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1.3. 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 10
3
ohm-cm or a surface resistivity of no more than
10
5
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 10
3
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.
Hypot®: Registered trademark of Associated Research, Inc., for its dielectric-withstand test equipment.
Insulation: Gas, liquid or solid material which has a volume resistivity of at least 10
12
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 is 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
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