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MAN0530 Issue 10 - 11/09
Searchline Excel
2104M0506
APPENDIX B - GLOSSARY
B.1 TERMINOLOGY
Ex d
Flame proof or explosion proof within the confines of European standards EN60079-0 and
EN60079-1. An enclosure that can withstand the pressure developed during the internal
explosion of an explosive mixture and that prevents transmission of the explosion to the
explosive atmosphere surrounding the enclosure.
Ex e
Increased safety within the confines of European standards EN60079-0 and EN60079-7
applied to electrical apparatus that does not produce arcs or sparks in normal service, in
which additional measures are applied so as to give increased security against the possibility
of excessive temperatures.
Instrument Assisted Alignment (IAA)
A method of commissioning the Excel system using the associated electronic Handheld
Interrogator device. The process will not allow the Excel system to initialise unless the
alignment of the Receiver and Transmitter is correct and the signal strength is correct.
IS
Intrinsically safe, apparatus in which the circuits themselves are incapable of causing ignition
of a flammable gas.
Lower Explosive Limit (LEL)
The volume of flammable gas or vapour in air below which an explosive gas atmosphere will
not be formed.
RS485
An industry-wide serial communication link protocol.
Turbo heating
Increased Transmitter window heating at low operating temperatures.
B.2 MEASUREMENT UNITS
LEL.m
Lower Explosive Limit metres. Open path detectors measure the amount of gas present in
the beam. However, they cannot discriminate between a low concentration gas cloud over
a large area and a high concentration gas cloud in a small area. % LEL has little meaning in
this situation and so gas readings of LEL.m are used. LEL.m is calculated by multiplying the
size of a gas cloud by its concentration.
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