BERTHOLD TECHNOLOGIES LB 444 - Automatic Measuring Time Switchover; Figure 28: Response

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8.3 Automatic Measuring Time Switchover
To quickly update the measured value if sudden density changes occur, you can enable
automatic measuring time switchover (rapid switchover in the Parameter menu, see page
20).
The smallest value that can be entered is 8 s.
If a sudden density change occurs which exceeds the entered threshold (Sigma), the en-
tered time constant is reduced to 1/10 of the original value, but not less than 0.8 s.
Thus, the output signal adjusts much quicker to the new density value. The changed time
response of the output signal is illustrated in the diagram below.
Response
-3 2 7 12 17 22 27 32 37 42 47 52 57 62 67 72 77 82 87 92 97
0
20
40
60
80
100
T in s
Display and output signal in %
1 Density value
2 Signal trend with
3 Signal trend without
automatic switchover
of time constant
Figure 28: Response
When rapid switchover is in effect, the measurement first works with the defined basic
time constant. If sudden density changes occur which exceed the Sigma band, the sys-
tem switches to 1/10 of the time constant and reading and output signal can follow the
density change much quicker. At the same time, statistical variations increase by a factor
of about 3. When the density value becomes stable again, the system automatically
switches back to the longer basic time constant after a time period that corresponds to
the basic time constant.