Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B User Manual
Page 405
Publication 900-UM007D-EN-E - January 2011
Glossary
D-7
Serial Communications:
A method of transmitting information between
devices by sending all bits serially over a communication channel. RS-232 is
used for point-to-point connections of a single device, usually over a short
distance. RS-485 communicates with multiple devices on a single, common
cable over longer distances.
Set Point:
The value configured on the process or temperature controller to
control the system.
Soft Start:
A method of applying power gradually over a period of seconds to
controlled devices such as heaters, pumps and motors. This lengthens the
service life of the load by limiting in-rush current to inductive loads.
Solid-State Relay (SSR):
A switching device with no moving parts that
completes or interrupts a circuit electrically.
Thermal Response:
The time required for the response curve of the
temperature sensor to rise to a specified percentage level (usually either 63% or
90%).
Thermocouple Sensor:
A device that converts heat to electricity. Usually
made of two wires, each of a different metal or alloy. The wires are joined at
one end, known as the hot end. The hot end makes thermal contact with the
process to be controlled. The cold end terminals are connected to the sensor
input. Voltages are created at both the hot and cold ends. The controller
measures the cold end temperature to determine the hot end temperature.
Underwriters Laboratories (UL):
This independent testing laboratory
establishes commercial and industrial standards, as well as tests and certifies
products in the US. They also offer testing to Canadian Standards Association
requirements with products bearing the cUL marking.
Undershoot:
This is the amount by which the process variable falls below the
set point before it stabilizes.
Zero Cross Switching:
Used in solid-state relays, this action provides output
switching only at or near the zero-voltage crossing point of the AC sine wave.
It reduces electromagnetic interference and high inrush currents during initial
turn-on.