CD Automation Revo TC 2ph User Manual page 38

CD Automation srl
14.3.4 Action of alarm output.
(a s i dicated as "A ar
Whe a a ar status is ass ciated with the state f a physica
Qua d a stat di u a ar e : ass ciat
relationship between the alarm state and relay state.
Tw acti are p ssibi e6
1) Direct acti 6 ut '( whe the a ar
2) Riverse acti 6 'ut 'FF whe the a ar
Direct action is the most commonly used but you must remember that the reverse action allows to have an
alarm signal when the instrument does not work or is off(because the ON state of alarm is indicated by the
OFF state of output, when the instrument is switched off or not working the output will be definitely OFF)
In the case of relay output , the status of Output may not be sufficient to describe the state of the contact. In
fact, when the output relay is provided with changeover contacts it is clear that the choice of the normally
closed contact (NC) or normally open (NO) allows for equal status of the relay to reverse the state of the
contact.
H wever re ai s the c
i stru e t is switched ff r
14.3.5 Resetting of an Alarm
The a ar s we have see are based
a s g es 'FF aut
I s e cases it is preferab e that the a ar
i the 'FF > e the a ar
ther) I this case we say that the a ar
The reas f this ch ice is due to the level of danger of the anomaly reported from the alarm, an
overcurrent can damage the system and cause fire or dangerous situations for the users
Forcing the user to perform an action also ensures that we take note of the report and eliminate the cause of
the problem before resetting the system.
Alarms with manual reset may have different behaviors depending on different situations but, generally, one
can identify two families of behavior:
1) A ar with u c diti
Are those alarms that, when performed manually reset, set the alarm to OFF condition even if the alarm
condition is still present.
A typical example are the alarms that drive the sirens, once the user reaches the machinery switch off the
siren and then performs the necessary actions to remove the alarm condition. To get a further alarm signal is
necessary that the measure goes to the area OFF and back in the ON area.
Acti ")
is '( (ex 6 excited re ay whe the a ar
is '( (ex 6 u #excited re ay whe the a ar
siderati s va id regardi g the p ssibi ity f havi g a a ar
t w r i g (reverse acti
the c
atica y. I these cases it is said that the a ar
wi retur t the 'FF c
has a
ed reset
utput (ex re ay)
stat di u uscita fisica (es re :) it's necessary to define the
)
cept that whe the
sti re ai s i the '( c
diti y after a physica acti
a ua reset
pag. 38 di 122
is '()
is '()
sig a whe the
easure fa s i the 'FF area the a ar
is equipped with aut
diti eve after the
(pressi g a ey r
atic reset
easure is bac