Soil Moisture (20 cm probe) Smart Sensor

Part # S-SMA-M005
This product is discontinued.


Measure soil water content with the affordably-priced Soil Moisture Smart Sensor; this sensor integrates the field-proven ECH2O™ Sensor and a 12-bit A/D, providing ±4% accuracy in typical soil conditions, and ±2% accuracy with soil-specific calibration. The sensor’s thin profile and 20 cm probe length make the sensor easy to install, while measuring a representative cross-section of soil. Readings are provided directly in volumetric water content.

Highlighted Features

  • ±4% accuracy in typical soil conditions, and ±2% accuracy with soil-specific calibration.
  • 20 cm probe length
  • Compatible with Onset stand-alone and web-based weather stations

In what environment does this sensor operate?

This sensor operates in an outdoor environment.

What measurements does this sensor support?

The S-SMA-M005 sensor supports the following measurement: Soil Moisture

To see the full specifications for this product, please see our product manual found under the documentation tab if available.

Measurement Range:
In soil: 0 to 0.405(m³/m³)
Extended range: -0.29 to 1.4475 m³/m³ (full scale)
The sensor is capable of providing readings outside the standard volumetric water content range. This is helpful in diagnosing sensor operation and installation.

Accuracy: ±0.041 m³/m³ (±4%) typical 0 to 50°C (32° to 122°F); ±0.020 m³/m³ (±2%) with soil specific calibration.
This is a system level accuracy specification and is comprised of the ECH2O probe's accuracy of ±0.04 m³/m³ typical (±0.02 m³/m³ soil specific) plus the smart sensor adapter accuracy of ±0.001 m³/m³ at +25°C (+77°F). There are additional temperature accuracy deviations of ±0.003 m³/m³ / °C maximum for the ECH2O probe across operating temperature environment, typical <0.001 m³/m³ / °C. (The temperature dependence of the smart sensor adapter is negligible.)

Resolution: ±0.0004 m³/m³ (±0.04%)

Soil Probe Dimensions: 254 x 32 x 1.0 mm (10 x 1.25 x 0.04 in.)

Weight: 200 grams (7.0 oz)

Decagon ECH2O Probe Part No.: EC-20

Sensor Operating Temperature: 0° to +50°C (+32° to +122°F).
While the sensor probe and cable can safely operate at below-freezing temperatures (to -40°C/F) and up to +75°C (+167°F), the soil moisture data collected at these extreme temperatures is outside of the sensor's accurate measurement range.

Bits per Sample: 12

Volume of Influence: 0.25 liter (8.5 oz)

Sensor Frequency: 5 MHz

Number of Data Channels: 1 (A single smart sensor-compatible HOBO logger can accommodate 15 data channels and up to 100 m (328 ft) of smart sensor cable (the digital communications portion of the sensor cables)

Measurement Averaging Option: No

Cable Length Available: 5 m (16 ft)

Length of Smart Sensor Network Cable: 0.5 m (1.6 ft)

Documentation for the S-SMA-M005

The following are associated resources for this product. In general users of this product can gain insight into its possible use by utilizing the resources below.