Van Essen CTD-Diver DI28 Series, Руководство по эксплуатации продукта

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4
The CTD-Diver measures a pressure of 1,170 cmH
2
O and the Baro-Diver measures a pressure
of 1,030 cmH
2
O. Substituting these values into equation (1), results in a water column of 140
cm above the Diver: WC = 140 cm.
Substituting the values of the manual measurement and the water column in equation (4)
results in the following cable length: CL = 120 + 140 = 260 cm.
The water level in relation to MSL can now be easily calculated using equation (2): WL = 150
260 + 140 = 30 cm above MSL.
Measuring Temperature
All Divers measure the groundwater temperature. This can, for example, provide information about
groundwater flows.
The temperature is measured using a semiconductor sensor. This sensor not only measures the
temperature, but also uses the value of the temperature at the same time to compensate the pressure
sensor and electronics for the effects of temperature to ensure the best possible performance.
Measuring Conductivity
In addition to water levels and temperature, the CTD-
conductivity in milli Siemens per centimeter (mS/cm). A change in conductivity may be caused by for
example changes in water flow or increasing/decreasing pollution or salinization.
The conductivity is measured using a 4-electrode measuring cell. This type of measuring cell is
relatively insensitive to sensor fouling, thus keeping maintenance to a minimum.
The measuring cell
combined with the selected measurement method results in an electrolysis-free measurement system.
The CTD-Diver measures the conductivity of a solution. The CTD-Diver can be programmed to
measure either the true conductivity or the specific conductivity. The specific conductivity is defined
as the conductivity as if the temperature is 25 °C. This setting must be programmed prior to starting
the CTD-Diver.
The conductivity of a liquid depends on the type of ions in the liquid and to a significant degree on the
This dependency is indicated on the packaging of the calibration solution. The
diagram below displays the conductivity as a function of temperature for three different calibration
liquids. The specified value of the calibration liquid is the conductivity of the liquid at 25
 C.