Revision 8 SLG 700 SmartLine Level Transmitter User’s Manual Page 35
It is possible for the level to rapidly leave a blocking zone and exceed the maximum fill rate. Note
that the 'maximum fill rate' is the user-set maximum rate at which the level can change which will be
reported before a digital flag will be set. As discussed in 2.3.3, when the maximum fill rate is
exceeded, the transmitter considers the level lost and the gauge initiates the echo lost timeout counter
and sets the digital 'rate of change exceeded' flag. Software R200 differs from previous versions as to
the subsequent sensor behavior. In R200 and higher, depending on the latching mode settings, the
gauge will eventually initiate a new full probe scan and likely recover the level. Prior to R200, the
sensor would remain in the blocking zone until reset.
The maximum value for maximum fill rate is 0.9 m/s. 0.9 m is also close to the maximum amount
that the transmitter can detect a level change between two readings. If this value is exceeded the 'rate
of change' flag will not be set.
If the maximum filling rate is exceeded, the transmitter will continue to search for it in a narrow
region for it until the echo-lost timeout is expired. The transmitter will then enter a measurement fault
condition and search for the level over the entire probe length.
Note that if the rate of change is greater than a value greater than 0.9 m/s, the transmitter will likely
not track the level and only a level lost fault condition is set, without the ROC alarm. may not be able
to set a rate of change alarm. If the measurement is outside the blocking zones the transmitter will
display a measurement fault until the echo lost timeout period has been exceeded, and then it will
search for the level again. If it starts in a blocking distance position, it will stay in the blocking
distance until the level reappears within the distance allowed by the ROC limit0.9 m of the blocking
zone. However, as of R200, if the level appears suddenly outside of blocking distance, failing ROC a
level lost fault condition is set and output is maintained at the value of the blocking zone. This change
has important consequences if latching mode is not set.
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