BE1-951
BESTlogic Programmable Logic
7-11
OUT1 through OUT5 have normally open contacts (coil is de-energized). Normally open contacts can be
used as normally closed outputs by inverting the logic expressions that drive them. Inverting an output logic
expression causes the coil to be energized with the contacts closed in the normal state. Caution should be
taken with normally closed contact logic because there are no shorting bars to maintain the closed condition
if the draw-out assembly is removed from the chassis. In applications where a normally closed output is
needed even when the electronics are removed, a normally open contact from the relay can be used to drive
a low-cost auxiliary relay. The normally closed output of the auxiliary relay will maintain the closed output
when the draw-out assembly is removed from the case. Alternately, an external switch can be used to short
across a normally closed relay output when the draw-out assembly is removed. Extra care is required to
ensure that the switch is closed prior to removing the draw-out assembly and that the switch is open after
the relay is placed back in service.
Several links between the programmable alarms function and BESTlogic programmable logic allow alarm
functions to be used in a logic scheme and programmable logic functions to be used in the alarm reporting
function.
Programmable alarm settings for Major, Minor, and Logic alarms drive BESTlogic variables ALMMAJ,
ALMMIN, and ALMLGC. These variables can be used in logic expressions to control logic when an alarm
is active.
Virtual outputs VO13, VO14, and VO15 are driven by BESTlogic expressions. These three logic variables
are also available in the programmable alarm function. Virtual outputs can also be assigned user
programmable labels (described previously). With this feature, a logic condition can be designed and used
for an alarm. The virtual output label would then be reported in the alarm reporting function.
