Decagon 5TM Sensor

– soil moisture & temperature sensor

Soil Moisture Temperature Probe


The 5TM delivers temperature, measured by an onboard thermistor, along with accurate volumetric water content.


The 5TM determines volumetric water content (VWC) by measuring the dielectric constant of the soil (or other media) using capacitance/frequency domain technology. Signal filtering minimizes salinity and textural effects, making the 5TM accurate in most soils and soilless media. Factory calibrations are included for mineral soils, potting soils, rockwool, and perlite.


easy installation

The 5TM’s small size makes it easy to install in the field and the greenhouse. This robust sensor can be pushed directly into undisturbed soil to ensure good accuracy.


Soil Moisture Temperature Sensor


plug and read

Get straight to the data with an Em50-series data logger. Just install the 5TM, plug it into the Em50, set the clock and measurement intervals, and start logging data. No programming required.

Em50 Data LoggerThe 5TM comes standard with both serial and SDI-12 communication options, meaning easy integration with systems manufactured by other companies.


advantages of the 5TM
  • Measures VWC and temperature
  • SDI-12 compatible
  • 715 mL volume of influence


related products


feature specification
Soil Moisture Apparent Dielectric Permittivity (εa): ± 1 εa from 1 - 40 (soil range); ± 15% from 40 - 80 Soil Volumetric Water Content (VWC): Using Topp equation: ± 0.03 m3/m3 (± 3% VWC) typical in mineral soils that have solution electircal conductivity < 10 dS/m; using medium specific calibration, ± 0.02 m3/m3 (± 2% VWC) in any porous medium
Temperature Temperature: ± 1°C Note: Temperature measurement may not be accurate if sensor is not fully immersed in the medium of interest, due to excessively long equilibration time.
Soil Moisture εa: 0.1 εa from 1-20, < 0.75 εa from 20-80 VWC: 0.0008 m3/m3 (0.08% VWC) from 0 to 50% VWC
Temperature 0.1°C
Soil Moisture εa: 1 (air) to 80 (water) VWC: 0% to saturation
Temperature -40 to 60°C
sensor type
Soil Moisture Frequency domain / capacitance
Temperature Thermistor
Measurement Speed 150 ms (milliseconds)
Output SDI-12
Operating Environment -40°C to 60°C
Power Requirements 3.6 - 15 VDC, 0.3 mA quiescent, 10 mA during 150 ms measurement
Cable Length Sensors come standard with 5 m cable. Custom cable lengths available. Maximum cable length of 75 m.
Cable Connectors 3.5 mm "stereo" plug, or stripped and tinned lead wires (3)
Sensor Size 10 cm x 3.2 cm x 0.7cm
Data Logger Compatibility Decagon Em50 Series, ProCheck, SDI-12 data loggers
Warranty One year, parts and labor



further information