Watlow MICRODIN - Manual (Page 96)

A . 1 0 Wa t l o w M i c r o D I N
proportional control — A control using only the P (proportional) value of PID
control.
range — The area between two limits in which a quantity or value is measured.
It is usually described in terms of lower and upper limits.
rate — Anticipatory action that is based on the rate of temperature change, and
compensates to minimize overshoot and undershoot. See derivative.
rate band — A range in which the rate function of a controller is active.
Expressed in multiples of the proportional band. See PID.
reference junction — see junction, reference.
remote — A controller that receives its set point signal from another device
called the master.
remote set point — A signal that indicates the set point for the process, and is
sent from another device.
reset — Control action that automatically eliminates offset, or droop, between
set point and actual process temperature. Also see integral.
automatic reset — The integral function of a PI or PID temperature
controller that adjusts the process temperature to the set point after the system
stabilizes. The inverse of integral.
automatic power reset — A feature in latching limit controls that does not
recognize power outage as a limit condition. When power is restored, the output
is re-energized automatically, as long as the temperature is within limits.
manual reset — 1) A feature on a limit control that requires human
intervention to return the limit to normal operation after a limit condition has
occurred. 2) The adjustment of a proportional control to raise the proportional
band to compensate for droop.
resistance temperature detector (RTD) — A sensor that uses the resistance
temperature characteristic to measure temperature. There are two basic types
of RTDs: the wire RTD, which is usually made of platinum, and the thermistor,
which is made of a semiconductor material. The wire RTD is a positive
temperature coefficient sensor only, while the thermistor can have either a
negative or positive temperature coefficient.
RTD — See resistance temperature detector.
thermal system — A regulated environment that consists of a heat source,
heat transfer medium or load, sensing device and a control instrument.
thermocouple (t/c) — A temperature sensing device made by joining two
dissimilar metals. This junction produces an electrical voltage in proportion to
the difference in temperature between the hot junction (sensing junction) and
the lead wire connection to the instrument (cold junction).
thermocouple break protection — The ability of a control to detect a break
in the thermocouple circuit and take a predetermined action.
three-mode control — Proportioning control with integral (reset) and
derivative (rate). Also see PID.
time proportioning control — A method of controlling power by varying the
on/off duty cycle of an output. This variance is proportional to the difference
between the set point and the actual process temperature. Appendix