www.miinet.com
Moore Industries-International, Inc.
- 10 -
User’s Manual
225-748-01L
February 2017
Programmable Current/Voltage Safety Trip Alarm
STA
HLPRG
SEC
TION 1
Figure 1.1.
How Alarms
Work
with the Process Input
HIGH ALARM
TRIP POINT
LOW ALARM
TRIP POINT
DEADBAND
RESET
DEADBAND
RESET
IN ALARM
IN NON-ALARM
TIME
The
Trip Point
is the process input level at which the user wants an alarm relay to change state,
typically going into an alarm condition, or “
tripping
”. In the STA, the user sets the trip point for
each alarm relay.
High/Low Alarms;
High Alarms trip when the process input goes above the trip point. Low
Alarms trip when the process input drops below the trip point. Each of the STA relay outputs can
be set by the user to function independently as either high or low alarms.
Latching and Non-latching Alarms
; once tripped, a latching alarm remains in an alarm state
until the input returns to a non-alarm level AND is manually reset. Non-latching alarms return to
a non-alarm state whenever the process input returns to the Reset Point. The STA relays can be
set by the user to function as either latching or non-latching.
The
Reset Point
is the process input level at which the user wants an alarm relay to change
state, typically going from alarm to non-alarm. The reset point is not necessarily the same as the
trip point, because most applications call for a buffer zone or deadband around the trip point to
allow for minute fluctuations in the process input. In the STA, the reset point is determined by the
deadband
setting. Latching STA alarms will not “clear” unless the reset point has been reached
or passed
AND
the manual reset contacts have been shorted.
The
deadband
is the range in which an alarm remains tripped even after the process input has
returned to or passed the trip point. Deadband is not required. When it is not incorporated into a
non-alarm application, the trip point and reset point are the same. The deadband of the STA is
set by the user.
Alarm Terminology
Before setting up the STA, or incorporating the unit in your application, Moore Industries
suggests that all users take a few moments to become familiar with some of the terms
associated with the use of process instrumentation alarms.
