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5.2. Temperature protection
The time of MPK-204 continuous use is limited by thermal considerations.
Some internal sensors measure the temperature of the sensitive parts
and trigger the protection that will cut the current circulation, if any of them
exceeds the limit temperature, thus avoiding any damage. The
overheating Led
appear in the display. Under these conditions, measurements will be
inhibited in the 10 A and 200 A ranges. Measurements in other scales
may be carried out normally, though the LED indicator keeps on being
displayed up to the temperature decreases sufficiently.
5.3. Inductive resistances
The measurement of highly inductive resistances (coil resistances in big
transformers and engines) should be carried out with test current up to
1 A. The 10 A range can also be used, but the time to achieve the
stabilization will be longer. It is not advisable to use the 200 A range in
order to measure the resistances of coils belonging to transformers and
engines. Inductance limits the growth speed of the test current. It is very
useful to employ the test current analogue indicator to see the growth of
this current, and determine when it is stabilized. While the current is
growing its variation generates an e.m.f. on the inductance that causes an
overrange reading. Therefore, it is necessary to wait the current to be
constant to be able to measure the actual resistance.
In order to reduce the time it is convenient to take the Test current
control
control up to its maximum position (fully clockwise) and
observe the current increase in the indicator. When it is near the 100%,
the operator will rotate that control to an intermediate position. Using this
procedure, the skilled operator can stabilize the current in a few minutes
obtaining an exact reading of the coil resistances.
will light on and the OVERHEATING message will
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