconds
to turn the flashlight on or off.

Data hold
Press the button to enable or disable the data
hold function.

Auto Power off

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 If there is no operation within 15 minutes after
starting up, the meter will automatically shut down
to save battery energy.

Cancel Auto Power off

1) Press and hold the key, then press the key to turn
on the instrument power and then release the
key, the display will have no " " symbol and the
automatic switch-off function will be cancelled.
2) Restart the machine to restore the automatic
shutdown function. The display displays the " "
symbol.
Note: After the automatic shutdown function is disabled,
you need to manually power off the meter.

SMART measurement mode

The meter enters smart mode by default. Can measure AC
and DC voltage, AC and DC current, resistance,
continuity, the instrument automatically identify the
measurement signal.
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Don't need to select the measurement function,
directly measure the AC/DC voltage, AC/DC current,

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 resistance, continuity, the instrument automatically
identify and measure. The current is measured with
the clamp, and the other measurements are taken
from the pen input.
3) Read the measurement results from the display
screen. The frequency is displayed when the AC
signal is measured.
Note1 : Minimum identifiable DC current 0.8A.
: Minimum identifiable AC current 0.5A.
: Minimum identifiable AC/DC voltage 0.8V.
Note2 Automatic identification priority: resistance, DC
voltage, AC voltage, DC current, AC current.

Professional measurement mode

AC/DC current measurement
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to "A", and press
the button to select AC or DC current
measurement function.
3) In the DC current measurement function, if the
display is not zero when the instrument is not

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 measuring, press and hold the " " key to clear zero,
display "ZERO" and then measure.
4) Then press the trigger to open the clamp, clamp the
conductor to be tested, slowly release the trigger until
the clamp are completely closed, and determine
whether the conductor to be tested is clamped in the
center of the pliers, if the conductor is not in the
center of the pliers, additional errors will occur.
5) Read the measurement results from the display
screen. The frequency is also shown on the display
when measuring AC current.
Note: AC clamp meter without DC current measurement
function; AC/DC clamp meter with this function

AC inrush current measurement

1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to "A", and press the
button to select inrush current measurement
function and display the symbol "INRUSH".
3) Then press the trigger to open the clamp, clamp the
conductor to be tested, slowly release the trigger until
the clamp are completely closed, and determine

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 whether the conductor to be tested is clamped in the
center of the pliers, if the conductor is not in the
center of the pliers, additional errors will occur.
4) Turn on the device to be tested (such as the motor)
and then trigger the measurement by the surge
current.
5) Read the measurement results from the display
screen.
Note: The measuring range of inrush current is 5~600A.

AC/DC voltage measurement

1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to "V", and press the
button to select AC or DC voltage measurement
function.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Contact the probe to the measured circuit (connect to
the measured power supply or circuit in parallel).
5) Read the measurement result on the screen. When
the AC voltage is measured, the frequency is
displayed on the display screen.

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Resistance measurement
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the "Ω" position.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Contact the probe to the measured circuit or
resistance.
5) Read the measurement result on the screen.
Continuity test
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the " " position.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Contact the probe to the measured circuit or
resistance.
5) If the resistance or circuit of the measured resistance
is less than 50Ω, the buzzer sounds and the alarm

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 indicator light is green, the screen displays the
resistance.

Diode test
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the " " position.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Touch the diode anode with the red probe, the black
probe contacts the diode cathode.
5) Read the measurement result on the screen.
6) If the probe polarity is opposite to the diode polarity,
the meter shows "OL", which can be used to
distinguish the anode and cathode.

AC/DC mV measurement
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent measurement
mode.
2) Press button, set the pointer to "mV", and press
the button to select AC or DC voltage measurement

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 function.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Connect the meter in parallel to the power supply or
load to be tested.
5) Read the measurement result on the screen. When
the AC voltage is measured, the frequency is
displayed on the display screen.

