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- Isolation
Separation of one section of a system from undesired influences of other sections. - Linear load
An electrical load device which, in steady-state operation, presents an essentially constant load impedance to the power source throughout the cycle of applied voltage. - Noise
Electrical noise is unwanted electrical signals that produce undesirable effects in the circuits of the control systems in which they occur (for this recommended practice, ‘control systems’ is intended to include sensitive electronic equipment in total or in part). - Non-linear load
Electrical load that draws current discontinuously or whose impedance varies during the cycle of the input AC voltage waveform. - Non-linear load current
Load current that is discontinuous or is not proportional to the AC voltage. - Notch
A switching (or other) disturbance of the normal power voltage waveform, lasting less than a half-cycle, which is initially of opposite polarity than the waveform and is thus subtractive from the normal waveform in terms of the peak value of the disturbance voltage – this includes complete loss of voltage for up to a half-cycle. - Over-voltage
An rms increase in the AC voltage, at the power frequency, for durations greater than a few seconds – see Swell and surge. - Phase shift
The displacement in time of one periodic waveform relative to other waveform(s). - Power quality
The concept of powering and grounding sensitive electronic equipment in a manner that is suitable to the operation of that equipment. - Recovery time
Time interval needed for the output voltage or current to return to a value within the regulation specification after a step load or line change – also may indicate the time interval required to bring a system back to its operating condition after an interruption or dropout. - Recovery voltage
The voltage that occurs across the terminals of a pole of a circuit interrupting device upon interruption of the current. - Shield
As normally applied to instrumentation cables, a conductive sheath (usually metallic) applied over the insulation of a conductor or conductors, for the purpose of providing means to reduce coupling between the conductors so shielded and other conductors that may be susceptible to, or that may be generating, unwanted electrostatic or electromagnetic fields (noise). - Shielding
Is the use of a conducting barrier between a potentially disturbing noise source and sensitive circuitry – shields are used to protect cables (data and power) and electronic circuits – they may be in the form of metal barriers, enclosures or wrappings around source circuits and receiving circuits. - Slew rate
Rate of change of (AC voltage) frequency. - Surge reference equaliser
A surge-protective device used for connecting equipment to external systems whereby all conductors connected to the protected load are routed, physically and electrically, through a single enclosure with a shared reference point between the input and output ports of each system.