Glossary I
IC: Integrated Circuit - also known as a "chip".

Impedance:Similar to resistance but applies to AC circuits. The opposition a component in a circuit offers to the flow of alternating current at a given frequency. If the frequency changes, the impedance changes too. Impedance is measured in ohms and has the symbol "Z" with unit ohm.

Inductance: A changing current in a coil produces a changing magnetic flux. The changing magnetic flux results in an induced current flowing in the coil. The unit is a Henry. One Henry is the inductance of a circuit that produces a counter-force of 1 volt when the current flowing is changing at the rate of 1 amp per second.

Infrared: An area in the electromagnetic spectrum extending beyond red light from 760 nanometers to 1000 microns (106 nm). It is the form of radiation used for making non-contact temperature measurements.

Input: That part of a circuit that accepts a signal for processing.

Input Impedance: The resistance of an instrument as seen from the source. In the case of a voltmeter, this resistance has to be taken into account when the source impedance is high; in the case of an ammeter, when the source impedance is low.

Insulator: Any material that resists the flow of current.

Integrated Circuit: Commonly called an IC. A circuit component consisting of a piece of semiconductor material containing up to thousands of transistors and diodes.

Interference: A disturbance to the signal in any communications system.

Interface: The means by which two systems or devices are connected and interact with each other.

Interpreter: A system program that converts and executes each instruction of a high-level language program into machine code as it runs, before going onto the next instruction.

Interrupt: To stop a process in such a way that it can be resumed.

Intrinsically Safe: An instrument which will not produce any spark or thermal effects under normal or abnormal conditions that will ignite a specified gas mixture.

Inverter: A circuit in both analogue and digital systems that provides an output that is inverse to the input. Also a circuit that converts DC to AC.

Isolation: The reduction of the capacity of a system to respond to an external force by use of resilient isolating materials.

Isopotential Point: A potential which is not affected by temperature changes.

Isothermal: A process or area that is a constant temperature.