Levelogger Series User Guide
Page 17
1.2.3 Temperature
Leveloggers record temperature compensated water levels. Groundwater and surface water temperature
measurements are particularly important in situations where temperatures may fluctuate significantly, and
where its accuracy is important in determining liquid level, viscosity and hydraulic conductivity. Temperature
monitoring is vital in the calculation of certain temperature dependent contaminant reaction rates. A Platinum
Resistance Temperature Detector is used to accurately compensate for temperature changes within the range
of 0 to +50ºC for the Levelogger 5 and Levelogger 5 LTC, -10ºC to +50ºC for the Barologger 5, and
0 to +40ºC for the Levelogger 5 Junior. The Levelogger will record temperature in its thermal range of
-20 to +80ºC, but outside the range, compensation will be less accurate.
1.2.4 Conductivity
The Levelogger LTC models provide the added feature of electrical conductivity measurement; they measure
the actual conductivity at the current temperature. Conductivity measurement is particularly useful in
monitoring saltwater intrusion, surface water infiltration and mixing, as well as being an indicator of certain
pollutants and contaminant parameters. Conductivity is measured via a platinum 4-electrode sensor, which
produces highly stable and consistent readings. Conductivity calibration is performed by using up to 4 specific
calibration solution ranges, and the Calibration Wizard in the Levelogger Windows Software.
The Data Wizard allows you to convert conductivity readings to Specific Conductance (at 25ºC), Salinity
expressed in Practical Salinity Units (PSU), or TDS. A Practical Salinity Unit (PSU) is a dimensionless descriptor
for the Practical Salinity Scale (PSS). The PSS defines salinity as the ratio of a water sample's conductivity
to that of a standard KCL solution. The Data Wizard uses the equation given in the UNESCO Technical
Paper "Algorithms for computation of fundamental properties of seawater", to convert Conductivity readings
to Salinity. For more information, see: Fofonoff, N. P. and R.C. Millard, Jr. Algorithms for computation
of fundamental properties of seawater, UNESCO, Tech. Pap. Mar. Sci.,44. The Data Wizard uses the
known equation “TDS=keEC” to convert Conductivity readings to TDS, where TDS is expressed in mg/L
or ppm and EC is the electrical conductivity in µS/cm at 25˚C. Correlation factor ke is between 0.55 -
0.8. For more information, see: Al Dahaan, S.A.M., Al-Ansari, N. and Knutsson, S. (2016) Influence of
Groundwater Hypothetical Salts on Electrical Conductivity Total Dissolved Solids. Engineering, 8, 823-830.
http://dx.doi.org/10.4236/eng.2016.811074
Note: For every degree change in temperature, there is approximately a 2% change in conductivity. To convert raw
conductivity measurements to Specific Conductance measurements, you can use the following equation:
Specific Conductance = Conductivity / (1 + 0.02 * (temp(C) - 25))
You can also perform this calculation automatically using the Data Wizard.
1.2.4.1 Calibration of the Conductivity Sensor
The conductivity sensor of a LTC Levelogger is a highly sensitive device requiring regular calibration by the
user. The conductivity calibration frequency is dependent on the water quality of the Levelogger’s monitoring
environment. To determine whether a LTC Levelogger should be re-calibrated, test the unit in a solution
with a known electrical conductivity value at a reference temperature. In Real Time View, observe current
readings by using the Read Now function. If this reading varies from the known Specific Conductance of the
solution by greater than the stated accuracy of the conductivity measurement, the unit should be re-calibrated
using the Conductivity Calibration Wizard procedure outlined in Section 6. As a minimum, calibrate your
LTC Levelogger at least twice a year. Ensure that a conductivity calibration is performed when the
LTC Levelogger is being set up for its initial use and after long periods of dry storage.
1.2.5 Total Rainfall
Solinst Rainloggers are designed to record the number of tips of an external tipping-bucket rain gauge, and
output the amount of rainfall per tip.
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