ATC770 Microprocessor-Based Pressure/Process Controller 39
options for failsafe mode are either
FS
for failsafe mode, or
nFS
for non-failsafe mode. Press the ▼ or
▲ keys until the upper display changes to the desired value. Press the FUNC key to lock in the
value and advance to the next parameter. Similarly, you may configure Alarm 2
(A2.FSM)
and Alarm
3
(A3.FSM)
.
Carefully consider the Alarm wiring: For failsafe operation the alarm contacts must be wired
differently to have operation as expected. The ATC770 energizes the contact relay during failsafe
operation. This means the NO contact will be held CLOSED during normal operation. In the event
of an alarm or the loss of power to the ATC770, the relay will be de-energized and will then open.
The same holds true for a NC contact. It will be held OPEN during normal operation. In the event of
an alarm condition or the loss of power to the ATC770, the relay will be de-energized and will then
close. In non-failsafe operation the reverse is true, in that a NO acts as a NO and a NC acts as an
NC.
6.2.7 SETTING THE ALARMS VALUE
The Alarm 1Threshold Values, is the value beyond which the Alarm will activate (i.e. the threshold).
Alarm 1 is set in the same engineering units that the Full Scale Value uses. To change or view this
value when in the operating screen, press the FUNC key, when in the main screen, and the lower
display will change to
AL1
with the threshold value in the upper display. Press the ▼ or ▲ keys until
the upper display changes to the desired value. Press the FUNC key to lock in the value and
advance to the next parameter, or press A/M to return to the operating screen. Similarly, you may
configure Alarm 2
(AL2)
and Alarm 3
(AL3)
.
6.2.8 SETTING THE ALARMS MASK RESET TYPE
The Alarm 1 Mask Reset may only be used on alarms configured as inhibited low alarms on startup.
It prevents the alarm from activating (masks the alarm) until the value of the primary input exceeds
the alarm value. To change or view this value when in the operating screen, press the FUNC key
until the lower display changes to
AL.MSK
with
OFF
in the upper display. Press the ▼ or ▲ keys
until the upper display changes to
rESEt
. Press the FUNC key to lock in the value and advance to
the next parameter, or press A/M to return to the operating screen. You may similarly configure
Alarm 2 or 3.
6.3 RETRANSMISSION OUTPUT SETUP
This ATC770 has a retransmission output which can send a signal to a recorder or some other device
that can accept a voltage or current signal.
6.3.1 SELECTION THE RETRANSMISSION OUTPUT
The Retransmission Output Type sets the output to specific voltages or currents. The available
outputs are 0-20 mA, 4-20 mA, 0-10 VDC, -10 to +10 VDC, and 0-5 VDC. To change or view this
value, press the FUNC key until
nonE
and
GROUP
show on the display. Press the ▲ key until
5
shows in the upper display. Press the FUNC key until the lower display changes to
RO.TYP
, and the
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