Watlow PPC-2000 - Manual (Page 314)

Glossary PPC-2000 User’s Guide
286 Watlow Anafaze Doc.# 30002-00 Rev 2.3
Custom Linear Input
A user-defined process input that represents a
straight line function.
D
Deadband
The range through which a variation of the input
produces no noticeable change in the output. In
the deadband, specific conditions can be placed
on control output actions. Operators select the
deadband. It is usually above the heating propor-
tional band and below the cooling proportional
band.
Default Parameters
The programmed instructions that are perma-
nently stored in the microprocessor software.
Derivative Control (D)
The last term in the PID algorithm. Action that
anticipated the rate of change of the process, and
compensates to minimize overshoot and under-
shoot. Derivative control is an instantaneous
change of the control output in the same direction
as the proportional error. This is caused by a
change in the process variable (PV) that
decreases over the time of the derivative (TD).
The TD is in units of seconds.
Deviation Alarm
Warns that a process has exceeded or fallen
below a certain range around the setpoint.
Digital to Analog Converter (DAC)
A device that converts a numerical input signal to
a signal that is proportional to the input in some
way.
Digital I/O
I/O that interfaces to 2 state field devices such
limit switches or solid state relays.
DIN (Deutsche Industrial Norms)
A set of technical, scientific and dimensional
standards developed in Germany. Many DIN
standards have worldwide recognition.
Dip Switch
A set of compact toggle switches used to config-
ure electronic hardware. The toggle switches are
housed in a Dual In-line Package.
Distributed Zero Crossing (DZC)
A form of digital output control. Similar to burst
fire.
E
Electromagnetic Interference (EMI)
Electrical and magnetic noise imposed on a sys-
tem. There are many possible causes, such as
switching ac power on inside the sine wave. EMI
can interfere with the operation of controls and
other devices.
Engineering Units
Selectable units of measure, such as degrees Cel-
sius and Fahrenheit, pounds per square inch,
Newtons per meter, gallons per minute, liters per
minute, cubic feet per minute or cubic meters per
minute.
EPROM
Erasable Programmable, Read-Only Memory
inside the controller.
F
Failed Sensor Alarm
Warns that an input sensor no longer produces a
valid signal. For example, when there are thermo-
couple breaks, infrared problems or resistance
temperature detector (RTD) open or short fail-
ures.
Filter
Filters are used to handle various electrical noise
problems.
Digital Filter (DF) — A filter that allows the
response of a system when inputs change unreal-
istically or too fast. Equivalent to a standard
resistor-capacitor (RC) filter
Digital Adaptive Filter — A filter that rejects
high frequency input signal noise (noise spikes).
Heat/Cool Output Filter — A filter that slows
the change in the response of the heat or cool out-
put. The output responds to a step change by
going to approximately 2/3 its final value within
the numbers of scans that are set.