Major tech MT790 User manual

INSTRUCTION MANUAL
1000A AC POWER
CLAMP METER
MT790

2

3
Contents Page no
1. Overview..........................................................................................4
2. Unpacking Inspection........................................................................4
3. Safety Information............................................................................5
4. Rules for Safe Operation.....................................................................5
5. The Meter Structure...........................................................................6
5.1. The Meter Back and Bottom Structure..........................................6
5.2. The Meter Front Structure..........................................................7
6. Function...........................................................................................8
7. Display Symbols................................................................................9
8. Measurement Operation...................................................................10
8.1. Preparation............................................................................10
8.2. AC Voltage (Main Display) + Frequency (Secondary Display).........11
8.3. AC Current (Main Display) + AC Voltage (Secondary Display)........12
8.4. Active Power (Main Display) + Phase Angle (Secondary Display) .......
Measurement..........................................................................13
8.5. Reactive Power (Main Display) + Reactive Power (Secondary...........
Display) Measurement.............................................................18
8.6. Apparent Power (Main Display) + Phase Angle (Secondary Display)..
Measurement..........................................................................18
8.7. Power Factor (Main Display) + Phase Angle (Secondary Display)
Measurement..........................................................................18
8.8. Active Energy (Main Display) + Time (Secondary Display)
Measurement..........................................................................20
9. True RMS and Average Value Measurement.........................................21
10. Specifications..................................................................................22
10.1. Accuracy..............................................................................22
10.2. AC Voltage (True RMS)...........................................................22
10.3. Frequency............................................................................22
10.4. AC Current (True RMS)...........................................................22
10.5. Active Power ( W=V x A x COSθ)...........................................22
10.6. Apparent Power (VA = V x A)..................................................23
10.7. Reactive Power (Var = V x A x SINθ)......................................23
10.8. Power Factor (PF = W / VA)....................................................23
10.9. Phase Angle (PG=acos (PF))..................................................23
10.10. Active Energy (kWh)..............................................................24

4
1. OVERVIEW
This Operating Manual covers information on safety and cautions. Please
read the relevant information carefully and observe all the Warnings and
Notes strictly.
This clamp is a three phase intelligent handheld digital power clamp meter
(hereafter referred to as "the Meter") which has both the features of
digital current meter and also power measurement meter.
The Meter can measure Voltage, Current, Active Power, Apparent Power,
Reactive Power, Power Factor, Phase Angle, Frequency, Active Energy and
etc.
2. UNPACKING INSPECTION
Open the package case and take out the Meter. Check the following items
carefully to see if there are any missing or damaged parts:
WARNING: To avoid electric shock or personal injury, read the
"Safety Information" and "Rules for Safe Operation" carefully
before using the Meter.
1 English Operating Manual 1 piece
2 Red Test Lead 3 piece
3 Red/Blue Test Lead 1 piece
4 Red/Yellow Test Lead 1 piece
5 Black Test Lead 1 piece
6 Red Alligator Clip 1 piece
7 Red Alligator Clip 1 piece
8 Yellow Alligator Clip 1 piece
9 Black Alligator Clip 1 piece
10 USB Interface Cable 1 piece
11 Software 1 piece
12 Carry Case 1 piece
13 9V Battery 1 piece
Item Description Qty
In the event you find any missing or damaged, please contact your dealer
immediately.

5
3. SAFETY INFORMATION
This Meter complies with the standards IEC61010: in pollution degree 2,
overvoltage category (CAT. III 600V, CAT IV 300V) and double insulation.
CAT. III: Distribution level, fixed installation, with smaller transient
overvoltages than CAT. IV CAT.IV: Primary supply level, overhead lines,
cable systems etc.
Use the Meter only as specified in this operating manual, otherwise the
protection provided by the Meter may be impaired.
In this manual, a Warning identifies conditions and actions that pose
hazards to the user, or may damage the Meter or the equipment under
test.
A Note identifies the information that user should pay attention to.
4. RULES FOR SAFE OPERATION
• Before using the Meter inspect the case. Do not use the Meter if it is
damaged or the case (or part of the case) is removed. Look for cracks
or missing plastic. Pay attention to the insulation around the
connectors.
• Inspect the test leads for damaged insulation or exposed metal.
Replace damaged test leads with identical model number or electrical
specifications before using the Meter.
• Do not apply more that the rated voltage, as marked on the Meter.
• When measurement has been completed, disconnect the connection
between the test leads and the circuit under test, remove the test leads
from the input terminals of the Meter and turn the Meter power off.
• Do not carry out the measurement when the Meter's back case and / or
battery door is opened to avoid electric shock.
• When the Meter working at an effective voltage over 30V in AC, special
care should be taken.
• Use the proper terminals and function for your measurements.
• Do not use or store the Meter in an environment of high temperature,
humidity, explosive, inflammable and strong magnetic field. The
performance of the Meter may deteriorate after dampened.
• Do not use the Meter if the surface of it is wet or the user's hands are
wet.
• When using the test leads, keep your fingers behind the finger guards.
• Replace the battery as soon as the battery indicator appears. With
a low battery, the Meter might produce false readings that can lead to
electric shock and personal injury.
WARNING: To avoid possible electric shock or personal injury, and to
avoid possible damage to the Meter or to the equipment under test,
adhere to the following rules:

