P/N 101023281
Metor 900M
Page
33
Rev. 0.5
Installation and Operating Manual
Rapiscan Systems Proprietary Information
APPENDIX A: 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 procedure 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 ot
her’s operation. The effect of the adjacent WTMD can be
minimized by using different operating frequencies.
Operating frequency
- The frequency of the electromagnetic field generated by a WTMD.
Usually WTMDs have several different operating frequencies. When calibrating a WTMD at
the installation site the operating frequency with lowest interference level is chosen. Several
operating frequencies enable also side-by-side use of multiple WTMD without synchronization
cables.
