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Insulation Resistance ( I.R.) - That resistance offered by and insulation to an impressed DC voltage, tending to produce a leakage current through the insulation.

Insulation Thickness - The wall thickness of the applied insulation.

Interconnecting Cable - the wiring between modules, between units, or the larger portions of a system.

Interference - and undesired electrical signal induced into a conductor by electrical or electromagnetic means.

Interstices - voids or valleys between individual strands in a conductor by electrical or electromagnetic means.

Ionization - The formation of ions. Ions are produced when polar compounds are dissolved in a solvent and when a liquid, gas, or solid is caused to lose or gain electrons due to the passage of an electric current.

ISA - Instrument Society of America

ISO - International Standards Organization