Frequency/duty measurement
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the "Hz/%"
position.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Connect the meter in parallel to the power supply or
load to be tested.
5) Read the measurement result on the screen.

Capacitance measurement
1) Press the button to turn on the power supply of

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 the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the " " position.
3) Insert the red probe in “INPUT” jack, insert the black
probe in “COM” jack.
4) Contact the probe to the measured circuit or
Capacitance.
5) Read the measurement results from the display
screen after the display is stable.
Note: The stability time of large capacitance is relatively
long

Temperature measurement
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the meter
will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the " " position.
3) Insert the K-type thermocouple into the instrument,
the positive pole (red) of the thermocouple into the
“INPUT” jack, and the negative pole (black) into the
“COM” input.
4) Contact the thermocouple probe with the measured
object and read the results from the display screen.

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 Warning
When measuring temperature with thermocouple, the
probe of thermocouple can't touch the charged object,
otherwise it may damage the instrument and may suffer
electric shock or personal injury.

Note :
It takes a long time for the cold end of thermocouple to
be restored in the instrument to achieve thermal balance
with the environment.

Non-contact AC Voltage Detection (NCV)

1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the
meter will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to the "NCV/Live"
position.
3) Then NCV probe gradually approaches the detected
point.
4) When the weak electric field signal is induced, the "-
-L" symbol will be displayed, the beep will emit a
slow beep sound, and the green LED indicator will
light up.
5) When the strong electric field signal is induced, the

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 "--H" symbol will be displayed, the beep will emit
a fast beep sound, and the red LED indicator will
light up.
Note: Before using the NCV function, remove the
stylus. Otherwise, the detection accuracy will be
affected.
Single probe live wire detection (LIVE)
1) Press the button to turn on the power supply of
the meter. After the self-test is completed, the
meter will display and enter the intelligent
measurement mode.
2) Press button, set the pointer to "NCV/Live"
position, and press the button to select "Live"
measurement function.
3) Insert the red probe into the "INPUT" jack and
remove the black probe.
4) Contact the red probe with the conductor under
test
5) When a low voltage is detected the character "---L"
is displayed, the beeper emits a slow beeping tone
and the green LED lights up.
6) When a high voltage is detected, the "--H" character
is displayed, the buzzer emits a fast beeping sound,
and the red LED indicator lights up. Under normal
circumstances, the detected line is "LIVE" line at this

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 time.
General Technical Specifications
• Environment condition of using:
CAT.III 600V
Pollution level ±2
Altitude < 2000m
Working environment temperature and
humidity: 0~40°C (<80% RH, <10°C non-
condensing).
Storage environment temperature and
humidity: -10~60°C (<70% RH, remove the
battery).
• Temperature coefficient:
0.1x accuracy/°C (<18°C or >28°C).
• MAX. Voltage between terminals and earth
ground：600V
• Display: 6000 counter readout. Automatically
display the unit symbols according to the shift of
the measurement function.
• Over range indication: it displays “OL”.
• Low battery indication: when the battery voltage is
lower than the normal working voltage, “ ” will
be displayed.

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• Input polarity indication: automatically display
“__”.
• Power: 3 x 1.5V AAA batteries.

Accuracy Specifications
The accuracy applies within one year after the
calibration.
Reference condition: the environment temperature
18°C to 28°C, the relative humidity is no more than 80%
accuracy: ±（ reading + word）

DC voltage
Range Resolution Accuracy
600mV 0.1mV
6V 0.001V
± (0.5%reading+5)
60V 0.01V
600V 0.1V
Input impedance : 10MΩ. Maximum input voltage: 600V

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AC voltage
Range Resolution Accuracy
600mV 0.1mV
6V 0.001V
± (0.8%reading+5)
60V 0.01V
600V 0.1V
Input impedance : 10MÙ Maximum input voltage: 600V.
Frequency Response : 40Hz ~ 1kHz(TRMS).
DC current
Range Resolution Accuracy
60A 0.01A
± (2.5% reading +5)
600A 0.1A
Maximum input current: 600A.
AC clamp meter without DC current function.

