FL-20A Instruction Manual - Page 7
Model FL-20A Cable Fault Locator
Definitions
Shorts
Metallic short
A condition where there is direct metal-to-metal contact between two
conductors.
High voltage short
Two conductors without insulation, or a conductor and a shield with no
insulation between them, where there is no direct contact. The condi-
tion is detected only at high voltage when arcing occurs between conduc-
tors.
Intermittent arc
An intermittent arc is a high voltage short present that breaks down mar-
ginally at the selected hi-pot voltage.
Opens
An open is a condition where a single conductor has no continuity from
one end to the other.
Hi-Pot Test
Also called a dielectric withstand test. The purpose of this test is to
charge one conductor to determine if high voltage at a predetermined
level will discharge to ground through the insulation. If too much cur-
rent flows, the conductor is not well insulated and it fails the test.
Loop Resistance
Conductor resistance to the flow of electrical current, measured in
ohms/1,000 feet. Resistance is inversely proportional to the cross-sec-
tional area of the conductor, so when the diameter of the conductor is
doubled, the resistance declines 50 percent. FL-20A tests for metallic
shorts are accurate on conductors with loop resistances of 50 milliohms
or greater. Tests for high voltage shorts are effective on conductors with
resistances of 200-250 milliohms or greater.
Accuracy
The accuracy of the test performed. Ratings are influenced by cable
characteristics such as low loop resistance. Accuracy is reported as fol-
lows:
