Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 399)

D-1 Publication 900-UM007D-EN-E - January 2011
Appendix
D
Glossary
Adaptive Tuning: Used to continuously monitor and optimize PID constants
while the controller operates. Three tuning algorithms are used to recalculate
the PID constants within 500 ms after the process value stabilizes at set point:
step-response method, disturbance tuning, and hunting tuning.
Anti-Reset Wind-Up (ARW): A feature of PID controllers that prevents the
integral (auto-reset) circuit from operating when the temperature is outside the
proportional band.
Alpha (
α): This represents the temperature coefficient of the change in
electrical resistance of a material. For each °C in temperature the electrical
resistance changes. It is the defining parameter for platinum resistance
temperature detectors (RTD sensors). The unit of measure is ohms/ohms/°C.
Analog: Data collected and represented by continuously variable quantities,
such as voltage measurement or temperature variation.
Auto-Tuning: This feature automatically calculates then resets the PID values
based on temperature control performance over a sampled period. In some of
the controllers, auto-tuning also optimizes the settings for fuzzy logic control
values.
CE: A marking on products that comply with European Union requirements
pertaining to safety and electromagnetic compatibility.
Celsius: A temperature scale in which water freezes at 0°C and boils at 100°C
at standard atmospheric pressure. The formula to convert Fahrenheit
temperatures to Celsius is as follows: °F = (1.8 x °C) +32.
Cold Junction Compensation: Electronic means of compensating for the
ambient temperature at the cold junction of a thermocouple so it maintains a
reference to 0°C.