6
MOM200A/600A
ZP-BB04E
BB0141NE
1 INTrODuCTION
1
I
ntroduction
General
This manual is for the MOM200A, and MOM600A
micro-ohmmeters.
The micro-ohmmeter is designed to measure the
resistances of breaker contacts, bus-bar joints, contact
elements in bus-bars and other high-current links.
When contact resistance rises because of oxidation,
loosened or improperly tightened threaded joints,
temperatures rise abnormally at the points of contact.
This abnormal heating reduces conductivity thereby
accelerating the rise in temperature — and this often
leads to serious trouble.
The micro-ohmmeter can be used to detect such pro-
blems early so that they can be remedied long before
trouble starts. Checking contact resistance at regular
intervals provides a clear indication of the state of
your system.
Function description
Connect the instrument to the object being tested.
After you have adjusted the instrument to provide the
desired current through the test object (100 A for ex-
ample), the actual voltage drop across the test object
will be measured automatically, and all you have to do
is press a button to display the actual resistance.
High current is generated and sent out by the instru-
ment during measurement. A miniature circuit breaker
and a thermal cut-out are provided to make certain
this current doesn’t generate excessive heat inside the
instrument.
The instrument is equipped with a device that guards
against induction. A relay short-circuits the sensing
input when the instrument’s ON/OFF switch is off
and also when the instrument is in the mΩ mode.
To protect against external overvoltages, both the
current output and the sensing input are decoupled to
ground.
MOM200A is used for currents up to 200 A.
MOM600A can provide an output current of up to
600 A, and it can be set to six different measuring
ranges.
Full-wave rectified current is used for measuring.
