Using alarms
The alarms can be set for CO
2
or H
2
O (in the LI-850). Each alarm features an activ-
ation level and a deadband. The high alarm is activated if the measured con-
centration exceeds a high threshold. The high deadband is the range below the
threshold that the alarm remains activated. The low alarm is activated if the meas-
ured concentration drops below a low threshold. The low deadband is the range
above the low threshold that the alarm remains activated.
Elapsed Time
CO
2
Concentration, ppm
300
400
700
600
Low Deadband
High Deadband
500
Low threshold = 300;
Alarm activated when
CO2 <300 ppm
High threshold =700;
Alarm activated when
CO2 >700 ppm
High deadband = 100;
Alarm deactivated
when CO2 <600 ppm
Low deadband = 50;
Alarm deactivated
when CO2 >350 ppm
Figure 3-2. An alarm is triggered when a concentration is outside of a threshold. For
example, the high alarm is activated if the CO
2
concentration exceeds 700 ppm. The alarm
is deactivated when the concentration drops below 600 ppm (high deadband = 100). The
low alarm is activated if the concentration drops below 300 ppm and is deactivated when
the concentration rises above 350 ppm (low deadband = 50).
Figure 3-3. The Alarm Settings window is where you configure alarms. The settings shown
here will give the behavior shown in Figure 3-2 above.
Section 3. Configuring the gas analyzer
3-9Using alarms
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