METER TEROS 10 - Apparent Dielectric Permittivity; Troubleshooting

15
TEROS 10
learn about METER calibration service (calibrations performed for a standard fee), review
the article on soil sensor calibration (metergroup.com/soil-sensor-calibration) or contact
Customer Support.
The calibration for several potting soils, perlite, and peat moss is shown in Equation 3:
Equation 3
Θ m
3
/ m
3
( )
= 2.137×10
−10
× RAW
3
−1.465×10
−6
× RAW
2
+ 3.566×10
−3
× RAW − 2.683
where RAW is the output from the METER data logger.
If using a non-METER data logger, VWC is given by Equation 4:
Equation 4
Θ m
3
/ m
3
( )
= 5.439×10
−10
×mV
3
− 2.731×10
−6
×mV
2
+ 4.868×10
−3
×mV − 2.683
4.1.3 APPARENT 
Apparent dielectric permittivity (e
a
) can be used to determine VWC using external published
equations such as the Topp equation (Topp et al. 1980). Dielectric permittivity is given by
Equation 5:
Equation 5
ε = 1.054×10
−4
×e
2.071×10
−3
×RAW
where RAW is the output from the METER data logger.
If using a non-METER data logger, VWC is given by Equation 6:
Equation 6
ε = 1.054×10
−1
×e
2.827×10
−3
×mV
4.2 TROUBLESHOOTING
Table 3 
Problem Possible Solution
Sensor not responding
Check power to the sensor.
Check sensor cable and 3.5-mm stereo plug connector integrity.
Check data logger wiring to ensure brown is power supply, orange is
analog out, and bare is ground.
Try plugging into a different logger port.
Sensor reading too low

Check for air gaps around sensor needles. These could be produced
below the surface of the substrate when the needle contacts a
large piece of material and pushes it out of the way, or if the sensor
is not inserted perfectly linearly.
Ensure the calibration equation being used is appropriate for the
media type. There are signicant differences between substrate
calibrations, so be sure to use the one specic to the substrate.
NOTE: Sensor will read slightly negative in air when functioning properly.