West Control Solutions Pro-EC44 - Manual (Page 221)

Pro-EC44 2-Loop Graphical Profile Controller & Recorder
Pro-EC44 Product Manual - 59540-1 October 2013 Page 214
Integral
Time
Power
Response
begins to control
deviation step
Time
Indicator
An instrument that displays process values, but lacks control features. Typically, alarm
outputs are available that will activate at pre-set PV values.
Also refer to: Controller; Limit Controller and Process Variable.
Input Configuration
A sub-menu of configuration mode, used to adjust the parameters that relate to the process
and auxiliary inputs (type, engineering units, decimal places, scaling, filtering etc.).
Also refer to: Auxiliary Input; Configuration Mode and Process Input.
Input Filter Time Constant
This parameter is used to filter out extraneous impulses affecting process variable values.
The filtered PV is used for all PV dependent functions (display, control, alarm etc). Use this
parameter with care as it will also slow the response to genuine process changes.
Also refer to: Process Variable.
Input Range
This is the overall process variable input range and type as selected by the Process Input
Type parameter. This range can be scaled using the Scale Input Upper & Lower Limits.
Also refer to: Input Span; Process Input; Scaled Input Lower Limit and Scaled Input Upper
Limit.
Input Span
The measuring and display limits, as defined by the Scale Input Lower and Scaled Input
Upper Limits. The trimmed span value is also used as the basis for calculations that relate to
the span of the instrument (e.g. proportional bands).
Also refer to: Input Range; LSD; Primary Proportional Band; Scaled Input Lower Limit;
Scaled Input Upper Limit and Secondary Proportional Band.
Integral Action
Integral action biases the proportional control output to compensate for process load
variations. Their combined values adjust the correcting variable, until the control deviation
error is zero, at which point the integral value is held constant. Decreasing the integral time
constant increases the integral action. Integral action is also known as “Automatic Reset”.
The time constant is defined as the interval in which
the part of the output due to integral action increases
by an amount equal to the part of the output due to
the proportional action, when the control deviation is
unchanging*. For example, if a step change is made
in the PV, the output immediately changes due to
proportional action. The deviation error is integrated
over time, steadily changing the integral output. The
time it takes for integral power to change by the
same amount due to proportional action (I% = P%)
is the “reset”, or integral time. *For the purpose of
the definition, the power output change does not affect the PV (in reality it would begin
correcting the control error). Integral must be set to OFF if PD control is required, and it is not
available if the primary output is set to On-Off.
Also refer to: Control Deviation; On-Off Control; PD Control; PI Control; PID; PID Sets;
Primary Proportional Band; Secondary Proportional Band; Derivative Action; and Tuning.