Page 32 - FL-20A Instruction Manual
Model FL-20A Cable Fault Locator
How to Use the 91785 FL Test Box
Description
The 91785 FL Test Box is used to simulate three types of cable faults
(Open, Metallic Short and High Voltage Short). The FL Test Box is
useful in determining if the FL-20A or FL-8A is operating properly.
Note the metal terminals, two on the left and right sides and three in the
center.
The FL Test Box is used to simulate a cable fault at a point in the cable
90% from one side and 10% from the other. The Test Box is labeled
90% on the left side and 10% on the right. If the Blue Probe is placed
on the 90% side, the result should be roughly 90% from the Blue side
(10% from the Red side). The opposite result would be expected if the
Red Probe were placed on the 90% side.
Type of Cable Faults
Of the three types of faults that can be simulated using the FL Test
Box, the first is an Open, which simulates a break in a conductor of
a cable. The second is a Metallic Short which simulates a conductor
directly connected to another conductor in a cable. The last is a High
Voltage Short, which simulates a conductor with a break in the insulation
close to a ground shield, drain wire, or another conductor with a break in
the insulation. In this instance, high voltage can arc from one conductor
to another conductor or ground.
Testing with the FL Test Box
Select the appropriate test and connect the Red and Blue Probes to the
appropriate terminals as directed. The Green ground probe always con-
nects to the appropriate center terminal. The Probes should be placed
over the terminals so that the terminals protrude on the other side.
Testing for Opens Accuracy
For Opens, connect the Blue and Red Probes to the upper terminals and
the Green Probe to the center terminal as shown. Run the Opens test
on the fault locator. We would expect a result where the fault is 90% (or
within our claimed accuracy) from the blue side (10% from the Red side).
These two results should total approximately 100%.
