Watlow CLS - Manual (Page 174)

Glossary
166
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.
Frequency
The number of cycles over a specified period of
time, usually measured in cycles per second. Also
referred to as Hertz (Hz). The reciprocal is called
the period.
G
Gain
The amount of amplification used in an electrical
circuit. Gain can also refer to the Proportional (P)
mode of PID.
Global Alarm
Alarm associated with a global digital output that
is cleared directly from a controller or through a
user interface.
Global Digital Outputs
A pre-selected digital output for each specific
alarm that alerts the operator to shut down critical
processes when an alarm condition occurs.
Ground
An electrical line with the same electrical poten-
tial as the surrounding earth. Electrical systems
are usually grounded to protect people and equip-
ment from shocks due to malfunctions. Also
referred to a "safety ground".
H
Hertz(Hz)
Frequency, measured in cycles per second.
High Deviation Alarm
Warns that the process is above setpoint, but
below the high process variable. It can be used as
either an alarm or control function.
High Power
Any voltage above 24 VAC or Vdc and any cur-
rent level above 50 mAac or mAdc.
High Process Alarm
A signal that is tied to a set maximum value that
can be used as either an alarm or control function.
High Process Variable (PV)
See Process Variable (PV).
High Reading
An input level that corresponds to the high pro-
cess value. For linear inputs, the high reading is a
percentage of the full scale input range. For pulse
inputs, the high reading is expressed in cycles per
second (Hz).
I
Infrared
A region of the electromagnetic spectrum with
wavelengths ranging from one to 1,000 microns.
These wavelengths are most suited for radiant
heating and infrared (noncontact) temperature
sensing.
Input
Process variable information that is supplied to
the instrument.
Input Scaling
The ability to scale input readings (readings in
percent of full scale) to the engineering units of
the process variable.