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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 proportion-
ing 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.
Setpoint Re-transmission Output (EA Software Option)
This parameter allows for a linear milliamp output relative to the setpoint value. The current
output may be scaled over a range selectable by the user. This output can be used as a
manual setting station.
Spread (Second Output Position)
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 SPrd.
Setpoint Ramp Rate
This Program mode parameter provides a rate of change control of the instrument setpoint
value. This parameter is used to inhibit sudden upsets in the instrument control caused by
large setpoint changes. This feature also creates a soft start when the instrument power is
turned on. The instrument will read the process value at the time the power was turned on as
the setpoint value. A rate of change ramp will change the internal setpoint to the setpoint
seen by the instrument at the time the power was turned off.
