User's Manual

Page 46 IQ Radar 300 PL-611
Operation
Operation Operation
Operation
Loss of Echo (LOE)
A loss of echo occurs when the IQ 300 deems the calculated measurement unreliable,
i.e. the confidence (P805) is less than the threshold (P804). Refer to Operation
Troubleshooting on page 91
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:
to
The response to LOE is set by P072. It determines whether the reading and mA output
are immediately forced to the fail-safe default (P071). Upon receiving a reliable echo, the
loss of echo condition is aborted (icon returns to full), and the reading and mA output
return to the present level at the rate set by P072.
Blanking
Near blanking (P800) is set to ignore the zone in front of the antenna where false echoes
can appear as an echo during the receive cycle (often created by internal impediments
like a ladder rung). Usually indicated by an incorrect high level reading, false echoes can
be overcome by increasing the near blanking value from its factory setting.
Far-end blanking is a feature that ignores the zone below the zero or empty level where
false echoes can appear at levels that interfere with the processing of the true echo.
Typical Receiver Signal
In applications where the zero level is above the bottom of the vessel and you need to
monitor the zone below the normal zero, range extension (P801) can extend the range
into far-end blanking. Range extension is entered as a percentage of P006. As range
extension reduces the protection afforded by the far-end blanking, it should be used
judiciously because excessive range extension can reduce measurement reliability and
accuracy. Range extension is factory set for 5% of P006. If false echoes appear after the
blanking zone, P801 should be increased accordingly.
0
level
end o
f
transmit
far-end blanking
range extension
(P801) as % P006
empty distance to antenna
P006
P800
near blanking
range