Open Path Detector Measurement Units; Abbreviations - Honeywell Searchline Excel Cross-Duct Technical Handbook

MAN0889_Issue 3_03/13
B.2 Open Path Detector Measurement Units
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.
Generally, gas readings of LEL.m (Lower Explosive Limit metres) are used. LEL.m is calculated by multiplying
the size of a gas cloud by its concentration.
An open path alarm set at 1 LEL.m would be triggered by any of the situations shown below:
100% LEL
The Searchline Excel Cross-Duct operates with a very short path length, making it reasonable to assume
that the gas concentration is uniform across the duct. Therefore Searchline Excel Cross-Duct uses the duct
width to convert the measured gas reading from LEL.m to %LEL. It is important that the duct width is entered
correctly during commissioning otherwise the detector could report a significant under or over read of gas
concentration.
B.3 Abbreviations
EMC Electro-Magnetic Compatibility
IAA
Instrument Assisted Alignment
IP Ingress Protection
IR Infrared
IS
Intrinsically Safe
LEL Lower Explosive Limit
NPT National Pipe Thread
RFI
Radio Frequency Interference
UL Underwriters Laboratories
Appendix B - Glossary
1m
50% LEL
2m
10% LEL
10m
Searchline Excel Cross-Duct Technical Handbook
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Calibrator
Type SHC1
ESC
Calibrator
Type SHC1
ESC
Calibrator
Type SHC1
ESC