Xylem WL16 WATER LEVEL LOGGERS - Manual (Page 29)

Global Water
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XVII.
Adjusting the Zero Reference Level:
The sensor on the WL16 level logger measures the depth of water from the end of
the sensor to the surface. However, it is sometimes desirable to know the water
depth from a reference level other than the surface. For example: In a ground water
well, you may want to know the distance from the surface of the water to ground
level, not to the sensor.
The WL16 comes factory calibrated to measure depth from sensor to surface.
Setting the reference level to something other than the water surface is easily
accomplished by manually changing the Low EU and High EU numbers in the
Analog Setup menu. If done correctly, this does not change the calibration of the
sensor but rather, just changes the scale of the data to read in any desired range.
Just one rule must be followed: The difference between the High EU and Low
EU numbers bust be equal to the depth at which the sensor was calibrated.
For example: If you have a sensor with a range of 0-30 feet, the logger has been
factory calibrated at a range of 30 feet. The High and Low EU numbers can be
changed to read any range without changing the accuracy, as long as the difference
between them remains 30 feet. If you need to recalibrate the WL16 but do not have
a 30 foot depth of water available, you can recalibrate at 20 feet (or whatever is
available to you) as long as the difference between the High and Low EU numbers is
equal to the calibration depth (in this case, 20 feet).
If you wish to record the depth from sensor to water
surface, the Low EU number is always zero and the
High EU number is always equal to the depth at which
the sensor was calibrated. Selecting a reference level other
than the water surface is illustrated in the following examples.
Example 1:
Recording the distance from the top of the well pipe to water level:
Changing the zero reference to the top of the well pipe requires
that you know the distance from the top of the pipe to the end of
the sensor at the time of installation. Note that the cable length
provided with the WL16 is not exact and should not be used as a
standard without first measuring it. To change the High and Low EU
fields, and thus the recorded level, follow these steps: