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DCP200 Profile Controller & Recorder - Product Manual
51-52-25-150, Issue 1 – April 2009 Glossary Page 163
Time Proportioning Control
Time proportioning control is accomplished by cycling the output on and off during the
prescribed cycle time, whenever the process variable is within the proportional band(s). The
PID control algorithm determines the ratio of time (on vs. off) to achieve the level of the
correcting variable required to remove the control deviation error. E.g. for a 32 second cycle
time, 25% power would result in the output turning on for 8 seconds, then off to 24 seconds.
This type of output might be used with electrical contactors, solid state relays or solenoid
valves. Time proportioning control can be implemented with Relay, Triac or SSR Driver
outputs for either primary or secondary outputs.
Also refer to: Control Deviation, Correcting Variable, Current Proportioning Control, Cycle
Time, PID, Primary Proportional Band, Relay, Secondary Proportional Band, Solenoid Valve,
SSR and Triac.
Trend Display
Trend View is a graphical representation of recent process conditions. This feature is
available on all variants. It does not rely on the Data Recorder option, and does not retain the
stored data if the power is turned off. The trend shows the most recent 120 out of 240 stored
data points. Its scale adjusts automatically for the best resolution for the visible data. This
data can be the process variable; process variable & setpoint (shown as a doted line), or the
minimum and maximum value of the process variable measured since the last sample. Any
active alarm(s) are indicated above the graph. The user can scroll the right hand cursor line
back to examine all 240 data points. The sample interval and data to display is set in Display
Configuration.
Also refer to: Alarm Types, Display Configuration, Operation Mode, and Process Variable,
Setpoint.
Tuning
PID Controllers must be tuned to the process in order for them to attain the optimum level of
control. Adjustment is made to the tuning terms either manually, or by utilising the controller’s
automatic tuning facilities. Tuning is not required if the controller is configured for On-Off
Control.
Also refer to: Auto Pre-Tune, Controller, Derivative Action, Integral Action, On-Off control,
PID, Pre-Tune, Primary Proportional Band, Self-Tune, Secondary Proportional Band and
Tuning Menu.
Tuning Menu
The Tuning Menu can be accessed from the Main Menu. This menu is lock code protected.
It gives access to the Pre-tune, Auto Pre-Tune and Self-tune facilities. These assist with PID
tuning, by setting up Proportional band(s), Integral and Derivative parameter values. Tuning
is not required for On-Off control.
Pre-tune can be used to set PID parameters approximately. Self-tune may then be used to
optimise the tuning if required. Pre-tune can be set to run automatically after every power-up
by enabling Auto Pre-Tune.
Refer to the Automatic Tuning information in the Configuration & Use section.
Also refer to: Auto Pre-Tune, Derivative Action, Integral Action, Lock Codes, Main Menu, On-
Off control, PID, Pre-Tune, Primary Proportional Band, Self-Tune, Secondary Proportional
Band and Tuning Menu.