MEWOI MEWOI7900 User manual

ROGOWSKI COIL CURRENT CLAMP

USER MANUAL
www.mewoi.com

CONTENT
Warning.....................................................................................................1
I Introduction.............................................................................................3
II Electrical Signs......................................................................................5
III Technical Specifications......................................................................6
IV Structure of the Leaker.......................................................................8
V Operating Method ................................................................................9
1. Start-up, Shutdown.........................................................................9
2.Current,leak current Measurement ................................................10
3. Peak Holding ................................................................................13
VI Function Quick Look Up...................................................................15
VII Display Example and Meaning......................................................15
VIII How to Change Battery..................................................................16
IXAccessories........................................................................................17

-1-
- 2-
Warning
Thank you for purchasing our company's High Accuracy Clamp
Leaker, for better use of this product, please:
——Read carefully the user's manual.
——Follow strictly safety rules and notes listed in this manual.
Under any circumstances, please pay special attention to your safety in
the course of using this instrument.
Give heed to label texts and symbols on panel and back plate of this
instrument.
Please don't place and store this instrument in hot and humid condition,
Locations with moisture condensation and under direct sunlight for a long
time.
In case voltage of battery was low, please replace batteries.
The instrument doesn’t have automatic shutdown function, please
shutdown after use it.
Cannot be used to test voltage higher than 600V lines.
Forbid to use if the rear cover of the instrument and the battery cover plate
are not covered.

-2-
If the shell or the test line breaks down and causes the metal to be
exposed, please stop using it.
The instrument and the flexible clamp must be maintained regularly, keep
clean, and cannot be wiped with corrosion agent and rough material.
Avoid bending of the flexible tongs to avoid breaking the coil.
If you expect not to use the instrument for a long time, please take out the
batteries.
When changing batteries, please pay attention to the polarity of battery.
Use, disassembly and maintenance of this leaker shall be operated by
authorized personnel.
If the continued use will bring danger, it should be immediately stopped
and sealed immediately and handled by an authorized institution.
Users shall carry out operation based on danger signs “ ” on
instrument and manual.
The " " danger sign on the instrument and the manual, must be safe
to operate in accordance with the instructions.

-3-
I Introduction
The MEWOI7900 Rogowski current clamp is designed for the test of big
current and leakage current. It is widely used in the fields of electric power,
communication, meteorology, railway, oil field, construction, measurement,
scientific research and teaching units, industrial and mining enterprises and
so on. The cable is especially suitable for intensive places, the current
industrial environment such as the wall- subway transformer core current test,
thick wire cable test, relay protection, silicon controlled rectifier, inverter,
semiconductor switch, power electronic conversion equipment, arc welding
and other serious distortion of the signal of the test.

-4-
Flexible current clamp, namely Rogowski Coil (Rockwell coil), is a circular
coil uniformly wound on non-ferromagnetic materials, no hysteresis effect,
almost zero phase error, no magnetic saturation, high linearity, strong
anti-interference ability. The output signal is the differential of current to time.
By integrating the output voltage signal, the input current can be truly
restored, and the current range can be from mA to 10000A. Flexible coil
current clamp part without any bare metal conductor, non-contact
measurement, safe and fast; the small size and light weight, beautiful
appearance, soft and flexible, suitable for narrow environment and cable
intensive sites; high accuracy, strong reliability, frequency bandwidth, users
can be customized according to the length of the coil.
The instrument also has the functions of peak retention, data retention, data
storage and so on. It is a necessary tool for electrical safety inspection.

-5-
II Electrical Signs
Extremely dangerous! Operators shall strictly keep to
safety rules; otherwise there would be dangers of electric
shock to cause personal injuries or casualties.
Dangerous！Operators shall strictly keep to safety rules;
otherwise there would be dangers of electric shock to
cause personal injuries or casualties.
Warning！Operators shall strictly keep to safety rules;
otherwise personal injuries or equipment damages might
be caused.
Double insulation
AC
DC

-6-
III Technical Specifications
Function
Big AC current, leakage current measurement
Power
Zn-Mn dry battery,6F22,9V
Test Mode
Flexible CT:the output signal is the differential
of the current to the time. By integrating the
output voltage signal, the input current can be
restored.
Coil Diameter
φ200mm
Range
AC 0.00A ~ 9999A
Resolution
AC 10mA
Accuracy
2% + 3dgt (the tested wire is in the central
position of the flexible coil, 23℃±2℃)
Coil length
628mm
Coil thickness
Coils of thickness (7.5mm) (very suitable for a
narrow environment and a dense line of rows,
etc.)
Frequency
50Hz/60Hz (automatic recognition)
Display Mode
Four digits LCD display
Dimension
Width ×Height×Thickness：
190mm×370mm×40mm
LCD Dimension
35mm×21.5mm；display domain：32mm×15mm

-7-
Backlight
Support
Weight
200g
Electric field
interference
has no hysteresis effect and strong
anti-interference ability
Position Error
The position error of the measured wire should
be at the center of the flexible coil as far as
possible, not close to the opening port, and the
test error at the opening port is about twice or
more.
Sampling Rate
2times/sec
Data Memory
99sets, display "FULL" symbol indicates that
the storage is full
Peak Hold
Push HOLD without release, shows the peak
value symbol
Reading Hold
DH indicating the reading is hold
Voltage Range
AC600V
Out of Range
OL indicating the current is out of range
Battery Voltage
Indicating the battery voltage is lower than
7.2V.Then the battery have to be changed
Rated Current
About 8mA
Temperature
and Humidity
Working: 0℃～40℃,below 80%rh
Storage: -10℃～60℃,below 70%rh

