Owon CM240 User manual

Digital Clamp Meter
User Manual
CM240
WWW.OWON.COM.CN

Mar. 2016 edition V1.2
Copyright © LILLIPUT Company. All rights reserved.
The LILLIPUT's products are under the protection of the patent rights, including ones which have already
obtained the patent rights and those which are applying for. The information in this manual will replace all
that in the materials published originally.
The information in this manual was correct at the time of printing. However, LILLIPUT will continue to
improve products and reserves the rights to change specification at any time without notice.
is the registered trademark of the LILLIPUT Company.
Fujian LILLIPUT Optoelectronics Technology Co., Ltd.
No. 19, Heming Road
Lantian Industrial Zone, Zhangzhou 363005 P.R. China
Tel: [phone] Fax: [phone]
Web: www.owon.com.cn E-mail: [e-mail]

i
Table of Contents
Instruction ..................................................... 1
Check the Accessories ................................... 1
Safety Information.........................................1
Electrical Symbols..........................................3
Front Panel Description ................................. 3
LCD Display Symbols......................................4
Button Function and Auto Power Off ............4
Making Measurements..................................5
Measuring DC Voltage ................................................... 5
Measuring AC Voltage..................................................... 6
Measuring Resistance.................................................... 7
Testing Diode .................................................................. 7
Testing Continuity ........................................................... 8
Measuring AC Current.................................................... 9
General Specifications...................................9
Electrical Specifications ...............................10
Replacing the Batteries................................12

1
Instruction
Instruction
CM240 digital clamp meter is a
1
32
- digit LCD multi-meter with
steady operations, fashionable structure and highly reliable
measuring instrument. The meter uses large scale of
integrated circuit with double integrated A/D converter as its
core and has full range overload protection. The meter can
perform measurements of AC and DC voltage, AC current,
resistance, diode and continuity test.
Warning
To avoid electric shock or personal injury, read the “Safety
Information" and "Safety Warning" carefully before using
the meter.
Check the Accessories
Open the package case and take out the Meter. Check
the following items carefully to see any missing or
damaged part:
Item
Description
Quantity
1
User Manual
1 piece
2
Test Lead
1 pair
In the event you find any missing or damage, please
contact your dealer immediately.
Safety Information
Thisdigitalclampmeterhasbeendesignedaccordingsafety
standard IEC-61010-I and LECI010-2-032 concerning
electronic
measuring instruments with an over voltage
category (CAT II 600V) and pollution degree 2.
Safety Warning

2
Safety Information
1. Read the operating instructions before using the instrument
and pay particular attention to all WARNINGS and
CAUTIONS in this instruction manual.
2. Be sure that the cover and the test leads of the meter are in
good conditions.
3. Set the range / function switch at the correct position when
measuring.
4. Make sure to insert the red and the black test leads to their
appropriate jacks. The black test lead should be connected
first when measuring while the red test lead should be
disconnected first after measuring.
5. When the range and function changes, both test leads
should be disconnected.
6. To avoid damage to the instrument, never exceed the
allowable maximum input of each range.
7. Be care of electric shock hazard when the voltage to be
tested is above DC 60V or AC 30V.
8. To avoid electric shock, do not open the battery
compartment cover when making measurement.
9. Remove the test leads from the circuit being measured
before replacing the battery.
10. Do not change the built-in circuit to avoid damage to the
meter.
11. Do not use or store the instrument in an explosive
atmosphere (i.e. the presence of flammable gas or fume,
vapor or dust).
12. CAT II-Measurement Category II is for measurements
performed on circuits directly connected to low voltage
installation.CExamples are measurements on household
appliances, portable tools and similar equipments.)Dot not
use the meter for measurements within Measurement
Categories III and IV.

3
Electrical Symbols
Electrical Symbols
Warning
Earth
Ground
Double
insulated
(Protection
classII )
Alternating
signal test
Direct
signal
test
Continuity
buzzer
Diode test
Low Battery
AC or DC
Conforms to European Union directives
Application around and removal from
HAZARDOUS LIVE conductors is permitted.
Capacitor
Front Panel Description
1. Input Terminals
2. LCD Display
3. Functional Buttons (SEL/MAX/HOLD )
4. Rotary Switch
5. Trigger: press the lever to open the
transformer jaw.
6. Hand Guards: to protect user's hand
from touching the dangerous area.
7. Transformer Jaw: designed to pick up
the AC and DC current flowing through
the conductor. It could transfer current
to voltage. The tested conductor must
vertically go through the Jaw center.

