Rev. 11/10/00
21
Leakage and Resistance
Leakage Test
The
Leakage
test detects intermittent Resistance Faults that do not appear under
normal
VOM
tests. When pairs with Resistance Faults are vacant, galvanic action
forms an insulating oxide layer over the faults leaving them undetectable to
standard ohmmeters. When placed into service, such pairs develop “noisy static”
in a relatively short time. The
Leakage
test is an ohmmeter that uses 135
VDC
to
“punch through” the galvanic corrosion, thus revealing the fault.
NOTE
:
The Sidekick’s internal, 1 Megohm impedance causes this voltage to
appear as approximately 135 Volts when measured by an instrument with
10 Megohms of impedance
.
Procedure
CAUTION: Always test for, and remove any AC and DC voltage present on
the pair before performing the
Leakage
test.
TIP
:
Perform the
Leakage
test in this sequence to allow the 135 VDC to “punch
through the galvanic corrosion” on the pair.
1.
Turn the
MODE SWITCH
to the
OFF
position
2.
Connect test leads; Black, Red, and Green to; Tip, Ring, and Ground.
3.
Verify that the
REV SWITCH
is toggled to the
UP
position
4.
To test Tip-to-Ring
, turn the
MODE SWITCH
to
LEAKAGE RX10K
. Then
wait approximately 15 seconds. Next, toggle the
REV SWITCH
to the
DOWN
position. Again, wait approximately 15 seconds.
5.
Read the metered Leakage value.
NOTE
:
The Leakage value is determined by multiplying the ohms reading on
the meter’s red scale by 10,000; it should remain steady at or above
3.5 megohms* during every segment of the test sequence.
6.
To test Tip-to-Ground
, toggle and hold the
TIP SWITCH
UP
for
approximately 15 seconds. Then toggle the
REV SWITCH
to the opposite
position and wait approximately 15 seconds.
7.
To test Ring-to-Earth
, toggle and hold the
TIP SWITCH
UP
for
approximately 15 seconds. Then toggle the
REV SWITCH
to the opposite
position and wait approximately 15 seconds.
*Per Bellcore standards, pairs exhibiting readings below 2 megohms are
unacceptable. However, according to general practice, pairs exhibiting leakage
reading between 2 and 3.5 megohms are still acceptable. Refer to specific
company practices for acceptable megohm readings.
