The CTD versions of the DCX-22 range are autonomous battery-operated data collectors made of stainless steel. CTD stands for Conductivity, Temperature and Depth. Requiring little maintenance, they record the water level (pressure), temperature and conductivity over long periods.
Conductivity is increasingly being monitored in conjunction with depth measurements, in which changes in water quality and depth are required to be detected simultaneously. Thus it is possible to detect contamination caused by salt water infiltration, waterborne particles or general pollutants when measuring groundwater levels.
KELLER's Logger 5.1 programming and readout software is used to select a conductivity range (0…0.2 mS/cm, 0…2 mS/cm, 0…20 mS/cm or 0…200 mS/cm) and set the temperature coefficient for the medium. This process produces compensated conductivity measured values standardized at 25 °C.
DCX-22 AA CTD
The DCX-22 AA CTD data collector records water levels using the AA (absolute-absolute) measurement method, whereby fluctuations in atmospheric pressure are measured and compensated for by the watertight atmospheric pressure sensor with its stainless steel diaphragm. The advantage of this measurement method is that no humidity-sensitive capillary tube is required. Additionally, it is not required that the DCX-22 AA CTD be removed from the immersion tube in order to extract the data.
In the DCX-22 CTD, the sensor, electronics and battery are contained within the same housing. The data collector needs to be withdrawn from the immersion tube in order to extract the data. The DCX-22 CTD uses an absolute pressure sensor. In shallow water, where the impact of atmospheric pressure fluctuations also needs to be taken into account, a second DCX, acting as a barometer, is placed at the surface to record changes in atmospheric pressure. The pressure difference or, as appropriate, the water level is then calculated in the PC by subtracting both measured values.
DCX-22 SG/VG CTD
The DCX-22 SG/VG CTD versions have a cable outlet, negating the need to withdraw the instrument from the immersion tube in order to read out the data. A locking disc is used to secure the interface connector at the surface. In the VG version (reference pressure measurement), the reference equalization capillary tube in the cable is inserted into the upper housing (read-out connector), where the reference opening protected by a Gore-Tex® diaphragm is located.
|Measurement Range - Pressure||cf. Data Sheet
DCX-22 AA and DCX-22 (SG/VG)
|Measurement Range - Conductivity||0…200 mS/cm (milliSiemens per centimeter)|
|Accuracy - Pressure Sensor||± 0,02 %FS max.|
|Accuracy - Conductivity Sensor||± 1% max. of the selected range|
|Accuracy Temperature Sensor PT100||Accuracy 0,1 °C (-10…60 °C)|
Software for read-out and configuration of data loggers. The data can be processed i.e. graphical representation, exportation, compensation of ambient pressure as well as conversion into water level. The online function shows actual measurements of the device.