4
LCD Display Symbols
LCD Display Symbols
1. Alternating signal test
2. Direct signal test
3. Low Battery
4. Auto range mode
5. Diode test
6. Continuity buzzer
7. The maximum value is
being measured
8. This indicates that the
display data is being held
9. Ohms, kilo-ohms, mega-ohms resistance test
10. Amperes (current)
11. Milli-volts, volts (voltage)
12. Negative polar mark
13. "OL": The input value is too large for the selected range.
Button Function and Auto Power Off
1. H: For measuring data hold, press the H button, the peak value
of current data will be keeping displaying on LCD; press it again
to cancel this function.
2. MAX: Maximum data hold button, when press this button, the
A/D converter will keep measuring, and the display updating the
data and hold the maximum data.
3. SEL: Function selection button, press for switching
ohm/diode/continuity function when tested objects change.
4. Auto-power off : If there is no any operation within any fifteen
minutes after power is on, the meter will auto power off. Turn the
rotary switch or press any function button to resume operation of
the meter under the auto power off mode. At the same time
when power on, if press the "H" button, auto power off will be
disabled.

5
Making Measurements
Note:
After automatic turn-off, then press Hto re-start, the function of
automatic turn-off will be cancel.
5. Buzzer
Set the selector to any measuring function (except 2/20A ACV
function), press any button, the buzzer will sound; otherwise,
the button is idleness. One minutes before auto power off, the
buzzer continue sound in five times, and one long buzz before
power off.
Note: when the selector in measuring function of 2/20A ACV,
the buzzer won’t sound.
6. The Effectiveness of Functional Buttons
Not every functional buttons can be used on every rotary switch
positions. Below table describe which functional buttons can be
used on which rotary switch positions.
Range Functional Buttons
LIGHT
SEL
H
MAX
RAN
DC Voltage
●
N/A
●
●
●
AC Voltage
●
N/A
●●
●
Resistance ●N/A ●N/A ●
Continuity, Diode test ●●●N/A N/A
DC current 2/20A
●
N/A
●●●
AC current 200/400A
●
N/A
●
●
●
Making Measurements
Measuring DC Voltage
WARNING
Beware of Electrocution
Pay special attention to avoid electric shock when
measuring high voltage.
Do not input the voltage which more than 600V DC.

6
Making Measurements
1) Plug the black test lead into
the COM jack and the red test
lead into the INPUT Jack.
2) Set the rotary switch to V
position to make the meter get
into DC V range.
3) Connect the test leads to the
voltage source or load
terminals for measurement.
4) Take the reading on the LCD.
When DC voltage measurement has been completed,
disconnect the connection between the testing leads and the
circuit under test and remove testing leads from the input
terminals.
Measuring AC Voltage
WARNING
Beware of Electrocution
Pay special attention to avoid electric shock when
measuring high voltage. Do not input the voltage which
more than 600V rms AC.
1) Plug the black test lead into
the COM jack and the red
test lead into the INPUT
Jack.
2) Set the rotary switch to V~
position to make the meter
get into AC V range.
3) Connect the test leads to
the voltage source or load
terminals for measurement.
4) Take the reading on the LCD.
When AC voltage measurement has been completed, disconnect
the connection between the testing leads and the circuit under test

7
Making Measurements
and remove testing leads from the input terminals.
Measuring Resistance
WARNING
To avoid possible damage to your multimeter or to the
equipment under test, disconnect the circuit power and
discharge all high-voltage capacitors before measuring
resistance.
1) Plug the black test lead into
the COM jack and the red
test lead into the INPUT Jack.
2) Set the rotary switch to
Ω/ / range position.
3) Connect the test leads to the
ends of the resistance or
circuit for measurement.
4) Take the reading on the LCD.
To obtain a more precise
reading, you could remove the objects being tested from the circuit
when measuring.
Testing Diode
WARNING
To avoid possible damage to your multimeter or to the
equipment under test, disconnect the circuit power and
discharge all high-voltage capacitors before testing diodes.

8
Making Measurements
1) Plug the black test lead into
the COM jack and the red
test lead into the INPUT Jack.
2) Set the rotary switch to
Ω/ / range position.
3) Press the "SEL" button to
switch to test.
4) Connect the red test leads to
the anode and the black test
lead to the cathode of the
diode for testing.
5) Take the reading on the LCD.
To obtain a more precise reading, you could remove the objects
being tested from the circuit when measuring.
Testing Continuity
WARNING
To avoid possible damage to your multimeter or to the
equipment under test, disconnect the circuit power and
discharge all high-voltage capacitors before testing for continuity.
1) Plug the black test lead into
the COM jack and the red
test lead into the INPUT Jack.
2) Set the rotary switch to
Ω/ / range position.
3) Press the "SEL" button to
switch to continuity test.
4) Connect the test leads to the
ends of the resistance or
circuit for measurement.
The buzzer sounds if the resistance of a circuit under test is less
than 30Ω.

