Manual

14 WATLOW Series 365 User’s Manual
Glossary
Switching Sensitivity or Differential - In a heat-
ing application, the output will de-energize when
the actual temperature reaches the set point tem-
perature. The switching sensitivity or differential is
the drop in temperature required to re-energize the
output.
Temperature Droop - Phenomenon that occurs in
a proportional control system without reset. As the
proportional band is increased, the average
process temperature may drop to a point that is
not the set point temperature. This action takes
place even though the load has stabilized.
Temperature Oscillation or Hunting - Occurs
when the proportional band is too narrow or the
system is upset by some outside source. The
actual process temperature is not controlled within
the proportional band on its extreme temperature
excursions.
Load temperature may never stabilize. Control is
either full ON or full OFF, not within the proportion-
al band.
Zero Switching - Load is activated only during the
time period that the sine wave is going through
zero. This eliminates RFI and EMI radiation.
Applies to solid state outputs only.
or - Musical notes are used to alert you to
important details.
The Warning symbol (lightning bolt)
alerts you to a “WARNING”, a safety hazard which
could affect you and the equipment.
The Caution symbol (exclamation
point) alerts you to a “CAUTION”, a safety or func-
tional hazard which could affect your equipment or
its performance.
Automatic Reset (Integral) - Used in proportional
control systems to automatically pick up any sys-
tem droop. This action may be adjustable or fixed,
and adjusts the output level to obtain agreement
between actual process temperature and controller
set point.
Automatic Reset on Power Loss - The limit con-
trol does not recognize the power outage as a limit
condition. When power is restored, the output will
energize automatically as long as a temperature
limit condition does not exist.
Anti Reset - Inhibits reset action when the actual
process temperature is outside the proportional
band.
Cycle Time - Time interval between consecutive
turn ons.
ON/OFF - In a heating application, the output is
turned full ON below set point and stays turned on
until the process temperature reaches set point,
then the controller turns the output full OFF. At
this point, depending on the design of the thermal
system, the process temperature overshoots the
set point temperature by some degree. As the
load cools down below set point (an amount equal
to the switching sensitivity or differential) the out-
put is once again turned full ON.
Proportional Band - In a straight time proportional
control system when the actual process tempera-
ture is below set point and outside the proportional
band limit, 100% power is applied to the load.
When the actual process temperature is above set
point and outside the proportional band limit, 0%
power is applied to the load.
When the actual process temperature is within the
proportional band, the controller will proportion the
amount of power applied to the load, 0 to 100%.