The SMT100 is a world class soil moisture sensor with outstanding accuracy for demanding applications in science and precision agriculture. Researchers and farmers have trusted the sensor for over 10 years.

For unparalleled compatibility with data loggers and controllers the SMT100 is available with the following interfaces:

  • RS-485: TBUS/ASCII or Modbus

  • SDI-12

  • Analog voltage output: 0-10 V and customer specific voltage ranges like 0-1 V, 0-3 V or 0-5 V on request

  • 4-20 mA

  • Low voltage UART (especially for IoT radio modules)

Very accurate

High frequency precision measurement technique with outstanding resolution


Proven long term experience in harsh environments


Fully waterproof design with high quality materials

First slide
Fibre glass reinforced blade with embedded electrodes for moisture sensing
Epoxy potted electronic circuit with precision temperature sensor
Microbe resistant polyurethane cable for longest service life

SMT100 in research

Effective calibration of low-cost soil water content sensors

Analysis of a set of more than 700 SMT100 soil moisture sensors. Exceptional accuracy and minimal sensor-to-sensor variability was reported.


A soil moisture monitoring network...

Over 400 SMT100 soil moisture sensors with TRUEBNER dataloggers help scientist to better understand hydrological phenomena in karst systems.


A distributed soil moisture, temperature and...

65 SMT100 soil moisture sensors with specially designed water proof TRUEBNER dataloggers were installed underneath permeable pavements to study water and temperature fluxes in urban hydrology and climatology.



Soil volumetric water content (VWC):

Using factory calibration up to ± 3% (VWC) in mineral soils
with moderate salinity from 0 to 50% VWC
Using medium specific calibration up to ± 1% (VWC)


Typical ± 0.2°C, max. ± 0.4°C over full range (analog version ± 0.8°C)

Additional output (digital versions only):

Raw measurement data
Dielectric permittivity


0.1% volumetric water content or better
0.01°C or better (analog version 0.2°C)


0 to 60% volumetric water content (up to 100% volumetric water content with limited accuracy)
Temperature: -40 to +80°C (analog version -40 to +60°C)

Output options

RS-485 with TBUS
RS-485 with Modbus
RS-485 with ASCII
Analog: 0 - 10 V (other voltage ranges on request)
4-20 mA (only volumetric water content)
Low voltage UART (especially for IoT radio modules)


4-24 V DC, up to 40 mA during measurement (analog version 12 - 24 V DC for 0 - 10 V output)
Measurement time digital versions: less than 50 ms
Measurement time analog versions: less than 500 ms

Cable length


Sensor dimensions

18.2 cm x 3 cm x 1.2 cm

Data logger compatibility

Logger capable of appropriate power excitation and RS-485 (TBUS, Modbus, ASCII), SDI-12 or analog input
Free PC logger software available on request