SMT100 Soil moisture and Soil Temperature Sensor

Through its special design and optimized measuring principle, the SMT100 combines the advantages of low-cost FDR sensors with the accuracy of TDR measurements. Where other soil moisture sensors reach their limits, the high operation frequency (> 100 MHz) as used in SMT 100 measurements allows allow this sensor to take reliable measurements even in dense clay soils. Further advantages include the short measuring time, a low sensitivity to salinity, and a large measuring range. Sensor and cable are maintenance-free, waterproof and frost-resistant. The SMT100 is therefore ideal for continuous operation.

The compact, functional and robust design of the glass-fiber reinforced, blade-shaped sensors enable simple installation for permanent measurements or easy insertion into the soil for manual point measurements with handset. Variants with different communication protocols (RS-485, SDI-12) as well as a version with analogue output are also available.

Advantages

• Accurate determination of soil water content
• Integrated temperature measurement
• Suitable for every soil type
• Easy installation (ongoing measurement) and insertion (manual measurement with handset) into soil
• Cost-effective
• Compatible with almost every logger system (interface options: Analogue Volt Signal, RS-485, SDI-12)

Technical Data

Sensor model name
Soil moisture and soil temperature sensor
Type SMT100


Scope of application
For continuous (permanent installation) or manual (insertion with handset) measurements of the volumetric water content of soil (SWC).


Suitable for
All soil types


Special features/limitations
Special feature: read out of additional information possible: »Raw data, dielectric permittivity
Limitation: Use for manual point measurements in highly abrasive technosols is not recommended


Measurement range
SWC:
0 to 60% volumetric water content (up to 100% volumetric water content with restricted accuracy)


Temperature:
Temperature: -40 to + 80 ° C (analogue version -40 to + 60 ° C)


Resolution
0.1% SWC
0.01 ° C (analogue version 0.2 ° C)


Accuracy

Volumetric water content (SWC)

• at factory calibration up to ± 3% (SWC) in mineral soil types with medium salinity of 0 to 50% VW
• for soil-specific calibration up to ± 1% (SWC)
  
  

Temperature
    typical ± 0.2 ° C, max. ± 0.4 °C over the entire measuring range (analogue version ± 0.8 °C)


Logger requirements and sensor output signal
All data loggers with suitable power supply and RS485
Interface (TBus, Modbus, ASCII), SDI-12 or
Analogue input 0 – 10 V (other voltage ranges on request)


Power supply
4 – 24 V DC, up to 40 mA peak during measurement
(Analogue version 12 – 24 V DC for 0 – 10 V output signal)
Measuring time digital versions: less than 50 ms
Measuring time analogue versions: less than 500 ms


Operational conditions
Air temperature: -25 to 70 ° C, rel. air humidity: 0 to 100%


Size & Weight (sensor without cable)
18.2 cm x 3 cm x 1.2 cm; about 80 g without cable


Sensor cable length
10 m, can be extended on request

Accessories & Compatible Products

Compatible sensors and peripherals:
From small and compact to an extensive measuring network, Ecomatik offers complete system solutions for sensor data acquisition in any desired size:

Maxi-Systems (e.g. Campbell data logger station)

Note

SMT soil moisture and soil temperature sensors are available in different output signal configurations. Availiable output options are analog DC, SDI-12 and RS485. They are therefore compatible with almost all common data loggers and microcontrollers with analog voltage input channels or digital SDI-12 or RS485 inputs. If you are unsure about the compatibility of an existing data logger, you are welcome to contact us at any time.