Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B User Manual
Page 402
Publication 900-UM007D-EN-E - January 2011
D-4
Glossary
Fuzzy Logic:
A rule-based control algorithm that enables control devices to
make subjective judgments in a way similar to human decision-making. Within
a process controller, fuzzy logic uses some basic information about the system,
which is input by the user, to emulate the way an expert operator who was
manually controlling the system would react to a process up set.
Heat Sink:
An object that conducts and dissipates heat away from an object in
contact with it. Solid-state relays usually use a finned aluminum heat sink to
dissipate heat.
Hot Junction and Cold Junction:
If a thermocouple is generating a voltage,
this means that there is a temperature difference between the two ends of the
thermocouple. The hot end is the one that makes contact with the temperature
process being controlled. The cold end is at the sensor input terminals.
Hunting:
Oscillation of the process temperature between the set point and
the process variable. Derivative control is used in the control algorithm to
reduce hunting.
Hysteresis (Dead Band):
A temperature band between the ON and OFF of
an output in the ON/OFF control action. No heating or cooling takes place.
The band occurs between the ON and OFF points.
Infrared:
The portion of the electromagnetic spectrum with wavelengths
ranging from one to 1000 microns. These wavelengths are ideal for radiant
heating and non-contact temperature sensing.
Input Digital Filter:
A device used to sample the input slower than the scan
rate to allow the controller to monitor an input that changes very rapidly and
still have sufficient information from the process to control it.
Input Scaling:
The ability to scale input readings (% of full scale) to the
engineering units of the process variable.
Input Type:
The type of device used to provide a signal of temperature
change. These include thermocouples, RTDs, linear or process current, or
voltage inputs.
Integral Action (I):
Control action that eliminates offset, or droop, between
set point and actual process temperature. This is the “I” in the PID control
algorithm.
Japanese Industrial Standards (JIS):
A Japanese agency that establishes and
maintains standards for equipment and components. Its function is similar to
Germany’s Deutsches Institut für Normung.
Linearity:
A measure of the deviation of an instrument’s response from a
straight line.