D8 Series User’s Guide
164
Emissivity
The ratio of radiation emitted from a surface
compared to radiation emitted from a blackbody
at the same temperature.
Engineering Units
Selectable units of measure, such as degrees
Celsius or Fahrenheit, pounds per square inch,
newtons per meter, gallons per minute, liters per
minute, cubic feet per minute or cubic meters
per minute.
F
Fahrenheit
The temperature scale that sets the freezing
point of water at 32°F and its boiling point at
212°F at standard atmospheric pressure. The
formula for conversion to Celsius is:
°C = 5/9 (°F - 32).
Failed Sensor Alarm
Warns that an input sensor no longer produces
a valid signal.
Filter
Filters are used to handle various electrical
noise problems.
Digital Filter
— A filter that slows the
response of a system when inputs change
unrealistically 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 Filter
— A filter that slows the
change in the response of the heat or cool
output. 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
G
Gain
The amount of amplification used in an electrical
circuit. Gain can also refer to the proportional (P)
mode of PID.
Global Alarm
Warns that one or more alarm conditions exist
by activating a digital output.
Ground
An electrical line with the same electrical
potential as the surrounding earth. Electrical
systems are usually grounded to protect
people and equipment from shocks due
to malfunctions. Also referred to as “safety
ground.”
H
Hertz (Hz)
Frequency, measured in cycles per second.
High Deviation Alarm
Warns that the process has risen more than a
certain amount above set point. It can be used
as either an alarm or control function.
High Power
(As defined by Watlow) Any voltage above
24VAC or VDC and any current level above
50mA AC or mA DC.
High Alarm
A signal that is associated with a set maximum
value that can be used as either an alarm or
boost control function.
HMI
Human-machine interface.
Hysteresis
Control Hysteresis
— The range through
which a variation of the input produces
no noticeable change in the output. In the
hysteresis, specific conditions can be placed
on control output actions. Operators select
the hysteresis. It is usually above the heating
proportional band and below the cooling
proportional band.
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