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Levelogger User Guide - Software Version 3.4.0 or Higher
Page 7
1.1 Level
The Levelogger Gold and Levelogger Junior use a high quality piezoresistive
silicon pressure transducer packaged in 316L stainless steel housing. It gives high
accuracy and high stability. The Levelogger Gold body is coated with Zirconium
Nitride (ZrN) to give corrosion resistance. All Leveloggers measure total or
absolute pressure. When the Levelogger is operating in open air, it is recording
barometric pressure and converting that pressure reading to its water level
equivalent above the datalogger’s pressure zero point of 950 cm (31.17ft). When
submerged, it is recording the combination of barometric pressure and water
pressure. The Levelogger converts the total pressure reading to its corresponding
water level equivalent. Actual water level is obtained by compensating for
barometric pressure. The best method to compensate for barometric pressure
is to employ a Barologger above the water level, somewhere on site, to obtain
records of barometric pressure. The Levelogger Software includes a Barometric
Compensation Wizard, which guides the user through the automated process of
barometric compensation. Manual methods can be employed to determine the
absolute water level using barometric records collected on-site or available from
a local weather station (i.e. Airport). Water level readings from the Levelogger
Gold and Levelogger Junior models are temperature-compensated.
1.1.1 Pressure Calibration
The Levelogger Gold and Levelogger Junior are calibrated against a range of set
reference points to an accuracy of 3 decimal places. The units of pressure are
in pounds per square inch. The conversion factor for pounds per square inch
relates to pressure as follows:
1 pound per square inch = 0.0689476 bar
= 0.703070 m
= 703.070 kg/m
2
= 6.895 kPa
= 2.31 ft. H
2
0 @ 4°C.
During the calibration procedure, the Levelogger is fully submerged in a highly
accurate water bath. The bath is set to 15°C and allowed to stabilize. The
pressure is then calibrated to six separate pressure points covering the entire
range of pressure for that particular Levelogger to check for any non-linearity.
The process is repeated again at 35°C to check for temperature effects. Once
done, the Levelogger is approved after all specifications for accuracy, precision,
stability and hysteresis have been met. The Levelogger should be calibrated for
the life-time of the instrument, as long as it is used within its specified range.
1.2 Barologger
The Barologger Gold is designed for use in air only. It has a specific range and
firmware algorithms based on air pressure rather than water pressure. This
makes the Barologger less accurate if used in water, but more accurate if used as
intended, in air. Using a Barologger is the most accurate and convenient method
of obtaining atmospheric pressure and air temperature. When programmed
with the same sampling parameters as the Leveloggers on site, a Barologger
can avoid barometric data time lags and any errors introduced due to moisture
buildup, kinking or damage to vented cable. The Barometric Compensation
Wizard in the Levelogger Software simplifies the adjustment of the level
measurements for barometric pressure changes, by using the synchronized data
from all Leveloggers on site and the site Barologger.