93-520-20 Issue 3.3
Page 22 of 60
CirrusPro Engineer’s Manual
Sensitivity Settings
The display shows the default Gain and Alarm Thresholds values.
Pipe 1 is shown, changed by selecting the pull down menu.
If the unit is a non-scanning version then the ‘Pipe’ dialog box will appear grey.
Select the box to change any of the Gain or Threshold values, within limits of two rules:
1. Starting from Pre Alarm no gain setting can be higher than any previous value.
2. With scanning units (200DSC, and Pro X4) the gain difference between pipes cannot be
greater than 3.
Gain is set in the range 1 to 10, 10 being the most sensitive. Thresholds can be set from 20 to 90%.
The Algo-Tec setting uses algorithms built into the unit. These have ‘floating’ thresholds based on
current background levels. This background compensation corrects for small changes in background
levels over time. Alarm Threshold values are not relevant in this mode.
Recommended gain levels for most applications are 5 or 6. This is dependent on the background level
of particles. Therefore, the gain should be set to ensure that the background particle level is between
10% and 15% on the bar chart.
