17
51-638 Echotel Model 338 Two-Wire Ultrasonic Transmitter
P24: - - - a Target tracking speed
Factory default value for P24 is: 0.
P25: - - - a
Echo selection within the measurement
window
Factory default value for P25 is: 0.
Advanced digital signal processing within the 338 forms a
measurement "window" around the echo that is reflected
off the surface of the liquid. This measurement window
determines the distance that is used to calculate the level,
volume or open channel flow. A visual of this window is
shown at left as it would be seen on an oscilloscope.
Some applications may have multiple echoes that result
from false targets or noise within the vessel. Register P25
provides two different echo selection modes for the 338 to
use in forming the measurement window around the prop-
er signal.
Received
signal
amplitude
Echo 1
Echo 2
"t" ultrasound flight time
t
a
Tracking Speed
Application Conditions
0
Standard
For most applications
1
Fast
For fast changing level
2
Special
Used only in special applications. The meas-
uring window (see P25) becomes inactive,
and the 338 responds instantly to any target.
This can be used for extremely fast target
tracking, but is not recommended for level
applications.
Note: The maximum range is reduced in half
when this is used.
a
Echo Selected
Application
0
Echo with the highest
This default value is used for
amplitude
most Model 338 applications.
1
First Echo
For applications where false
targets may create multiple echoes
