PAGE 4 Metor 6M
Installation and Operating Manual
1. PREFACE 92102916 REV 5
Definition of terms
Some special terms used in this manual are explained below.
WTMD - Walk Through Metal Detector
Sensitivity - Parameter for defining the size of the metal items that will generate an
alarm. When sensitivity is increased smaller metal items will be detected.
Discrimination - The WTMD’s ability to differentiate harmless items from
weapons. The alarm rate of a WTMD at a security check point indicates the
discrimination ability of the equipment. Discrimination is affected by several
factors e.g. sensitivity level, passenger profile, season (cold or warm) etc.
Unwanted alarm - (=nuisance alarm). Alarm caused by harmless metal items that
people carry with them through the WTMD.
False alarm - Alarm caused by some other reason than metal objects (e.g.
electrical interferences). Alarms caused by metal objects (wanted or unwanted) are
not false in the case of a metal detector.
Alarm rate - The amount of alarms due to metal items as a percentage of the total
number of people passing through the WTMD. The alarm rate is affected by the
discrimination ability of the WTMD. If discrimination is poor i.e. there are a lot of
alarms due to harmless items the alarm rate is higher. Note! Alarms caused by
electrical interferences or reasons other than items taken through the WTMD,
are not included in the alarm rate.
Throughput rate - The maximum number of people in a given time that can pass
through without affecting the detection performance of the WTMD. Represents the
WTMD’s ability to return to stand-by condition after a person has walked through.
In practice, the maximum throughput rate is only theoretical and can usually not be
reached because it is limited by the checking prosedure and maximum walking
speed of people.
Object speed response - The ability of a WTMD to maintain the sensitivity level
unchanged when people pass through at different speeds.
Calibration - Procedure to set the parameter values of the WTMD for reaching the
optimal performance according to the requirements of the application.
Side-by-side use - Two or more WTMDs are operated so closely-spaced that their
electromagnetic fields affect each other’s operation. The effect of the adjacent
WTMD can be minimized by using different operating frequencies.
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