ML3 ThetaProbe by Delta-T Devices is a soil moisture and temperature sensor designed for accurate, reliable measurement in a range of soil types and conditions. Suitable for portable and buried use, it connects easily to data loggers and is made from stainless steel with replaceable rods. Delivers ±1% accuracy and operates in temperatures from -40°C to +70°C.

  • Soil moisture and temperature sensor for spot or continuous monitoring

  • ±1% soil moisture accuracy with soil-specific calibration

  • Can be buried or used as a portable probe

  • Easy connection to data loggers (0–1 V DC output)

  • Works in saline soils up to 2000 mS.m-1

  • IP68 environmental protection for long-term outdoor use

  • Replaceable stainless steel rods for extended product life

  • Includes thermistor for soil temperature measurement when fully buried

Applications

  • Irrigation management

  • Hydrology studies

  • Civil engineering projects

  • Soil water profiling

  • Pollution monitoring

  • Forestry research

  • Turf grass and sports field monitoring

Dimensions

Overall length: 158mm

Diameter: 40mm

Rod length: 60mm

Rod diameter: 3.2mm

Weight: 0.1kg (excluding cable)

Performance

Soil moisture accuracy: ±0.01 m3.m-3 (1%) with calibration

Temperature accuracy: ±0.5°C (0 to 40°C), ±0.75°C (-20 to +60°C)

Soil moisture measurement range: 0 to 1.0 m3.m-3

Salinity range: up to 2000 mS.m-1

Output: 0 to 1.0 V differential

Power requirement: 5–14 V DC, ~18 mA

Operating temperature: -40°C to +70°C (non-flexing cables)

Sample volume: approx 60 x 30mm diameter

Materials

Stainless steel rods

Installation

Fits augered holes 45mm diameter

Can be installed at depth using optional extension tubes (50 / 100cm)

Rods are replaceable if bent or damaged

Maintenance

Maintenance-free; recalibration advised periodically