6
• When opening the battery door, make sure the Meter is off.
• When servicing the Meter, use only the same model number or identical
electrical specifications replacement parts.
• The internal circuit of the Meter shall not be altered at will to avoid
damage of the Meter and any accident.
• Soft cloth and mild detergent should be used to clean the surface of the
Meter when servicing. No abrasive and solvent should be used to clean
the surface of the Meter.
• The Meter is suitable for indoor use.
• Turn the Meter off when it is not in use and take out the battery when
not using for a long time.
• Constantly check the battery as it may leak when it has not been used
for some time, replace the battery as soon as leaking appears. A
leaking battery will damage the Meter.
5. THE METER STRUCTURE
5.1. The Meter Back and Bottom Structure (see figure 1)
Figure 1
1 - Infrared slot
2 - USB Interface Cable

7
1 - 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.
2 - Hand Guards: to protect user's
hand from touching the
dangerous area.
3 - MR button (recall data)
4 - SEL / ▲ button (press to select
phase and sum of Watts
measurement)
5 - MAXMIN / ▼ button
6 - SAVE button (data store button)
5.2. The Meter Front Structure (see figure 2)
7 - LCD Display
8 - L2 Input Terminal
(Second phase measurement)
9 - L3 Input Terminal
(Third phase measurement)
10 - COM Input Terminal
11 - L1 Input Terminal
(First phase measurement)
12 - USB button
13 - CLEAR button
14 - LIGHT button (auto display
backlight button)
15 - Σ button (Sum)
16 - HOLD button
17 - Rotary function switch
18 - NCV indicate lamp
Figure 2

8
Press HOLD to enter the Hold mode in any mode, appears
and the Meter beeps.
Press HOLD again to exit the Hold mode to return to
measurement mode, the Meter beeps and, disappears.
Press the backlight button when needed. The backlight will
auto off after 20 seconds. Press the button again to turn the
backlight off manually.
At Active power (main display) + Phase angle (secondary
display) mode, press Σ once button to sum up the current
phase of 3 phase measurement results. Then carry out second
phase power measurement.
Press Σ and hold for over 1 second to sum up the phase
power measurement result which had been selected.
If you didn`t select any phase of 3 phase, Σ is invaild.
Press once to store single reading, and the Meter beeps. The
index number shown on the left secondary display will keep
on increasing. The maximum number of data store is 99,
when it has achieved 99, the Meter shows .
Press SEL button to step through first phase, second phase,
third phase and the sum of watts.
Press SEL and hold for over 2 second to enter 3P3W mode.
Press to start recording maximum & minimum, this is only
valid in voltage, current, active power and apparent power
ranges only.
At active energy range, press CLEAR and hold for over 1
second to reset time to zero, then restart the timing.
At all other ranges, press CLEAR and hold for over 1 second
to clear stored readings.
Press once to enter Memory Record mode, appears and
the Meter beeps.
If the Meter steps through the sum of power press ▼/▲
button to switch display of active power (main display) , sum
of reactive power (secondary display) , sum of power factor
(main display) and sum of apparent power.
In the MR mode, press ▼/▲ to select recoded data.
Measurement data will be sent to the PC
Button Operation Performed
6. FUNCTION
Below table indicated for information about the functional button
operations.
HOLD
Σ
SAVE
SEL
MAXMIN
CLEAR
MR
▼/▲
USB
H
H
FUL
MR

9
1. Turn the rotary switch dial to a position away from the OFF position.
Hearing a beep sound indicates the meter is turned on. The LCD
displays all symbols firstly and then return to the normal mode. If the
symbol is displayed, please changed the battery.
2. After auto-shut-off, there are some parts of the circuit of the meter
which still work. If no measurement is needed in a longer time, you'd
better turn the rotary switch back to the OFF position.
3. Press the backlight button when needed. Auto shut-down backlight
after 20 secs. Press the button again, turn the backlight off manually
7. DISPLAY SYMBOLS (See figure 3)
Figure 3

10
Data Output is in progress
First phase symbol
Second phase symbol
Third phase symbol
Unit for hour mm
Unit for minute
Hz: Hertz.The unit of frequency.
PG: The unit of phase angle
KVAr. The unit of reactive power
Watt: Sum of Watt
The battery is low. Warning: To avoid false readings,
which could lead to possible electric shock or personal
injury, replace the battery as soon as the battery
indicator appears.
Unit for second
Maximum and Minimum reading
Analogue Bar Graph
Overloading
Bar graph
Indicator for clear the stored reading
Negative symbol
High voltage symbol
Indicator for AC voltage or current
Indicator for recall the stored reading
Frequency symbol
Indicator for data store
Indicator for data stored is full
Data hold is active
Button Operation Performed
h
HZ
PG
KVAr
Σ W
S
CLEAR
AC
MR
Hz
MEM
FUL
USB
mm
MAX/MIN
8. MEASUREMENT OPERATION
8.1. Preparation
• Dial the Rotary to any active measure range
• Replace the battery as soon as the battery indicator appears on the
display.
• Non-Contact Voltage Detector
WARNING: Risk of Electrocution. Before use, always test the Voltage
Detector on a known live circuit to verify proper operation.
H
0
20 40 60 80
100
Ø1Ø1
Ø2Ø2
Ø3Ø3