3-7
On-line Operations
NOTE
Selecting Not Used from the Meter Type screen will disable the meter.
3. Select Send to download the new meter configuration to the
transmitter.
For a more detailed description of the meter features and diagnostic
messages, refer to “LCD Meter (Option Code M5)” on page 6-6.
Alarm Values
(1)
The Alarm Values command allows the high and low alarm and
saturation values to be viewed. Transmitters are factory configured for
either Rosemount standard or NAMUR-compliant output levels and
cannot be changed in the field. Use the failure mode jumper (see
“Failure Mode and Security Jumpers” on page 2-7) to set whether the
output will be driven to high alarm or low alarm in the case of failure.
Process Variable Damping The PV Damp command 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 your system. The default damping value is 5.0 seconds
and can be reset to any value between 0 and 32 seconds.
The value chosen for damping affects the response time of the
transmitter. When set to zero (i.e., disabled), the damping function is off
and the transmitter output reacts to changes in input as quickly as the
intermittent sensor algorithm allows (refer to “Intermittent Sensor
Algorithm” on page 5-14). Increasing the damping value increases
transmitter response time.
With damping enabled, if the temperature change is within 2 percent of
the output range, the transmitter measures the change in input every
500 milliseconds and outputs values according to the following
relationship:
At the value to which the damping time constant is set, the transmitter
output is at 63 percent of the input change; it continues to approach the
input according to the damping equation above.
For example, as illustrated in Figure 3-1, if the temperature undergoes
a step change—within 2 percent of the output range—from 100 degrees
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.
For information regarding the damping function when the input change
is greater than 2 percent of the output range, refer to “Intermittent
Sensor Algorithm” on page 5-14.
HART Fast Keys 1,4,3,4
(1) This command is not available in previous versions of the Model 3144 and 3244MV transmitters.
HART Fast Keys 1,3,3
Damped Value P N–()
2TU–
2TU+
------------------
× N+=
P =previous damped value
N =new sensor value
T = damping time constant
U =update rate
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