AC current
Range Resolution Accuracy
50~60Hz : ± (2.5%reading + 5)
60A 0.01A Other : ± (3.0%reading + 10)
Inrush current :
600A 0.1A ± (5.0%reading+10)
Maximum input current: 600A.
Frequency Response : 40Hz ~ 400Hz(TRMS).

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Resistance
Range Resolution Accuracy
600Ω 0.1Ω
6kΩ 0.001kΩ
60kΩ 0.01kΩ
± (1% reading +5)
600kΩ 0.1kΩ
6MΩ 0.001MΩ
60MΩ 0.01MΩ

Continuity
<50Ù, the buzzer Test Voltage Approx.
sounds and the green 1V Overload protection :
indicator LED on. 250V

Diode
It displays the Reverse DC voltage is
approximate forward about 3V
voltage value of the Overload protection:
diode. 250V

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Capacitance
Range Resolution Accuracy
6nF 0.001nF
60nF 0.01nF
600nF 0.1nF
6µF 0.001µF
± (4.0% reading +5)
60µF 0.01µF
600µF 0.1µF
6mF 0.001mF
60mF 0.01mF
Overload protection: 250V.
The above accuracy does not include the error caused
by the pen capacitance.
Frequency/Duty
Range Resolution Accuracy
100Hz 0.01Hz
1000Hz 0.1Hz
10kHz 0.001kHz ±(1.0%reading+3)
100kHz 0.01kHz
1000kHz 0.1kHz
10MHz 0.001MHz
±(3.0%reading+3)
1~99% 0.1%

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Overload protection: 250V.
The "mV" gear voltage measurement frequency :
1) Range: 10Hz ~ 2 kHz
2) Sensitivity of signal: >50mV(RMS), sine wave
The "V" gear voltage measurement frequency :
1) Range: 10Hz ~ 2 kHz
2) Sensitivity of signal: >0.5V(RMS), sine wave
The current measurement frequency :
1) Range:10Hz ~ 2 kHz
2) Sensitivity of signal: >12A(RMS), sine wave

The "Hz/%" gear :

1) Frequency range: 5Hz ~ 10MHz
2) Voltage range: >2.5V RMS (The higher the
frequency, the higher the voltage)
Temperature
Unit Resolution Accuracy
-40ºC~ 10ºC ± 3℃
ºC 1ºC 10ºC ~ 100ºC ± 2℃
100ºC ~ 1000ºC ± 2.0%
-40ºF~50ºF ± 6℉
50ºF~ 212ºF ± 4℉
ºF 1ºF 212ºF~ 1832ºF ± 2.0%
Note: The above accuracy does not include the error of
thermocouple probe.

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Maintenance
Warning
To avoid electric shock, remove the test probe
before opening the battery cover or back cover

General maintenance
• Maintenance and service of this instrument must
be carried out by professional qualified
maintenance personnel or maintenance
department.
• Use wet cloth or mild detergent regularly to clean
the shell. Do not use abrasives or solvents. Wipe
the contacts in the socket with a clean cotton
swab soaked in alcohol.

Battery Installation or Replacement

The meter uses three AAA 1.5V batteries. Please install
or replace the batteries according to the following
steps.
1) Turn off the power of the instrument and remove
the probe
2) Use screwdriver to unscrew the screw that fixes the
battery cover and remove the battery cover.

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3) Remove the old battery and install the new battery
according to the polarity of the battery marked in
the battery box.
4) After installing the new battery, cover the battery
cover and lock the screw.

Warning
• To avoid the possibility of electric shock or personal
injury caused by incorrect reading, replace the
battery immediately when the " " sign is displayed
on the display screen.
• Please use the same type of batteries, do not use
substandard batteries.
• In order to ensure safe operation and maintenance
of the instrument, please take out the battery when
not in use for a long time, in order to prevent
damage to the product caused by battery leakage.

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