Watlow Electric Micro-Based Autotuning Control SERIES 980/985 - Manual (Page 44)

Alarm: A condition, generated by a controller,
Droop: Difference in temperature between set
indicating that the process has exceeded or fallen
point and stabilized process temperature.
below the set or limit point.
Duty cycle: Percentage of “load ON time”
Anti-reset: Control feature that inhibits auto-
matic reset action outside of the proportional
band.
Automatic prompts: Data entry points where a
microprocessor-based control “prompts” or asks
the operator/programmer for information input.
Bumpless transfer: When transferring from
auto to manual operation, the control output(s)
will not change (“bumpless,” smooth transition).
Closed loop: Control system that has a sensing
device for process variable feedback.
Cold junction: Point of connection between
thermocouple metals and the electronic instru-
ment.
Cold junction
compensation: Electronic means used to
compensate for the effect of temperature at the
cold junction.
relative to total cycle time.
Hysteresis: In ON/OFF control, the temperature
change necessary to change the output from full
ON to full OFF.
Hunting: Oscillation or fluctuation of process
temperature between set point and process
variable.
input: Process variable information being sup-
plied to the instrument.
integral: Control action that automatically elimi-
nates offset, or “droop”, between set point and
actual process temperature. Also “reset.”
Isolation: Electrical separation of sensor from
high voltage circuitry. Allows for application of
grounded or ungrounded sensing element.
JIS: Japanese Industrial Standards. Also Japa-
nese Industrial Standards Committee (JISC).
Establishes standards on equipment and compo-
nents.
Cycle time: The time necessary to complete a
full ON-through-OFF period in a time proportion-
ing control system.
Dead band: A temperature band between
heating and cooling functions.
Offset: Adjustment to actual input temperature
and to the temperature values the Series 985
uses for display and control.
Derivative: Anticipatory action that senses the
rate of change of temperature, and compensates
to minimize overshoot and undershoot. Also
ON/OFF control: Control of temperature about a
set point by turning the output full ON below set
point and full OFF above set point in the heat
“rate.”
I
mode.
Deviation: The difference between the value of
the controlled variable and the value at which it is
being controlled.
Default parameters: The parameters, or pro-
grammed instructions, which are permanently
stored in microprocessor software to provide a
data base.
DIN: Deutsche Industrial Norms, a widely-
recognized German standard for engineering
units.
Display capability: In a digital indicating instru-
ment, the entire span that can be indicated if fully
utilized.
Open loop: Control system with no sensory
feedback. The Series 980/985 uses closed loop.
Output: Action in response to difference between
set point and process variable.
Overshoot: Condition where temperature
exceeds setpoint due to initial power up or
1 process changes.
P control: Proportioning control.
Parameter: A physical property whose value
determines the response of an electronic control
to given inputs.
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WATLOW Series 980/985 User’s Manual
Appendix