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170
Reference Manual
00809-0100-4840, Rev CB
Appendix F: Programming the 3102 and 3105 using HART
February 2015
Programming the 3102 and 3105 using HART
F.3.27
Lost echo delay (P021)
In pulse echo level measurement systems, ultrasonic pulse echoes are sometimes lost due to
adverse liquid surface conditions such as turbulence or foam. The ultrasonic pulse transmitted
towards the surface is sometimes not returned, deflected away from the transmitter, or
attenuated significantly. In these conditions, the transmitter holds the last valid data and
transmits another pulse to see if the echo is returned.
Lost Echo Delay (P021) defines the period that the transmitter will hold and display the present
valid surface measurement, waiting to update the measurement when the echo is recovered.
A “lost echo” fault condition is signalled if the Lost Echo Delay period ends with no valid echoes
returned.
A valid returned echo occurs inside a 'window' on either side of the liquid level. The 'window'
increases as the range to the target increases. All echoes within the ‘window’ are monitored and
averaged to smooth of the liquid level output under turbulent conditions.
Any returned echo from closer than the liquid surface is considered valid if a minimum required
number of echoes (
) have been received. The output will then change to this new
value.
Any echo returned further than the liquid surface and outside the 'window' is ignored. However,
if a lost echo condition is developing and a period (Lost Echo Delay divided by two
(1)
) has
elapsed, any echoes received from further away targets are treated as valid. The liquid level
measured changes to the new value after receiving four such echoes.
Field Communicator or AMS Device
Manager
To view or change the lost echo delay
1.
From the
Home
screen, select 2: Configure.
2.
Select 2: Manual Setup
3.
Select 5: Engineering (
3105
) or
6: Engineering (
3102
).
4.
Select 1: Lost Echo Delay P021.
5.
If a change is required:
(a) Input a new value, and then select “ENTER” to save it.
(b) Select “Send” or “Apply” to update the transmitter.
Note
When messages appear, take appropriate action if needed and select “OK”.
Fast Keys
2, 2, 5 [or 6], 1
(1)
Maximum of 20 seconds.
Lost Echo Delay P021
900 s
900
ESC
DEL
ENTER
HELP
w
s
q
a
z
Lock
Shift
@ &
á ü
x
e
d
c
r
f
v
t
g
b
y
h
n
u
j
m
*
-
+
/
.
0
7
4
1
8
5
2
9
6
3
i
k
o
l
FN
(
Field Communicator Screen Shown
)
Summary of Contents for Rosemount 3101
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Page 4: ...ii Reference Manual 00809 0100 4840 Rev CB Title Page February 2015 ...
Page 12: ...x Reference Manual 00809 0100 4840 Rev CB Contents February 2015 Contents ...
Page 34: ...22 Reference Manual 00809 0100 4840 Rev CB Section 3 Installation February 2015 Installation ...
Page 68: ...56 Reference Manual 00809 0100 4840 Rev CB Section 4 Starting up February 2015 Starting up ...
Page 236: ...224 Reference Manual 00809 0100 4840 Rev CB Index February 2015 Index ...
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