MP406 and MP306 ADR Standing Wave Technology Soil Moisture Sensors

The MP306/MP406 Soil Moisture Sensor is a robust, long term soil moisture measurement sensor that measures volumetric soil water content using Amplitude Domain Reflectometry (also knowns as standing wave technology). It can be calibrated to provide accuracy within ±1%, and using the standard calibration curves ±3%.

• Measures soil water content, independent of soil temperature or salinity
• Voltage and 4-20mA versions available
• Robust for long term installation in research or commercial applications

Available in several configurations, and compatible with the ICT International IoT MFR Node, this sensor is suitable for deployment in both research and management projects:

• MP406: bare ended sensor, voltage output.
• MP306: bare ended sensor, voltage output; due to its needles arrangement is suitable for laboratory soil columns applications, or greenhouse pots.
• MP406C-12V: 4-20mA sensor, 12V.
• MP406C-24V: 4-20mA sensor, 24V.

Details on the MPKit that uses the MP306 or MP406 sensor can be found here.

About the sensor

MP406 and MP306 Soil Moisture Sensor Features

• Volumetric Soil Water Content (%) or can simultaneously measure soil water potential
• Highly accurate and precise
• Robust, stainless steel needles and epoxy body
• Measures in saline, toxic and high temperature soils
• Rapid measurement
• Can be buried for up to 20 years

Research papers using the MP406 Soil Moisture Probe can be found here.

These sensors have a reinforced body and stainless steel needles making it ideal for use in extreme environments such as mine sites, landfills and saline soils as well as standard agricultural soils The measurements are not affected by temperature or salinity. Both MP406 or MP306 can be used to take continuous measurements over time through permanent or temporary burial and connection to an IoT Node

MP406 and MP306 use Amplitude Domain Reflectometry, equivalent to a Time Domain Reflectometry (TDR) sensor without the need for a complex and expensive pulse generator; high accuracy, precision sensor with +/- 1%VWC accuracy following soil-specific calibration and 0.01%VWC resolution.

Accuracy

Amplitude Domain Reflectometry and hence the MP406 are not affected by changes in temperature or salinity of the soil or material being measured and hence the values of VSW% are equivalent to oven dried water content.

What is Amplitude Domain Reflectometry (Standing Wave)?

Amplitude Domain Reflectometry uses an oscillator to generate an electrical field in order to detect the dielectric properties of a substrate of interest. The parallel needles of an MP406 act as a coaxial transmission line to generate a signal. The amplitude of the signal is related to the dielectric constant which in turn is directly related to moisture content.