K-Patents PR-21-S - Manual (Page 53)

6 Configuration and calibration 47
For example, if the tolerance time is set to 10 seconds, and wash hold becomes
active after 7 seconds, the remaining tolerance time will be reset to 10 seconds
After the wash is over, there is still 10 seconds of tolerace time remaining.
6.2.6 Hold and signal damping
The signal filtering (damping) is stopped during hold. The last filtered value is
shown on the screen and set to the mA output (if the concentration output is con-
figured). Figure 6.5 illustrates this behaviour (gray areas represent the periods
when the hold is active).
0 50 100 150 200
Time [s]
40
42
44
46
48
50
52
54
56
58
60
CONC [%]
Original signal
Filtered (damped) output
Figure 6.5 Damping stops during hold
6.2.7 Hold functions with DD-23
The K-Patents Digital Divert Control System DD-23 uses the displayed concentra-
tion value in its decision logic. Due to this, the external hold functionality must not
be used with a DD-23, as it could potentially render the system unsafe by freezing
the measurement result.
The "hold during wash" must be used with DD-23. Otherwise the signal damp-
ing combined with low n
D
values caused by the wash process may give erroneous
information to the DD-23 after the wash is over.
The selection of tolerance time with DD-23 requires a careful risk analysis. The use
of the tolerance time functionality does not slow down the response of the instru-
ment when the instrument is in
NORMAL OPERATION . It does, however, slow down the
malfunction alarm in the DD-23 in case the process pipe becomes empty or some
other reason makes the optical image impossible to interpret. The recommended
value for tolerance time is 5 seconds when a DTR is used in a DD-23 system.