Filter
Top Products
134
Reference Manual
00809-0100-4444, Rev AC
Section 7: Digital Signal Processing
January 2015
Digital Signal Processing
Time limit
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 number of samples selected is 100, then the response time of the system is 10 seconds. In
some cases this may be unacceptable. Setting the time limit forces the 8732EM 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 two 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.
7.6 Explanation of signal processing algorithm
An example plotting flow rate versus time is given below to help visualize the signal processing
algorithm.
Figure 7-1. Signal Processing Functionality
X: Input flow signal from sensor.
O: Average flow signals and transmitter output, determined by the number of samples
parameter.
Tolerance band, determined by the percent limit parameter.
- Upper value = average flow + [(percent limit/100) average flow]
- Lower value = average flow - [(percent limit/100) average flow]
LOI menu path
Device Setup, Detailed Setup, Signal Processing, Main Config DSP, Time Limit
Traditional fast keys
1,4,4,2,4
Device dashboard 2,2,8,6,4
Flow
Rate
Max
%
Limit
Time Limit
10 Samples = 1
Second
Time