Explanation Of Signal Processing Algorithm - Emerson Rosemount 8782 Reference Manual

Reference Manual
00809-0100-8782
Scan time
LOI menu path
This setting allows signal processing to scan the flow and provide a more stable output.
The default setting is 0.5 seconds; the range is 0 to 1.0 seconds. Setting Scan Time to zero
disables this feature.
• A shorter Scan Time can increase response time but may introduce more noise into the
flow reading.
• A longer Scan Time can decrease response time but may provide a more stable flow
reading.
Time limit
LOI menu path
The time limit parameter forces the output and running average values to the new value of
an actual flow rate change that is outside the percent limit boundaries. It thereby limits
response time to flow changes to the time limit value rather than the length of the running
average. If the average time is 10 seconds, then the response time of the system is 10
seconds. In some cases this may be unacceptable. Setting the time limit forces the
transmitter to clear the value of the running average and re-establish the output and
average at the new flow rate once the time limit has elapsed. This parameter limits the
response time added to the loop. A suggested time limit value of 2 seconds is a good
starting point for most applicable process fluids. This parameter can be configured for a
value between 0.6 and 256 seconds. The default value is 2 seconds.
10.5

Explanation of signal processing algorithm

An example plotting flow rate versus time is given below to help visualize the signal
processing algorithm.
Reference Manual
Detailed Setup → Signal Processing → Custom Config → Scan
Time
Detailed Setup → Signal Processing → Time Limit
Digital Signal Processing
November 2019
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