K-Patents PR-21-S - Manual (Page 52)

46 PR-21-S instruction manual
e.g., NO SAMPLE , NO OPTICAL IMAGE , PRISM COATED ), the measurement is held for the given
number of seconds.
For example, a setting of 10 seconds ensures that any NO SAMPLE state which is
shorter that 10 seconds will not make a dip into the output signal. The factory
setting is 5 seconds, access the
6 TOLERANCE TIME menu item to set the tolerance time.
The tolerance time counter is reset always when there is a representative sample
on the prism (e.g., the n
D
can be determined). Figure 6.4 illustrates this behaviour
with an intermittent measurement signal. When the signal drop is shorter than
the tolerance time (e.g. at t = 10 s or t = 35 s in the figure), the output signal does
not drop. If the signal drop is so long that the tolerance time counter reaches zero,
there will be a drop in the output signal (at t = 80 s in the figure)
CONC [%]
Signal with tolerance
Original signal
Filtered (damped) output
0 10 20 30 40 50 60 70 80 90 100
Time [s]
Tol. time counter
Figure 6.4 Effect of tolerance time on output
6.2.4 QF threshold
The QF threshold setting can be used to prevent the instrument from measuring
when the image quality is below a certain limiting value. When QF value becomes
less than the user defined value the image status changes to NO OPTICAL IMAGE
after the user defined tolerance time (see Section 6.2.3 for tolerance time). By
default the QF threshold value is -1000.
6.2.5 Hold source interactions
There are three different reasons why the measurement signal may be in hold. All
three result in the same behaviour, but they also interact with each other.
Wash-related hold (Section 6.2.2) and external hold (Section 6.2.1) are connected
in parallel. If at least one of them is active, the measurement result will be in hold.
Tolerance time (Section 6.2.3) is independent of these two, but the tolerance time
will be reset whenever there is another reason for the measurement hold.