8.3 Limitations of Resistance Testing
This Test system is capable of sourcing 10 A at 0.9 VDC. The cable leads that carry the test current
should have a total resistance not exceeding 40 m
. Beyond the 40 m
the test set decreases the
available output current. A warning message,”Use 1 A range” will be displayed. However, the
system will continue to measure and display slightly less accurate results. If the message, ”Rx Too
High” or ”+++.+” is viewed in the display, then mandatory range switching must be complied with.
8.4 Transformer windings
Use of any micro ohm meter for high inductive winding resistance is not recommended.
The inductive characteristics of transformer winding testing require a long period to saturate the
winding to get a stable reading. In addition, care must be taken when removing test leads such that
a voltage charge does not remain on the winding. Lethal currents may remain and might cause
personal injury and damage to the instrument. Specialized test sets with higher potential
compliance voltages and current should be considered for winding resistance measurements.
8.5 Low Resistance Testing
The Micro Junior 2 is an extremely useful device for checking Switch Contacts, SF6 Switchgear,
Busbars, Splices, Joints, Fuses, Breaker contacts, Railbonds, and Low inductive windings.
The Micro Junior 2 utilizes a 4 wire measuring technique. The Two connections on the front plate
marked
+I
& -I are the current leads. The Two connections on the front plate marked
+P
& -P are
the Potential sense or Voltage measuring leads.
By connecting a test specimen to the Current leads and applying the Potential leads across the
resistance to be measured. The points where the potential leads are connected determine the
resistance reading.
The test set employs a very simple principle of Ohm’s law:
R
=
V
I
R
= Resistance,
V
= Voltage,
I
= Current
90081-2.11 Micro Junior 2
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