Teledyne GC-Pro/TCD - Gas Chromatograph - Manual (Page 85)

GC-Pro TCD Operation
Teledyne Analytical Instruments 71
The user can also select the group to which the Alarm will be
associated by using the UP/DOWN arrows adjacent to the Source box.
The configurable items are as follows:
DEFEATED: If an alarm is defeated, its relay is de-energized,
regardless of failsafe condition. A defeated alarm does not react to a
transition over its trip point in either direction.
HIGH: If an alarm is set as HIGH, it will not create a new alarm
condition (see latching) if the analysis concentration is below the trip
point, if the analysis concentration is above the trip point, then an alarm
condition will be created or maintained.
FAILSAFE: A non-defeated alarm that is in FAILSAFE mode
energizes an alarm relay in a non-alarm condition and de-energizes an
alarm relay in an alarm condition.
Note: Failsafe condition of an alarm is a software property. This
is not related to relays that have both normally-open and
normally-closed terminals.
LATCHING: The latching property configures the alarm such that the
user must manually relieve the alarm condition even though the
concentration no longer violates the trip point of the alarm. So, if an
alarm is NON-LATCHING, and the analysis concentration temporarily
drifts above the trip point of a HIGH alarm, the alarm condition occurs
only during the time the concentration is above the trip point. If that
alarm were LATCHING, the alarm condition would persist (even though
the concentration is no longer above the trip point), until the user
released it.
RELEASING A LATCHED ALARM: When alarm conditions are
present, the relay associated with that alarm changes state. To reset from
an alarm condition, enter the Alarm 1 or Alarm 2 screen and disable the
alarm. Then re-enable the alarm. If the alarm condition still exists, the
alarm will again trigger.
TRIGGER POINT: This is the threshold at which an active alarm can
enter into alarm condition. If an alarm is HIGH, ACTIVE, and set at
20.00 ppb, then when the analysis concentration is at or above 20.00 ppb
an alarm condition is initiated or maintained.