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3.0
2.5
2.0
1.5
1.0
0.5
0.0
1
2
3
Fig.10.3.3 Original Signal
Fig.10.3.3 shows the original signal before the change-rate limit is processed. The numeric values
along the horizontal axis refer to the signal numbers. No.1 to No.4 are varying within a small width;
however, signal No.5 is varying in excess of 0.5%TS with No.6 to No.10 remaining in a state not
very different from No.5.
In the event that the above-set change-rate limit is applied to such signals, the output signals are as
shown in Fig.10.3.4. 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.
Signals No.7 to No.10, which are within the variation width of 0.5%TS with regard to the
respective immediately preceding signals, are output without modification.
10.3.3
Cautions in using the change-rate limit factor
(1) Setting the change-rate limit width
The value can be set within the range of 0.00%TS to 9.99%TS. If the width is set to as little a
value as the normally indicated deflection width, restricted signals will increase and indications
will vary in the shape of steps. Therefore, set a sufficiently large value so that the variation
width is reliably judged to be in error.
(2) Setting the times of change-rate limit
Signals that are made faulty due to intrusion of large bubbles, etc. may affect two neighboring
signals in relation to measurement timing. Therefore, although the change-rate limit has an
effect even when it is applied only once, it is desirable to set the times of change-rate limit at
least to two times in order to reliably exclude error signals. In the event of density variations in
the shape of steps as shown in Example 2, a delay increases in accordance with the set times.
Set an appropriate value for the times in accordance with the responsiveness required of the
plant.
Example 2: Signal change in the shape of steps
4
5
6
7
8
9
Signal No.
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1
2
10
Fig.10.3.4 Output Signal After change-rate limit
85
6 F 8 A 0 5 2 1
3
4
5
6
7
8
Signal No.
9
10
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