Chapter 5 Parameters Definition
108
During Occupied Sensor Hold Time While Positioning: The occupant is
assumed to be present in the monitor this is to give the occupant time to position
or turn around (where applicable) without triggering the “Monitoring not
complete, please re-monitor!” warning. For the default values are: 0.5 s for the
“One-Step” ode, 0 s for the “Walk-Through” mode and 3.0 s for the “Two-Step”
mode.
If occupied sensor is present (see F2 – Operation Configuration) then both the
Occupied Sensor Hold Time and While Positioning settings extend the time
the occupied sensor is active. These are both forced to zero if both Hot & Cold
side barriers are installed (see F4 – Access Configuration on page 28) and
Extend Occupied Time (see below) is used. If the monitor is deemed occupied
with both barriers closed, then the monitor is assumed occupied until, one barrier
opens regardless of position and occupied sensors.
Monitor Time Minimum/Maximum: These items limit the allowable range for
monitoring time. They override the calculated monitoring time based on the release
limit and background count rate if the calculated time is too short or too long. These
limits apply to both positions in 2-step mode.
If the calculated monitoring time exceeds the Maximum then the unit can either be
taken Out of Service automatically (High Count Time) or continue to monitor with
reduced accuracy using the specified maximum monitor time, as discussed in High
Background Rate Settings and Strategy on page 279. The default is 30 seconds.
Note: To achieve the pre-set alarm confidence and false alarm rates the software
automatically calculates and adjusts required count time – rounded up to the
nearest whole number (based on the settings of the two and of the Alarm
Activity, and on the measured background and detection efficiency). If the
count time is limited (by the Monitor Time Maximum setting) to a value
lower than actually required, the statistics of a measurement is not met (the
sample size is too small to satisfy statistical requirements) and consequently
reliability of the alarm is not as good as expected (as per Background Rate
Reset on page 278 and Alarm Settings and Strategy on page 285).
To examine this, please see the graphs in the F5 – Information Menu
specifically, F4 – Monitor Time vs. Bkg Rate on page 246, F5 – Monitor Time
vs. Alarm Value on page 247 and F6 – Monitor Zone Status on page 250.
The increments are by 0.125 s while in the “Walk-Through” mode and by 1 s
otherwise.
Contaminated Message Latch Time: This sets the time that the “Contaminated”
message remains on the display after all the positioning sensors are deactivated. The
default is 2 s. The logic shown in the Logic Flow Diagram on page 51 uses this value.
Clean Message Latch Time: This sets the time that the “Clean” message remains on
the display after all the positioning sensors are deactivated. The default is 1 s. The
logic shown in the Logic Flow Diagram on page 51 uses this value.
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