7ML19981CJ01 MiniRanger Plus Page 35
Functional
In applications where the zero level is above the bottom of the vessel and it
is desired to monitor the zone below the normal zero, range extension
(P801) can be used to extend the range into the far end blanking. Range
extension is entered as a percent of P006. As range extension reduces the
protection afforded by the far end blanking, it should be used judiciously.
Avoid excessive range extension as this can reduce the measurement's
reliability and accuracy. Range extension is factory set for 20% of P006. If it
is found that false echoes are appearing ahead of the blanking zone, P006
should be reduced accordingly.
Blanking is automatically corrected for sound velocity change where
temperature and velocity compensation are used; keeping the blanking at
the distance at which it is set.
Loss of Echo
A loss of echo occurs when the MiniRanger Plus deems that the calculated
measurement is unreliable, i.e. the echo confidence (P805) is less than the
threshold (P804). This can be due to such circumstances as high level of
electrical noise, poor grounding or poor transducer aiming. Refer to
Troubleshooting. If the condition persists for a time beyond the limit as set by
the fail-safe timer (P070), the confidence icon changes from full to partial
and the reading and mA output are forced to the fail-save default (P071) at
the response rate (P003).
Upon receiving a reliable echo, the loss of echo condition is aborted (icon
returns to full) and the reading, mA and relay output return to the present
level at the response rate.
Relay operation responds, as programmed, to the default level as though an
actual material reading.
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