67
Reference Manual
00809-0200-4840, Rev BA
December 2014
Section 4: Configuration
4.3.27
Pulse repeat (P041)
The nominal rate of repetition for ultrasonic pulses from the transmitter is one pulse per second.
If two transmitters were located within the same tank, it is possible this would allow ultrasonic
pulses from one unit to be received by the other. If pulses were consistently occurring at the
same time, the receiving transmitter could mistakenly identify this crosstalk as a valid surface
echo. This can be prevented by having both transmitters operate with different rates of pulse
repetition, which means this interference is rejected as not consistent (pulse-to-pulse).
Pulse Repeat (P041) allows the pulse repetition interval to be adjusted by increments of 0.1
seconds in the range 0.5 to 2.0 seconds, allowing sufficient separation to avoid crosstalk
problems.
Field Communicator or AMS
This parameter is not available in the 3100 Series DD (Device Descriptor) file.
Rosemount 3490 Series Control Unit
To view or change the pulse rate:
1.
From the
Main Menu
screen, select
SETUP
.
2.
Select the transmitter (e.g. “
Tx1: 3107
”).
3.
Select
ENGINEERING
.
4.
Select
ADVANCED
.
5.
Select
Pulse Repeat
.
6.
Follow the on-screen instructions to edit and save the new setting.
(Press the
Enter
(
) key if prompted to change the mode to “off-line”).
7.
Select “
Quit
” to exit to the previous menu.
4.3.28
Echoes needed (P042)
Echoes Needed
is used to avoid stirrers that give occasional high level signals when they
protrude from the liquid surface.
The transmitter monitors the echoes returned from the liquid surface or any other target within
range. A valid surface echo is one that exceeds the signal strength threshold consistently for
more ultrasonic pulse cycles than set by Echoes Needed (P042).
The default value for Echoes Needed is four, meaning four echoes must be received
consecutively from a new surface echo before this is taken as the actual liquid level.
Fast Keys
–
Fast Keys
–
Pulse Repeat P041
Standard(1.0s)
Esc=Quit =Edit
(Rosemount 3491 Screen)
Содержание 3107
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