Delta-T Devices Ltd.

- Model SM150T - Soil Moisture and Temperature Sensor


Dependable ± 3% soil moisture accuracy - Built in temperature measurement - Robust and buriable, with 5 year warranty. The SM150T measures soil moisture and temperature with research-grade accuracy. It offers stable, robust and reliable performance at a great price. The SM150T’s advanced patented electronics and tough build produce a highly dependable sensor with exceptional salinity and temperature stability. The SM150T is engineered to withstand long term burial - the sensor, connectors and cable are all environmentally protected to IP68. It offers moisture accuracy of ± 3% (after soil specific calibration) and the built in temperature sensor achieves ± 0.5°C. The SM150T is a dual purpose probe - it can be used portably for instant moisture readings, or left installed in the soil connected to a data logger, to provide long-term moisture and temperature data.

The SM150T can be logged by any Delta-T Devices data logger and by many loggers from other manufacturers (simple 0-1 V output for moisture, 10K thermistor for temperature). To record temperature the sensor must be fully buried and connected to a data logger.

The SM150T is available as part of the convenient SM150 Kit, complete with carry case and HH150 readout meter.  Find out more about the SM150 Kit.

Please note that the HH150 Meter supplied with the SM150 Kit is a readout-only device. If PC connectivity for data storage and download is a requirement, the SM150T should be used with the HH2 Moisture Meter instead.

NB: When used in portable mode the SM150T Sensor does not provide temperature indication.

The SM150T is easy to insert and install – its sharp pins minimise soil disturbance and preserve the original soil structure around the measurement rods. For burial at depth the cylindrical shape facilitates installation in augered holes. The threaded base of the sensor can be connected to optional 50cm and 100cm extension tubes, which assist with placement and removal.

The SM150T uses the same high quality range of cables and extensions as the ML3 and EQ3 sensors.

The SM150T comes complete with general calibrations for mineral and organic soils. A two-point soil specific calibration can be performed for greater accuracy if required.

Soil science – The SM150T is easy to install and provides accurate measurement of soil moisture and temperature – simplifying the vertical profiling of both parameters. (Temperature measurement requires burial of the probe).

Horticulture – With a length of only 143 mm (rods 51 mm), the SM150T can be installed in grow-bags and plant pots. For portable use, the SM150 Kit provides a simple, rugged solution to checking the uniformity of growing conditions across many types of growing media. Substrate calibrations include perlite, coir, peat, and mineral wool, as well as soils. SM150T for Horticulture use.

Irrigation – The accuracy and ruggedness of the SM150T makes it a natural choice for system integrators.

Product history

The SM150T replaces both the SM300 and SM150 Sensors, combining their strengths and offering great value.

  • Measurement: Volumetric water content and soil temperature
  • Accuracy: ± 0.03 m3.m-3 (3%) With soil-specific calibration
    • ± 0.5°C (0 to 40°C for temp sensor)
    • ± 0.75°C (-20 to +60°C for temp sensor)
  • Soil moisture measurement range:
    • Full accuracy over: 0 to 0.7 m3.m-3
    • Full range : 0 to 1.0 m3.m-3
  • Salinity range:
    • 50 to 500 mS.m-1
    • Salinity errors < 0.035 m3.m-3 from 0.05 to 0.4 m3.m-3. Can be calibrated up to 2000 mS.m-1
  • Temperature range: Full accuracy over: 0 to 40°C
    • Output: 0 to 1.0 V differential
    • Corresponding to 0 to ~0.6 m3.m-3
    • Resistance 5.8Ω to 28Ω for temp sensor
  • Power requirement: 5-14 V, ~18 mA for 1s
  • Minimum 5 V with 100 m cable
  • Environmental: IP68 (-40 to +70°C)
  • Sample volume:
    • ~55 x 70 mm diameter
    • Sample volume is weighted towards soil immediately surrounding the rods
  • Dimensions and weight:
    • Overall: 143 x 40 mm diameter
    • Rods: 51 mm x 2.5 mm diameter
    • Weight: 0.1 kg (exc. cable)
  • Sensor calibrations:
    • Individual sensors are interchangeable
    • Recalibration advised every 3 years (depending on use)
  • Soil calibrations: Generalised Mineral and Organic soil calibrations are supplied