Moore Industries STA - Page 66

www.miinet.com Moore Industries-International, Inc.
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User’s Manual
225-748-00P
August 2024
Programmable RTD, T/C, Ohms, mV and Potentiometer Safety Trip Alarm
STA
TPRG
SECTION 7
Broken Wire Detection
The STA is provided with the facility to detect both open circuit and short circuit input. This
broken wire detection must always be enabled. This is essential to ensure that dangerous failure
of the sensor or signal input is detected by the STA and consequently alarmed.
Warning: For HIGH LEVEL INPUT, the Lower Range Value (LRV) must be set higher than zero. Broken
Wire Detection will be disabled if LRV is set to zero and will invalidate the safety function.
Sensor Trimming Enable/Disable
Sensor trimming should be used with extreme care as this facility is allowed to trim the sensor
accuracy by as much as 2% of the trimming point value. It is the user’s responsibility to ensure
that the safety application can tolerate this.
Latching Mode Enable/Disable
The STA is provided with the capability to latch on a trip, i.e. once the output process alarm
relays have de-energized they will remain de-energized until either the manual reset contact is
closed or the unit is power cycled. The use of this facility will be determined by the application.
It is recommended that if the output state is latched externally to the STA, the STA latching option
is disabled. Please note that the fault alarm can be congured to Latch or not Latch on Input
Faults. The Input Fault is latched by default.
Note: For STA units with firmware versions 1.5 and earlier, the fault alarm has no configuration
options, is always latched and cannot be reset by MR.
Remote Manual Reset – Procedural Issues
The STA has a facility for the connection of a remote switch to release the latch on the outputs, if
congured, this includes input faults (congurable in units with rmware V1.5 or later).
This function is meaningful only when automatic latching of outputs and/or input faults is selected
in the conguration. If the manual reset is made part of the safety procedure, it must only be
used under strict supervisory and procedural control. The use of a key operated momentary
contact is suggested.
Process Safety Time
Process safety time is the minimum time from the initiation of a hazardous event to the point
where the hazardous event is unavoidable. Any safety function designed to either prevent the
event or at least mitigate its e󰀨ect must be capable of performing its specied safety function in a
time period very much less than the process safety time.
The STA has a characteristic response time (end to end) of 256mSec. The total diagnostic test
time of the unit is 15 minutes.