Fluke Biomedical 451B - Manual (Page 20)

451B
Operators Manual
10
Freeze Mode
When configured to select the Freeze mode, the MODE button acts as a toggle
switch. Press the button until FREEZE appears on the display. Operation in the
Freeze mode gives the user a constant reference of the highest exposure rate
obtained from the time the freeze function is initialized. The highest reading
appears as a single bar on the bar graph. The current reading continues to
display on the digital display and the bar graph. If a measurement is obtained
which exceeds the freeze bar reading, the freeze bar moves to the higher
measurement point. The operating range of the Survey Meter remains locked on
the highest range attained during the Freeze mode so that the scale and the
multiplier remain the same.
For example, assume the scale units appear as 10, 20, 30, 40, 50, and the
freeze bar is at 47 mR/h on the bar graph. If the Survey Meter then measures a
radiation field of 120 mR/h, the scale units will change to 100, 200, 300, 400,
500, and the freeze bar appears on the graph at 120 mR/h. If the Survey Meter
measurement goes below 100 mR/h, the units on the scale will not change until
the survey meter is taken out of the Freeze mode. However, the digital display
continues to show the current reading. The Survey Meter operates in the Freeze
mode until the user toggles the MODE button to return to the normal operating
mode.
Note
If a measurement is obtained which causes a range change higher
than the alarm set point range, the alarm will sound and continue to
sound until the Freeze mode is disabled.
Integrate Mode
The Integrate mode is operational 30 seconds after the Survey Meter is turned
on and all of the time after that. However the integrated exposure can only be
displayed when the MODE button has been configured as a toggle to display
exposure rate/integrated exposure. If the MODE button is pressed within the
30 second initialization period of the Survey Meter, the display will read “0.”
When integration starts, “0 µR (0 µSv)” displays. Toggle MODE to read exposure
rate as required.
To reset the integration display, toggle the display from the Rate mode to the
Integrate mode. Keep the MODE button pressed for about 5 seconds. The
display will clear, and then read “0 µR (0 µSv).” Exposures are accumulated up
to 999 R (9.99 Sv).