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10.3 Change-rate limit
10.3.1
Outline of change-rate limit function
In the event of a sudden change in the density or a sudden variation in the output due to intrusion by
bubbles, etc., this function is used to exclude these signals to restrain the sudden output change. By
setting two measurement conditions of permissible variation width and limit times, the conditions for
change-rate limit are set.
It is possible to set 0.00 to 9.99(%TS) as the permissible variation width and 0 to 99 times as the
limit times. Setting the limit times to zero means that no change-rate limit is imposed.
10.3.2
Examples of operating the change-rate limit function
The change-rate limit function is described with examples below.
<Setting conditions>
The setting conditions shall be as follows.
* Width of change-rate limit function: 0.5%TS
* Times of change-rate limit function: Twice
The conditions that are set as above mean the following.
① All the variations within 0.5%TS are permitted and output without modification.
② Variations exceeding 0.5%TS are limited up to twice, outputting the immediately preceding
signal in place of the relevant signals.
③ Variations in excess of 0.5%TS which continue three times are judged to be signal variations
resulting from actual density variations, thus outputting the 3rd signal without modification.
Example 1: Operation for temporary and sudden signal variation
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1
2
3
4
Fig.10.3.1 Original Signal
Fig.10.3.1 shows the original signal before the change-rate limit is processed. No.1 to No.4 are
varying within a small width; however, only signals No.5 and No.6 are varying in excess of 0.5%TS
deviation from the immediately preceding signal No.4. No.7 to No.10 are back to a small width of
variation.
In the event that the above-set change-rate limit is applied to such signals, the output signals are as
shown in Fig.10.3.2. Since signals No.5 and No.6 are varying in excess of 0.5%TS with regard to
signal No.4, signal No.4 is output instead with regard to No.5 and No.6. Signal No.7 is output
without modification. Signals No.8 to No.10, which are also within the variation width of 0.5%TS
with regard to the respective immediately preceding signals, are output without modification.
5
6
7
8
9
10
Signal No..
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1
2
3
Fig.10.3.2 Output Signal After Variation Factor
84
4
5
6
7
8
9
Signal No..
Restriction
10
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