Emerson Rosemount 644 Reference Manual page 34

Configuration
March 2021
Re-range the transmitter using LOI
Reference the image below to find the range value configuration path on the LOI.
Figure 2-14: Re-ranging the Transmitter with LOI
2.8.2 Damping
The damping function changes the response time of the transmitter to smooth variations
in output readings caused by rapid changes in input. Determine the appropriate damping
setting based on the necessary response time, signal stability, and other requirements of
the loop dynamics of the system. The default damping value is 5.0 seconds and can be
reset to any value between 1 and 32 seconds.
The value chosen for damping affects the response time of the transmitter. When set to
zero (disabled), the damping function is off and the transmitter output reacts to changes
in input as quickly as the intermittent sensor algorithm allows. Increasing the damping
value increases transmitter response time.
With damping enabled, if the temperature change is within 0.2 percent of the sensor
limits, the transmitter measures the change in input every 500 milliseconds (for a single
sensor device) and outputs values according to the following relationship:
P =
N =
T =
U =
At the value to which the damping time constant is set, the transmitter output is at 63
percent of the input change and it continues to approach the input according to the
damping equation above.
For example, as illustrated in
within 0.2 percent of the sensor limits—from 100 to 110 degrees, and the damping is set
to 5.0 seconds, the transmitter calculates and reports a new reading every 500
milliseconds using the damping equation. At 5.0 seconds, the transmitter outputs 106.3
degrees, or 63 percent of the input change, and the output continues to approach the
input curve according to the equation above.
34
VIEW CONFIG
SENSOR CONFIG
UNITS
RERANGE
LOOP TEST
DISPLAY
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EXIT MENU
Damped value = N − P x
previous damped value
new sensor value
damping time constant
update rate
Figure
ENTER VALUES
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EXIT MENU
2T − U
2T + U
2-15, if the temperature undergoes a step change—
Reference Manual
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LRV
URV
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+ P
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