Watlow CLS200 - Manual (Page 234)

Glossary CLS200 Series User’s Guide
218 Watlow Anafaze Doc.# 0600-3050-2000
proportioning, distributed zero crossing, Serial
DAC or analog. Also the description of the elec-
trical hardware that makes up the output.
Overshoot
The amount by which a process variable
exceeds the setpoint before it stabilizes.
P
Panel Lock
A feature that prevents operation of the front
panel by unauthorized people.
PID
Proportional, Integral, Derivative. A control
status with three functions: Proportional
action dampens the system response, integral
corrects for droops, and derivative prevents
overshoot and undershoot.
Polarity
The electrical quality of having two opposite
poles, one positive and one negative. Polarity
determines the direction in which a current
tends to flow.
Process Variable (PV)
The parameter that is controlled or measured.
Typical examples are temperature, relative
humidity, pressure, flow, fluid level, events, etc.
The high process variable is the highest value
of the process range, expressed in engineering
units. The low process variable is the lowest
value of the process range.
Proportional (P)
Output effort proportional to the error from
setpoint. For example, if the proportional band
is 20˚ and the process is 10˚ below the setpoint,
the heat proportioned effort is 50%. The lower
the PB value, the higher the gain.
Proportional Band (PB)
A range in which the proportioning function of
the control is active. Expressed in units,
degrees or percent of span. See also PID.
Proportional Control
A control using only the P (proportional) value
of PID control.
Pulse Input
Digital pulse signals from devices, such as
optical encoders.
R
Ramp
A programmed increase in the temperature of
a setpoint system.
Range
The area between two limits in which a quan-
tity or value is measured. It is usually
described in terms of lower and upper limits.
Recipe
See Job.
Reflection Compensation Mode
A control feature that automatically corrects
the reading from a sensor.
Relay
A switching device.
Electromechanical Relay — A power
switching device that completes or inter-
rupts a circuit by physically moving electri-
cal contacts into contact with each other.
Not recommended for PID control.
Solid State Relay (SSR) — A switching
device with no moving parts that completes
or interrupts a circuit electrically.
Reset
Control action that automatically eliminates
offset or droop between setpoint and actual
process temperature. See also 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.
Resistance
Opposition to the flow of electric current, mea-
sured in ohms.
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 tempera-
ture coefficient sensor only, while the ther-
mistor can have either a negative or positive