SAIC Exploranium – GR-135 System Manual page: 33
The AUTO mode automatically changes the vertical scaling to optimize the “chart recorder” screen
display. For example, if the current chart scale is 500 counts and the radiation level is exceeded by
60% of the current scale, the vertical scale changes to the next highest value (in this case to 1K or
1000 counts). If the number of counts exceeds 65535, the chart record scale will remain at 64K.
If the radiation level decreases, the vertical scale will remain its current level (say 2K) until the
“peak” that caused the scale change disappears from the “chart record” (60 samples of data are
displayed at one time.)
The vertical scale changes back according to the 30% rule - that is, the scale decreases such that the
highest value appearing in the chart record is 30% of the maximum vertical scale. In the above
example, the radiation level may drop to 105 counts, at which time the vertical scale returns to 500.
d) AUDIO METER - determines the mode of operation of the Audio meter system
Options are OFF,
AUTO, 50, 100, 150, 200, 250cps
AUTO : In this mode, the variable radiation level digital data displayed on the screen will also give a
variable tone audio which directly follows the radiation level. Thus a sudden increase in
radiation level will give a corresponding increase in audio pitch. This is a very important
feature of the SEARCH mode as it permits a very sensitive “eyes free” search tool. The data
is sampled at a 20Hz (50mSec) rate with an optimized filter to give a quick audio response as
radiation increases.
If this mode is selected, then when the SEARCH mode is started - the first 3 samples are
averaged and a 2 Standard Deviations Audio Alarm Threshold set above this average value.
This stays as the permanent Audio Threshold until the mode is de-selected and re-started.
This method is suitable for most applications as it automatically averages Background levels
to define a reasonable threshold above background.
50..250 : These selections permit a fixed count rate audio threshold to be selected rather than the
automatic selection as above. Once this threshold is exceeded then the audio gives a
variable tone following the variable radiation level
OFF: This selection switches the audio meter OFF to disable the audio search mode
e) ALARM LEVEL: selections are
OFF, 100, 200,250, 300, 350, 400, 450, 500, 600, 700,
1000, 2000, 5000, 9000cps
This selects a specified ALARM THRESHOLD LEVEL. When this threshold is
exceeded a special audio warning tone is heard and the display shows a pop-
up window – see Fig. 31.
Fig. 31
ALARM
ABOVE
LIMIT
WARNING!!
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