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DCP200 Profile Controller & Recorder - Product Manual
Page 162 Glossary 51-52-25-150, Issue 1 – April 2009
Solenoid Valve
An electromechanical device, use to control the flow of gases or liquids. It has just two
states, open or closed. Usually, a spring holds the valve closed until a current is passed
through the solenoid coil forces it open. Standard process controllers with time-proportioned
or On-Off outputs can be used to control these types of valves.
Solenoid valves are often used with high/low flame gas burners. A bypass supplies some gas
at all times, but not enough to heat the process more than a nominal amount (low flame). A
controller output opens the solenoid valve when the process requires additional heat (high
flame).
Also refer to: Modulating Valves, On-Off Control and Time Proportioning Control.
Supervisor Mode
Supervisor Mode allows access to a lock code protected sub-set of the main configuration
parameters. The unlock code is different from the higher level Configuration Menu unlock
code. Up to 50 Configuration Menu parameters can be chosen for inclusion in Supervisor
Mode using the PC configuration software. If none have been chosen, this mode is disabled.
Refer to the Supervisor Mode information in the Configuration & Use section.
Also refer to: Configuration Menu and Lock Codes
Thermocouple
A temperature sensor made from two different metals. They convert temperature difference
between their cold junction (the measuring instrument) and the hot junction, into a small
signal or a few microvolts per °C. Thermocouples are cheap and interchangeable, but the
wires and connectors used must match the metals used in their construction. They can
measure a wide range of temperatures; some thermocouples can withstand very high
temperatures such as furnaces. The main limitation of thermocouples is accuracy.
The temperature measured by the thermocouple can be displayed as °C; °F or °K.
The colour codes for the common types are shown in the Thermocouple Wire Identification
Chart in the Electrical Installation Section of this manual.
Also refer to: Engineering Units, Input Range, Process Input and RTD.
Three Point Stepping Control
Modulating valves normally require a special “Three Point Stepping” control algorithm. This
which provides an output to move the valve further open, or further closed whenever there is
a control deviation error. When this error is zero, no further output is required to maintain
control unless load conditions change. This type of controller is often called a Valve Motor
Drive controller. This instrument does not currently have a three point stepping algorithm.
However, modulating valves that have a valve positioning circuitry to adjust the valve position
from a DC linear mA or voltage output signal can be controlled.
Also refer to: Control Deviation, Linear Output, Modulating Valve, and Valve Motor Control