Watlow CAS200 - Manual (Page 122)

Glossary CAS200 User’s Guide
110 Watlow Anafaze
Output Type
The form of PID control output, such as Time
Proportioning, Distributed Zero Crossing,
SDAC, or Analog. Also the description of the
electrical 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
mode 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
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 20º and the process is 10º 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 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 interrupts a
circuit by physically moving electrical 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.
Automatic Power Reset — A feature in
latching limit controls that
Resistance
Opposition to the flow of electric current, mea-
sured in ohms.