9
General Specifications
A
~
A
~
The buzzer may or may not sounds if the resistance of a circuit
under test is between 30Ω to 100Ω.
The buzzer does not sound if the resistance of a circuit under test
is higher than 100Ω.
Measuring AC Current
WARNING
Beware of Electrocution.
Ensure that the test leads are disconnected from the meter
before making current clamp measurements.
1) Set the rotary switch to the 2/20
or 200/400 range position.
2) Press the trigger to open jaw. Fully
enclose only one conductor.
3) Take the reading on the LCD.
Note:
For right results, do not enclose
more than one conductor in the jaw.
For optimum results, center the
conductor in the jaw.
General Specifications
1. Auto range and manual range options are available.
2. Over range protection is provided for all ranges.
3. Display:
1
32
- digit (1999 count)
4. Measuring method: Dual slope integration A/D converter
5. Sampling speed: 3 time/sec
6. Unit display: Function and unit symbols displayed
7. Polarity: Automatic negative polarity display
8. Overload indication: Symbol "OL" appears on the LCD
9. Low battery indication: Symbol appears on the LCD

10
Electrical Specifications
10. Auto power off time: 15 min
11. Operation temperature: 0 to 30℃(≦75%RH), 30℃to 40℃
(≦70%RH), 40℃to 50℃(≦40%RH)
12. Storage temperature: -20℃to 60℃, ≦75%RH
13. Operation power: Two 1.5V, AAA batteries
14. Dimension: 65mm(W) x 177mm(L) x 28mm(D)
15. Weight: 186g
Electrical Specifications
Accuracy: ± (%reading + digits)
Operation temperature: 23℃, ≦75%RH
1.
AC Voltage : Auto Range
Range
Resolution
Accuracy
Overload protection
2 V
1 mV
± (1.2%+5d)
600V rms
20 V
10 mV
200 V
100 mV
600 V
1 V
± (1.5%+5d
)
Input impedance: 10 MΩ
Frequency range: 40 Hz –1 kHz
2. DC Voltage: Auto Range
Range
Resolution
Accuracy
Overload protection
200 mV
0.1 mV
± (0.8%+5d
)
600V rms
2 V
1 mV
± (0.8%+5d)
20 V
10 mV
200 V
100 mV
600 V
1 V
± (1.0%+5d
)
Input impedance : 10 MΩ

11
Electrical Specifications
3.
Resistance : Auto Range
Range
Resolution
Accuracy
Overload protection
200.0 Ω
100 mΩ
± (1.2%+5d
)
600 Vp
2.000 kΩ
1 Ω
± (1%+3d)
20.00 kΩ
10 Ω
200.0 kΩ
100 Ω
2.000 MΩ
1 kΩ
± (1.2%+5d
)
20.00 MΩ
10 kΩ
± (1.5%+5d
)
4. Continuity
:
Range
Resoluti on
Accuracy
Overload
protection
100 mΩ
Built-in buzzer will sound, if
resistance is lower than
≦30Ω (Open circuit voltage
is about 0.45V)
600 Vp
Note:
The buzzer may or may not sounds if the resistance of a circuit
under test is between 30Ω to 100Ω.
The buzzer does not sound if the resistance of a circuit under test
is higher than 100Ω.
5. Diode:
Range
Resolution
Accuracy
Overload
protection
1 mV
Displaying approximate
forward voltage of diode
(Open circuit voltage is about
1.48V)
600 Vp

12
Replacing the Batteries
6. AC Current : Auto Range
Range
Resolution
Accuracy
Frequency
Response
Overload
protection
2.000 A 1 mA
±(4%+20d
)≦
0.4A
50 Hz -
60 Hz 400 A rms
±(3%+15d
)
20.00 A 10 mA
±(3%+15d
)≦
0.4A
±(2%+10d
)
200.0 A
0.1 A
±(2%+5d)
400 A
1 A
Response: Average responding, calibrated in rms of sine wave
Replacing the Batteries
WARNING
To avoid electric shock, make sure that the test leads have
been clearly move away from the circuit under measurement
before opening the battery cover of the meter.
1) If the sign appears, it means that the batteries should be
replaced.
2) Loosen the fixing screw of the battery cover and remove it.
3) Replace the exhausted batteries with new one.
4) Put the battery cover back and fix it again to its origin from.
Note:
Do not reverse the poles of the batteries.