38
Reference Manual
00809-0200-4840, Rev BA
December 2014
Section 4: Configuration
4.3.7
Upper blanking (P023)
This defines a zone close to the transmitter where echoes are to be ignored. Establishing this
zone eliminates echoes from false targets such as mounting fittings or the end of stub pipes.
Enter the vertical distance from the transmitter face to where a valid surface echo can be
detected. See
for this zone in a tank geometry illustration.
Note
In applications where elevated ambient temperatures of around 50 to 60 °C are
experienced, together with poor liquid surface conditions (excessive surface agitation,
foam, etc.) at a high level and within 0.5 m of the transducer face, the transmitter may
see a false echo and report a false high level measurement.
The factory default value of this parameter is 0.3 m, measured down from the
transducer face. If it is possible to operate with an increased value between 0.3 and 0.5
m, then setting P023 to a value of 0.5 m eliminates the false echo. Trying several
different values is recommended as a smaller value of
P023
, if the application requires,
may be possible. See also
Threshold 1 Size
(
) for related information.
The upper blanking distance should not be set to less than the factory default setting.
The pulse transmission stops if the sum of the
Lower Blanking
) and
Upper
Blanking
and is greater than the
Bottom Reference
).
Field Communicator or AMS
To view or change the upper blanking distance:
1.
From the
Home
screen, select
2: Configure
.
2.
Select
2: Manual Setup
.
3.
Select
5: Engineering
.
4.
Select
5: Upper Blanking P023
.
5.
Input the new upper blanking distance, and press “
ENTER
” to save it.
6.
Press “
SEND
” to update the transmitter.
Note
When messages appear, take appropriate action if needed and press “
OK
”.
Rosemount 3490 Series Control Unit
To view or change the upper blanking distance:
1.
From the
Main Menu
screen, select
SETUP
.
2.
Select the transmitter (e.g. “
Tx1: 3107
”).
3.
Select
ENGINEERING
.
Fast Keys
2, 2, 5, 5
Upper Blanking P023
1.000 ft
1.000 ft
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)
Upper Blanking P023
1.000ft
Esc=Quit =Edit
(Rosemount 3491 Screen)
Содержание 3107
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