Brochure/Catalogue

Glossary
Initiator PNP/NPN switched Two wires in a three-wire sensor are responsible for keeping the supply
activated. The third connecting wire is used for transferring commands (NO/NC
contact). Initiators with NPN outputs switch the load in active mode towards the
minus potential. Proximity switches with PNP outputs switch toward the plus
potential.
Insulation voltage For electronics components with electrical isolation, this is the maximum AC test
voltage that can be applied for a specied time interval (5 s / 60 s) without
causing a break-through.
Intrinsic safety “i” Electrical equipment for hazardous areas with the ignition protection type
“Intrinsic safety Ex i” Intrinsic safety is divided into ignition protection types “ia”
or “ib” The ignition protection type “intrinsic safety” is a protective strategy that
requires a complex analysis of electronic devices. So it is not only important
to protect intrinsically safe current from the other unsafe circuits. It is also
important to limit the open-circuit voltage, short-circuit current, power, stored
energy and the surface temperature of components that will be exposed to the
explosive atmosphere.
Intrinsically safe circuits are circuits where a spark or thermal effect (as may
occur under the testing conditions specied by EN 60079-11) is not capable
of igniting an explosive atmosphere (of sub-groups IIA, IIB or IIC) or a dust-
air mixture. The testing conditions cover normal operations and certain error
conditions as specied in the standard.
IP protection classes Equipment is assigned an IP protection class to indicate which environmental
conditions it can be used in.
Isolation amplier (active isolator) An isolation amplier is used to provide electrical isolation for analogue standard
signals. They are designed with 2-way or 3-way isolation. The isolation of
the potentials eliminates interference on the measurement signal that can be
caused by earth loops or common-mode noise. The active isolator makes use of
a separate voltage source for its power supply. It functions without feedback; a
change on the output side load does not inuence the input circuit.
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Leakage current The current on the load side of an optocoupler that ows towards the output
circuit while in a closed state.
Limiting frequency The limiting frequency of an analogue signal isolating converter is that frequency
where the output signal is reduced to 1/(sqr2) of the value of the input signal
(approx. 70.7 % = -3 dB).
Line break monitoring Analogue measuring transducer with wire-break detection capability that
permanently monitors the input signal. In the event of an fault (a wire break),
the output signal jumps up to a dened value over the nominal range so that a
controller wired further down the circuit can evaluate the error.
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Technical appendix/Glossary
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