2
1.2 Glossary of Terms
(As used in this manual)
Alternating Current, AC:
Current that reverses direction on a regular basis, commonly in
the U.S.A. 60 per second, in other countries 50 times per second.
Breakdown:
The failure of insulation to effectively prevent the flow of current sometimes
evidenced by arcing. If voltage is gradually raised, breakdown will begin suddenly at a
certain voltage level. Current flow is not directly proportional to voltage. Once breakdown
current has flown, especially for a period of time, the next gradual application of voltage will
often show breakdown beginning at a lower voltage than initially.
Conductive:
Having a volume resistivity of no more than 103 ohm-cm or a surface
resistivity of no more than 105 ohms per square.
Conductor:
A solid or liquid material which has the ability to let current pass through it, and
which has a volume resistivity of no more than 103 ohm-cm.
Current:
The movement of electrons through a conductor. Current is measured in amperes,
milliamperes, microamperes, nanoamperes, or picoamperes. Symbol =
I
Dielectric:
An insulating material that is positioned between two conductive materials in
such a way that a charge or voltage may appear across the two conductive materials.
Direct Current, DC:
Current that flows in one direction only. The source of direct current
is said to be polarized and has one terminal that is always at a higher potential than the other.
Hipot Tester:
Common term for dielectric-withstand test equipment.
Insulation:
Gas, liquid or solid material which has a volume resistivity of at least 1012
ohm-cm and is used for the purpose of resisting current flow between conductors.
Insulation Resistance Tester:
An instrument or a function of an instrument capable of
measuring resistance's in excess of 200 megohms. Usually employs a higher voltage power
supply than used in ohmmeters measuring up to 200 megohms.
Leakage:
AC or DC current flow through insulation and over its surfaces, and AC current
flow through a capacitance. Current flow is directly proportional to voltage. The insulation
and/or capacitance are thought of as a constant impedance, unless breakdown occurs.
Resistance:
That property of a substance that impedes current and results in the dissipation
of power, in the form of heat. The practical unit of resistance is the
ohm.
Symbol =
R
Trip Point:
A minimum or maximum parameter set point that will cause an indication of
unacceptable performance during a run test.
Voltage:
Electrical pressure, the force which causes current through an electrical conductor.
Symbol =
V