Casella CEL Sensus data logger unit - Manual (Page 31)

8.4 Limits
Each alarm channel can compare its data value to either one or two limit
values depending on the test mode selected. For test modes that require
only a single limit value, the data is compared against the first limit value
allocated to the channel. For two limits, it is compared against both.
Both the data and limit values are held in floating-point format, so
some care should be exercised when using the “eq” test mode as the values
may not be exactly equal (displayed values are usually truncated after a few
decimal places).
8.5 Action
Alarms can be used either in isolation or combined with others for more
complex situations. The action parameter for an alarm defines how it
interacts with the next defined alarm channel. Available action modes are
listed below.
Alarm Action Mode
Mode Result,
none Alarm is acting in isolation,
or Alarm result should be logically “or’d” with
the result of the next defined alarm,
and Alarm result should be logically “and’d”
with the result of the next defined alarm.
Any single alarm, or the last alarm in a logical chain, should have its
action mode set to none. Only those alarms with an action mode “none” will
actually trigger an alarm event.
8.6 On/Off Delays
The resultant alarm condition can be filtered with respect to time by defining
on/off delays for the alarm channel. These delays are expressed in seconds
and can be set to any value between 0 and 65535 (approximately 18 hours).
A value of zero means the change of alarm condition will be
processed immediately it occurs. Any other value means the alarm condition
must remain steady in that state for the specified period of time before the
change of condition is processed. Any change of alarm condition within the
specified time period will cause the delay time to be counted again.
8.7 On/Off Values
Each alarm channel can be allocated a pair of data values that it can pass on
to a data channel whenever the alarm changes state. This allows alarm states
to be logged, displayed, used to control the actions of other alarms and affect
the processing of other data values.
8.8 Output Channel
This defines the data channel into which the on/off values are to be written
when the alarm changes state. This should be the channel number of a
passive type channel, as all other channel types automatically collect their
data values during the scan process. To disable this feature, refer to the
section on alarm flags.
Alarms SENSUS Digital Data Logger -
Users Handbook
Page 31 of 44