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51-638 Echotel Model 338 Two-Wire Ultrasonic Transmitter
P29
False target
Factory default value for P29 is: 0.0
A fixed object in the tank can be blocked out if it is within
the ultrasonic beam angle and is creating a false echo.
Measure the distance of the object from the face of the
transducer and enter this into P29.
NOTE:
P30
is not used by the Model 338 transmitter. Default value is 00.
P31
Speed of sound through gas
Factory default value for P31 is: 1,128 ft/sec
(US units) or 343.8 m/sec (metric units)
NOTE: The default value should not be changed unless instructed to
do so by the factory. Changing the default value of P31 will
alter all measurements made by the Model 338.
Parameter P31 can be used if ultrasonic signal will be trav-
eling through a vapor other than air. The default value of
1,128 ft/sec (343.8 m/sec) assumes that the ultrasonic sig-
nal will be traveling through air. Since the speed of sound
is different in gases other than air, P31 allows an adjust-
ment to be made for this difference. This parameter should
only be used if the gas is homogenous throughout the
tank. It should not be used if there are stratified layers of
a gas in the tank. Refer to
Section 2.5, Velocity of Sound In
Gases Other Than Air,
enter the new speed of sound in P31.
P32
Specific gravity
Factory default value for P32 is: 0.00
Entering a value other than the default of 0.00, will allow
the 338 to display the weight of the material in the tank.
Prior to displaying weight, the 338 must be configured for
volume by following these steps:
1.
Set the measurement mode for volume in P01.
2.
Select the weight units in P02.
3.
Configure the tank shape by entering values in
P40 – P45.
4.
Enter the density (specific gravity) value in P32.
After completing the above four steps, return to the meas-
urement mode. The LCD will indicate VOL, but there
will not be pointer at the ft3/m3 section of the LCD.
Depending on the value entered in P02, the unit will dis-
play weight in either tons or pounds. When displaying
tons, the LCD will have a triangle pointing to the "t" in
the lower left side of the display. When displaying pounds,
this pointer does not appear.
