Teledyne 4040 Instruction, Operating And Maintenance Manual page 61

concentration. If an active (not defeated) alarm has been set to
HIGH at 20.0 ppb, and the analysis concentration is above that
level, then the 'alarm condition' is occurring.
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 in software. 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 main analysis screen will have one or both of the
following messages: 'AL-1', 'AL-2' followed by the instruction
'ENT/ACK'. Pressing ENTER will release a latched alarm. That is, if
there will not be an alarm condition until the analysis concentration is
again violating the trip point. Furthermore, the alarms will be
suppressed until the analysis value is updated, so even though the screen
may be reporting a value that should cause an alarm, until the analyzer
again enters SAMPLE MODE, no alarm condition will reoccur.
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.
Teledyne Analytical Instruments
Operation
61