Page 22 SLG 700 SmartLine Level Transmitter User’s Manual Revision 8
The most recently updated background is also stored in permanent memory and is applied
after a sensor reset if dynamic background is enabled. At all times the sensor maintains a
copy of the original user-acquired (static) background echo and will revert to this if the
dynamic background feature is once again disabled. Re-enabling dynamic background at
that point starts the process anew. It is recommended that this feature is turned on in all
installations where build-up or ambient temperature swings over approximately 30°C (55°F)
are expected.
Accuracy and measurement range specifications
The available probe lengths for each probe type are summarized in Error! Reference source
not found.
'These accuracy specifications are defined under reference conditions, at other ambient
temperatures the accuracy specifications are increased by ±0.2 mm/°C or ±15 ppm/°C
whichever is greater.
The measurement accuracy over the probe length is the larger of ±3mm or ±0.03% of probe
length. At the top and bottom of the probe the measurement performance can deviate from
the ±3mm or ±0.03% accuracy specification.
The zones at the top and the bottom of the probe at which the accuracy deviates from the
accuracy spec is called upper and lower transition zones respectively.
As the level rises or falls in the upper and lower transition zone a point may be reach were the
transmitter cannot provide a level reading or the accuracy is worse than ±30mm, at this point
we have reach the minimum blocking distance that can be set in the transmitter.
Figure 2-7 to Figure 2-6 summarize the accuracy as a function of length for the available
probe types in addition Table 3-4 provides a tabular summary of the minimum blocking
distances and the transition zones. To meet the accuracy specifications near the end of the
probe (lower transition zone and minimum blocking distance low), the correct probe type and
probe length need to be configured.
Note that for a wire probe with an end weight or with a looped end the minimum blocking
distance low is measured from the top of the weight or the top of the loop’s crimp.
When the transmitter is installed in a nozzle then the distances are measured from the bottom
on the nozzle, i.e. where the nozzle transitions to the tank. In addition, when using a nozzle
the guidance provided in Section 3.2.9.2 needs to be followed.
For the following four figures in this section, T
up
and T
low
are upper and lower transition
zones respectively.
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