Aerospace Glossary Letters H - K


H

Harmonized – Products meeting requirements of CENELEC for use in European Economic Community.
Harness – An arrangement of wires and cables, usually with many breakouts, which have been tied together or pulled into a rubber or plastic sheath, used to interconnect electric circuits.
Hash Mark Stripe – A non-continuous helical stripe applied to a conductor for identification.
Heat Distortion – Distortion of a material due to the effects of heat.
Heat Shock – A test to determine stability of a material by sudden exposure to a high temperature for a short period of time.
Helical Stripe – A continuous, colored, spiral stripe applied to a conductor for circuit identification.
Hertz (Hz) – A term replacing cycles-per-second as a unit of frequency.
Hi-Pot – A test designed to determine the highest voltage that can be applied to a conductor without electrically breaking down the insulation.
Hook-Up Wire – A single insulated conductor used for low current, low voltage (usually under 1000 Volts) applications within enclosed electronic equipment.
Hygroscopic – Readily absorbing and retaining moisture.
Hypalon – DuPonts trade name for their chlorosulfonated polyethylene, an ozone-resistant synthetic rubber.

I

Impact Strength – A test for determining the mechanical punishment a cable can withstand without physical or electrical breakdown by impacting with a given weight, dropped a given distance, in a controlled environment. 
Impedance – The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and reactance X, measured in ohms.
Index of Refraction – The ratio of the velocity of light in free space to the velocity of light in a given material.
Inductance – The property of a circuit or circuit element that opposes a change in current flow, thus causing current changes to lag behind voltage changes. It is measured in henrys.
Insulation – A material having high resistance to the flow of electric current.
Insulation Resistance (I.R.) – That resistance offered by an insulation to an impressed dc voltage, tending to produce a leakage current through the insulation.
IEC – International Electrotechnical Commission.
IEEE – Abbreviation for Institute of Electrical and Electronics Engineers.
Interconnecting Cable – The wiring between modules, between units, or the larger portions of a system.
Interference – Electrical or electromagnetic disturbances which introduce undesirable responses into other electronic equipment.
Interstices – Voids or valleys between individual strands in a conductor or between insulated conductors in a multiconductor cable during extreme flexing.
IPCEA – Abbreviation for Insulated Power Cable Engineers Association.
Irradiation – In insulations, the exposure of the material to high energy emissions to alter the molecular structure by crosslinking.
ISA – Instrument Society of America.
ISO – International Standards Organization.

J

Jacket – An outer covering, usually non-metallic, mainly used for protection against the environment.

K


Kilometer (km) – 1000 meters or 3,281 feet (0.621 miles).
KPSI – Tensile strength in thousands of pounds per square inch.
Kynar – Pennwalt trade name for polyvinylidene fluoride, a fluorocarbon material typically used as insulation for wire wrap wire.