Grant Instruments
30641 V1.3
Yoyolog
Page 28
Operating Manual
7.5.13 Soil moisture sensor - Decagon series (YL-M90 only)
The ECH2O probes can be connected to the
YL-M90
for measuring soil moisture.
The sensors of the ECH2O series are capacitive sensors for soil moisture that
measure the permittivity of soil. An output signal proportional to the soil moisture is
created by altering the sensor’s reference voltage. The significant differences between
the permittivity of water (ca. 80), soil (ca. 4) and air (ca. 1) are beneficial in the
measuring principle as the changes in moisture content, result in a large change in the
permittivity of the soil.
The influences of the soil’s temperature and salinity are minimized by the specialist
surface coating of the sensor.
Specifications:
EC-5
Measuring range: 0-saturation
Accuracy: <0,03m³/m³ for all soils, up to 8 dS/m
With soil specific calibration: +/-0,02 ³/m³ (+/-2%)
Resolution: 0,001 m³/m³ VWC in mineral soils. 0,25% in natural soil
Operating temperature range: -40-60°C
Selecting the measuring site
When selecting the site to measure be aware that the immediate surrounding area of
the sensor has the most influence on the readings.
For example, holes, cavities, and compactions can have an effect on the
measurements.
Do not install the sensor near large metal objects as this can affect the magnetic field
surrounding the sensor.
Please be aware of objects (such as sticks and stones) between the sensor brackets
as these may affect the measurements.
When installing the sensor please make sure that the contact areas between the
sensor and the soil are maximised.
Two methods can be helpful in siting the sensor:
