West Control Solutions MRC 7000 Controller Manual - Manual (Page 67)

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Pen Action on Power Up
This parameter specifies whether the pen, on a power-up will drive to the "Home Position"
(center of chart), then return to its correct postion. This is done as a cal check. Settings are
0=go to "home" and 1=remain in last position prior to power down. Default is 0.
Platen
The flat surface in the instrument upon which the chart rotates.
Position Proportioning Sensitivity
A percentage of the first output proportional band width (Pb1).
Process Filter Factor
This parameter is adjustable from 1 to 20 which represents the number of scans per second
of the process variable that are averaged together before updating the process value used for
control purposes. The factory default value is 1 = no filtering. Display code PFF.
Process Retransmission Output
Allows re-transmission of the process variable. Factory default is 0 = not selected. Display
code Pout. If selected, must be assigned to a current output and scaled using Process Output
upper and lower values.
Process Output Upper and Lower Values
(Used in conjunction with process retransmission output)
These parameters specify the process value range over which the assigned current output will
vary in a linear manner from 100% to 0%. If the process value is greater than Pou the output
will be 100%. If the process value is less than PoL the output will be 0%. Factory default
values are 2000 for the upper value and 0 for the lower value. Display codes Pou (upper) and
PoL (lower).
Process Rounding
This parameter is adjustable from 0 to 100 units and is used to round the process value to the
nearest value specified. This is for display only and does not affect the recorded value or
control action. Intended for use where the engineering units span is large, to reduce display
fluctuation. Factory default is 0 = no rounding. Display code Prnd. (e.g. Prnd = 3, Process
Value = -6, -3, 0, 3, 6, 9....)
Proportional Band (PB)
This parameter is adjustable from 1 to 3000 units (not Percent of span) and represents the
process value range where the proportional output is at a percentage of the full output.
Instructions for determining Pb are given in Section 4.3 (page 42) . Factory default is 100
units. Display code Pb1 and Pb2.
Rate (Derivative)
This parameter is adjustable from 0.0 to 10.0 minutes and specifies how the control action
responds to the rate of change in the process variable. For example, if the process variable is
rising rapidly to setpoint, power is turned off sooner than it would be if the rise were slow. In
effect, derivative action anticipates lags within the system and shifts the proportioning band by
an amount determined by the rate of change of the input sensor.
Magnitude of the shift is determined by a derivative time constant. If the time constant is, say,
.1 minute (6 seconds), for every unit per second rate of change of the process variable at the
sensor, the proportiong band is moved 7 units in the direction that helps control. Likewise, if
the time constant is 1 minute (60 seconds), for every unit per second rate of change of the
process variable at the sensor, the proportioning band is moved 60 units in the direction that
helps control. Factory default is 0.0 Display code rAtE.
Second Output Position (SoP)
This parameter is adjustable from -1000 to 1000 units and represents a shift or offset of the
on-off actuation points or proportional band for the second output relative to the normal
position. A positive value creates a gap where no control outputs are on, a negative value
creates an overlap of control outputs (if the first output position is at the normal position).
Second Output Position also shifts the proportional band with respect to the process value
range outside of which integral action is highlighted (reset-windup inhibit). Factory default is 0.
Display code SoP.