Accepted Papers - 3.pdf - UNESCO

incorporated in a single probe.
The probe is provided with a hermetically
sealed casing for protection against moisture. The
casing also serves as a Faraday cage to make the
probe insensitive to external electrical disturbances.
It is installed in a monitoring well by suspending it
by a steel wire. The probe automatically measures
and registers the level, temperature and conductivity
of water and stores readings in the internal memory
of the data logger. As current drain is very low, the
built-in battery has a lifespan of 8 to 10 years.
Technical specifications of a typical probe [ 2 ] are
given in Table 1. Fig. 2 depicts a typical electronic
probe and Fig. 3 its field installation.
Advantages of Electronic Probes
The electronic probes have the following
advantages:
• Small diameter, the probes can be installed in
small boreholes.
• Hermetically sealed casing for protection
against moisture and
external electrical disturbances.
• Accurate measurements for level, temperature
and conductivity
TABLE 1 : Technical Specifications
380
• Internal battery life 8 - 10 years.
• Dynamic compensation for ambient
temperature and barometric
pressure changes.
• Logging function programmed by a software,
readings downloadable
to a computer.
References
[1] Global Water Instrumentation (2005). WL-16
Water level logger. Global Water Instrumentation
Inc., Gold River, California, USA <
www.globalw.com >
[2] Eijkelkamp (2006). Divers – minidiver,
microdiver, ceradiver and CTD diver, Product
Specification Sheet, Eijkelkamp Agrisearch
Equipment, Giesbeek, Netherlands.
< www.eijelkamp.com >
Note : Photographs of the probes from websites /
product literature. Disclaimer: No preference to any
particular firm by the author.
With Table 1, Fig. 1 (a) – (d), Fig. 2, & Fig. 3.
Physical dimensions & weight :
18 to 22 mm (dia) x 90 to 183 mm (length), 55 to 150 gm (size and weight varies
with model). Pressure sensor, temperature sensor, conductivity sensor, data logger
and battery are encapsulated in a hermetically sealed stainless steel/ceramic housing.
Power supply :
Built-in battery (very low drain), typical life 8 - 10 years.
Measuring ranges & accuracies :
Water-level (depth) : 10 / 30 / 100 meters, +/- 0.1% of full scale.
Temperature : minus 20 to plus 80 deg C, +/- 0.1 deg C.
Conductivity : upto 80 mS/cm, +/- 1% of measured value.
Data logging :
16,000 to 48,000 measurements, at measurement frequency of 0.5 sec to 99 hours
(software programmed).