4210 Flow Meter
Section 3 Installation
3-14
3.6.5 Suspension of the
Sensor
In addition, in stable, indoor environments, you can simply
suspend the ultrasonic level sensor from its cable. The previ-
ously-described Cable Straightener, which is weighted, and
which forces the ultrasonic level sensor to hang plumb, is
available to help in this mounting method.
3.6.6 Use a Level When you mount the ultrasonic level sensor, place it over the
center of the flow stream and use a circular bubble level to align
it vertically. This is very important, since misalignment may
result in erratic or erroneous level readings, resulting from the
echo bouncing off the walls of the channel.
3.6.7 Use the Variable
Blanking Feature
In step 1 of the program, select SETUP, then under setup, select
Measurement. Under MEASUREMENT, there is a menu called
VARIABLE BLANKING. If you select VARIABLE BLANKING,
the following will appear:
You can determine this distance approximately by measuring
from the face of the (installed) ultrasonic level sensor to the
surface of the channel just above the maximum expected liquid
level. This value tells the flow meter to ignore any echo reflected
from this distance or less.
The purpose of this selection is to let you fine-tune the reflection
cone beneath the ultrasonic level sensor. If the level sensor is
mounted too high above the flow stream, there is a good chance
echoes will be reflected from the channel walls, tops, sides, or
other solid surfaces, that have nothing to do with the actual
liquid level.
Proper selection of a value here will ensure that echoes selected
by the flow meter as valid will only come from the surface of the
flow stream, not the walls or sides of the channel.
3.6.8 Use the Signal Strength
Reading
In step 1, SETUP, there is a menu called STATUS. If you select
this menu, the flow meter will display the number, software
revision, etc. If you press Enter again, the following will appear:
This number indicates the strength of the ultrasonic return echo.
A number of 1 indicates a very weak return echo. A number of
100 indicates a very strong return echo; generally speaking, the
higher the number the better. Typical values will range from 10
to 90. You should adjust the ultrasonic level sensor for the
highest number here. If the flow meter and the level sensor are
installed a considerable distance from each other, you will need
an assistant to either watch the reading on the flow meter or
adjust the level sensor.
3.6.9 Minimizing Level
Measurement Errors
In order to minimize measurement errors with the 4210 Flow
Meter, the following precautions should be observed in the instal-
lation of the ultrasonic level sensor. These are listed in the
VARIABLE BLANKING
DISTANCE = XX.XX FT (or meters)
SIGNAL STRENGTH X%
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