Technical reference
A.3 Near blanking
SITRANS Probe LR with mA/HART
Operating Instructions, 05/2019, A5E32337711-AC
87
Typical receiver signal
①
End of transmit
②
P800 Near blanking
③
Distance from process empty level to reference point P006
④
Empty level
⑤
Range extension (P801) as % P006
A.3
Near blanking
Near Blanking
1)
programs SITRANS Probe LR to ignore the zone in front of the antenna. The
default blanking distance is 0.3 m (1 ft) plus any shield length, from the reference point
2)
.
P800 allows you to increase the near blanking value from its factory setting. But Auto False-
Echo Suppression (P837) is generally recommended in preference to extending the blanking
distance from factory values.
1)
Also referred to as "Blanking".
2)
For the reference point, see SITRANS Probe LR dimensions (Page 84).
A.4
Loss of echo (LOE)
A loss of echo (LOE) occurs when the calculated measurement is judged to be unreliable
because the confidence value (P805) is less than the threshold value (P804). If the LOE
condition persists beyond the time limit set by the Failsafe timer (P070), the Reliable Echo
indicator will be replaced by the Unreliable Echo indicator. The reading will alternate at two
second intervals with the letters LOE.
Reliable echo indicator
Unreliable echo indicator
P070 determines the time to elapse after the last valid reading before a Failsafe state is
activated. P071 determines the level to be reported when the Failsafe timer expires. Upon
receiving a reliable echo, the loss of echo condition is aborted, the Reliable Echo indicator
replaces the Unreliable Echo indicator, and the reading and mA output return to the current
level.