Umwelt-Geräte-Technik GmbH
| Eberswalder Str. 58 | D-15374 Müncheberg | Tel.: +49 (0) 33 43 2 - 89 575 |
The
ε
value can also be called up when making independent water content calculations
using other models.
4.2.
Electrical conductivity measurement
The UMP-1 sensor records the electrical conductivity of the soil by means of an
additional circuit (IC) independently of the soil moisture measurement. This system
offers two great advantages. On the one hand an extremely precise measurement of
conductivity is possible using the components and measurement principle. On the other
hand the independently measured conductivity can be used to correct the calculated
water content.
Small electrical conductivity values have no effect on the measurement of the dielectric
constant. However the effect on the dielectric constant becomes greater with increased
conductivity. Without correction the dielectric constant obtained is too high, so
producing a water content that is too high.
To measure conductivity, the soil moisture measurement is interrupted for a sort time,
and a signal in the kHz range transmitted over the antennae. The corresponding IC
measures the impedance of several different frequencies and averages the results.
4.3.
Temperature measurement
The UMP-1 sensor also measures the soil temperature using a further circuit. A stainless
steel bolt recessed between the probes transmits the temperature of the soil from the
point of water content and conductivity measurement to the temperature sensor, so
that all values originate from the same measurement point.
6 minutes should be allowed as setting time to achieve a reliable temperature
measurement.
5.
Installation
To conduct the measurement, the sensor is placed in the ground so that the probe rods and
the metal bolt for temperature measurement have a good contact to the soil. Air-filled
hollow spaces between soil and steel lead to distorted measurement results.
To simplify the installation and to protect the antennae, it is advisable to punch the
installation site with the supplied tool. The antennae of the punch are narrower than those
of the sensor which ensures good contact to the soil.
Caution!
The antennae must be completely in the ground because the measurement is always
along the entire antenna.