-8-
Insulation
resistance
100M Omega or larger, 1000V
Applicable
Safety Rules
IEC1010-1、IEC1010-2-032、pollution grade 2、
CAT VI (1000V) IEC61326 (EMC standard)
IV Structure of the Leaker
1. Flexible Coil 2. Locking or opening a coil in the direction of the arrow.
3. POWER key 4.LCD
5. HOLD Key 6.Uper Cover
7. Back cover 8.Battery
cover

-9-
V Operating Method
1. Start-up, Shutdown
Short Press POWER key to start up, LCD will begin to display; Press the
POWER key again to shut down. After starting up for 5 minutes, LCD will
flick to remind that the instrument will shut down automatically; after
flickering for 30s, it will shut down formally to reduce battery
consumption. In case you have pressed POWER key when LCD was
flickering, the leaker will continue to work for 5 minutes. If LCD was
very dark after starting up, it might be caused by low-voltage battery, in
this case, please change battery immediately.

-10-
2.Current,leak current Measurement
High voltage, extremely dangerous! Operators shall
strictly observe safety rules; otherwise there would be
risk of electric shock to cause personal injuries or
casualties.
Dangerous！Please don’t use it to measure voltage
higher than 600V; otherwise there would be risk of
electric shock to cause personal injuries or equipment
damages.
1）Power on.

-11-
2）According to the OPEN direction of the instrument structure to unscrew the
lock, grabbed the tested wire, and then rotate in the direction of CLOSE to
lock the flexible coil
3）If the instrument displays the "OL" symbol,
indicates that the measured current is
beyond the upper limit of the instrument. The
measured conductor should be in the center
of the flexible coil as far as possible (near the
A point), not near the opening and closing
area (C area). The test error at the opening
and closing points will be increased by one
time or more. The position error near the B
point will increase by 1%.
4）If measured current is small, the resolution
can be improved by closing the flexible coil
over a number of loops repeatedly on the
measured wire. For example, the measured
current is 10mA, and the flexible coil is
circled 3 times around the tested wire. The test instrument displays 30mA,
and the 50mAis displayed around the 5 circles. In this way, the actual current
is equal to the instrument display value divided by the number of flexible coil
winding. See legend reference

-12-

-13-
Clamp the Live Wire or null separately to test the
single current of the line (Note 1 Wire)
Clamp live wire and null line together is to measure
the single phase leakage current. (Note: 2 Wires)
Clamp earth wire is to measure grounding line
leakage current of electrical equipment.
(Note: single wire)
Clamp the three-phase 3 wires together to measure
three-phase 3 wires’leak current.（Note: 3 wires）
Clamp the three-phase 4 wires together to measure
three-phase 4 wires’leak current.（Note: 4 wires）
Clamp the three-phase 5 wires together to measure
three-phase 3 wires’leak current.（Note: 5 wires）
For safety, when measuring high voltage and large
current, please move the instrument away from the
measured wire after confirming the correct
operation test.
3. Peak Holding
Pressing HOLD key continually (more than 3seconds) during
measurement, after the "PEAK" symbol appears, it enters the peak

-14-
acquisition mode. The symbol “ ”shows that the instrument
automatically captures the current peak value in the time period, and
loosely returns to the test state ("symbol “ ” does not show).
4. Hold, Storage and Access Reading
1）Pressing HOLD key(less than 3seconds) for a short time in the
course of measurement (less than 3 seconds), DH symbol will
display, the instrument will hold current measuring data and
automatically stored in the memory with a unit ID; press HOLD key
again to release the hold state, and the instrument continues its
measuring; in case stored data reached to 99 groups, press HOLD
key again, the “FULL” symbol will display, which means storage
memory is full; press HOLD key to cancel “FULL” flickering and
return to measuring mode.
2）Press HOLD key(more than 3 seconds) to enter data access mode
and display Unit 1 storage data automatically; and then press
HOLD key again to turn the page of stored data; NULL will display
when there is no data in stored in the memory, press POWER key to
exit data access mode.
3）After entering into data access mode, press HOLD key for more than
3 seconds will clean up all stored data; when the instrument
displaying “dEL” symbol, it means that it has finished cleanup
process, and then return to measuring state automatically.

-15-
VI Function Quick Look Up
POWER Key Short Press
Power on/shutdown/exit
HOLD Key Short
Press(less than 3 seconds)
Data Holding/release/storage
HOLD Key Pressing
for more than 3s
Peak Holding
(at measuring mode)
HOLD Key Pressing Press
for 3s
Data Access(at measuring mode)
HOLD Key Pressing Press
for 3s
Clear Data(at access data mode)
VII Display Example and Meaning
1.---Measured leakage current is
0.25mA.
2.---Low battery, please change.
3. --- Measured leakage current is 5mA

-16-
---Data Held
---Stored unit ID is NO.03.
4. ---Access the unit 3 of the stored
Data
VIII How to Change Battery
Warning! It is dangerous to carry out test when the
battery cover plate was not on its position.
Please pay attention to the polarity of battery to
avoid damaging the leaker.
Change the low battery in time
If you expect not to use the meter for a long time,
please get off the battery to storage.
1）“ ” symbol means the battery is low and need to be replaced.
2）Short Press POWER key to shut down the instrument; before opening
the battery cover, please make sure that the instrument is turned
off .and then replace with qualified new battery; special attention
shall be paid to the polarity of battery; at last, cover battery cover

-17-
plate.
IX Accessories
Rogowski Coil Tester
1 pc
Bag
1 pc
Battery（6F22 9V）
1 pc
User Manual
1 copy