data logger.

A specific version is the diver.

Pressure in cm H ₂ O.

temperature in ⁰ C.

EC in mS/cm (depending on type).

• homogeneous well-permeable sand package
• one sand package, with poorly permeable layers
• poorly permeable top layer, cross-section with layers of sand
  
  
   

The data logger is suspended in a monitoring well. Measurements are taken at a preset time interval and stored in the memory of the data logger. At the end of the period, all data is read out with a computer.

The following techniques are available for reading the data logger without first removing it from the monitoring well:

• Data cable: with this cable the data logger can be connected to a computer at ground level near the monitoring well for reading and programming;
• Diver-NETZ (specific for datalogger type Divers): the datalogger is connected by means of a DDC to a transmitter, with which the data from the datalogger can be sent wirelessly to a PDA or laptop. Monitoring wells can also be networked in this way. The distance range of the transmitter is approximately 100 – 150 m.
• Telemetry: The data logger is connected to a field modem by means of a cable. Messages are sent from the field modem with the measurement data. The messages can be received at any location. This means that it is no longer necessary to read out the data logger in the field.
• Reading the data logger with bluetooth.

The data logger is a pressure transducer in which some versions can also measure parameters such as temperature, EC or oxygen content. After programming, the data logger is suspended in a monitoring well. To derive groundwater levels, the use of a so-called 'baro-logger' is necessary. The baro-logger measures the air pressure. With the data from the baro-logger, the measurements of the ordinary data loggers are corrected for air pressure variations (the ordinary data logger measures the air pressure + the pressure of the water column above the data logger). Some data loggers have built-in baro loggers.

After a certain period (depending on the nature and purpose of the assignment and the selected measurement frequency), the data is read from the data logger.

A data logger can also be used to perform surface water level measurements.

A data logger can be hung in a monitoring well for a longer period of time (eg monthly, quarterly or half yearly). The data logger can be programmed with which time interval measurements should be performed and stored.

Setting and reading a data logger can take place within 1 hour. Measurement frequency can be preset (between 0.5 sec and 99 hours).

- Standard data logger: approximately €500

- Baro logger: approximately € 350

- Cost of field investigation (including placing monitoring well, driving costs and installing data logger)

Various projects where groundwater levels/quality must be recorded for a longer period of time or with a relatively high measuring frequency, such as:

• monitoring;
• permeability measurements / pump tests;
• monitoring the effects of water system interventions (groundwater abstraction / water level change);
• determine the response of the groundwater system to precipitation events.

Before installing and retrieving a data logger, perform a manual measurement of the groundwater level.

Measure the height at the top of the monitoring well in relation to NAP.

Measuring and registering the depth at which the data logger hangs.

Water pressure correction for air pressure variances.

Hang data logger too shallow (data logger falls dry)

Hang data logger too deep (note measuring range!)