General Description
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Major Megger MJ159, MJ160, MJ359, MJ459, and
MJ559 testers are compact instruments designed to give
rapid, accurate and direct measurement of continuity and
insulation resistance of domestic and industrial wiring, cables,
transformers, motors, generators electrical machinery and
appliances.
Being self-powered, the instruments are suitable for use
during installation and commissioning work as well as for
service and maintenance applications.
Insulation measuring range is 0,1 Ω to 2000 MΩ (MJ160
0,1 Ω to 1000 MΩ). Automatic discharge for capacitive circuits
under test is provided.
A guard terminal can be used to minimise the effects of
surface leakage when carrying out insulation resistance tests.
In addition each instrument has a 5000Ω Resistance range
making them ideal for testing electrical installations.
Nominal test voltages are 100 V, 250 V, 500 V and 1000 volts
selectable. (MJ160: 50 V, 100 V, 250 V and 500 volts).
All instruments have a mains (line) voltage measuring range
of 0 to 600 V. Although calibrated for a.c voltage, this feature
will give decaying voltage indication following the testing of
equipment possessing capacitance.
The instruments use a moving coil meter with taut band
suspension; white scales on a black scale plate and an
orange ‘dayglow’ needle indicates the resistance value being
measured.
MJ159 and MJ160 are powered by a low voltage, hand
cranked, brushless a.c generator which is connected, after
rectification, to a d.c. to d.c. converter. The generator is
designed to be easy to turn even under full load.
Dual powered units are mains (line) powered with either an
internal hand cranked generator, or battery cells that are re-
chargeable by the instrument’s internal charger.
The MJ359 is dual mains (line) or
hand cranked generator
powered.
The MJ559 is dual mains (line) or
rechargeable battery
powered.
Power for the MJ459 is derived from six 1,5 V (IEC LR6)
cells. The cells are connected to a d.c. to d.c. converter to
provide the test voltages.
MJ459 and MJ559 are fitted with a button switch to enable
the battery charge to be checked.
The case is robust, yet light-weight, made from a strong
polycarbonate plastic. Mounted on top of the case is a 5
position, rotary, range selection switch and a ‘Test push
button.
Three shrouded 4 mm terminal sockets marked ‘-’, ’G’ and ’+’
are provided on the side of the case for test lead connection.
Test lead resistance is included in the instrument calibration.
For this reason, only the test leads supplied or replacement
ones should be used.
After the test leads have been connected to the instrument
terminals, the carrying handle folds down neatly over them.
Should the carrying handle accidentally become detached
from the case it may easily be ‘sprung’ back into position.
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