4-20 mA current soil volumetric water content sensor


  • Low cost, accurate and reliable 4-20 milliamp (mA) sensor
  • Measure calibrated soil volumetric water content or moisture
  • Ideal for soils or substrates in the field, glasshouse, pots, or laboratory
  • Manufactured by METER Group (formally Decagon Devices)

The MAS-1 is a low cost, ruggedized sensor for the measure of soil volumetric water content with a current, 4-20 mA (milliamp) output. The MAS-1 can accurately measure the moisture content in soil or soilless media.

The MAS-1 is ideal for scientific researchers, growers, nurseries, and glasshouses with pots or artificial substrates. The robust sensor design, plus flexible output to connect to most data loggers or systems, makes the MAS-1 ideal for monitoring water content.

The MAS-1 is sensitive across the entire water content range. It can be installed in dry desert soils or in very wet peat. Sensitive to small changes in water content anywhere from 0 - 100% VWC.

The MAS-1 can be connected to any data acquisition device that supports current, or 4-20 mA, output.


sensor measurement zone dimensions

METER Group MAS-1 4-20 mA sensor


further information

METER Group EC-5 Sensor in the FieldThe MAS-1 4-20 milliamp sensor is the first current-based sensor to use METER’s trademark 70 MHz technology. This sensor offers a standard 4-20 milliamp output that is common with PLCs and irrigation controllers.  With the 4-20 mA interface, cable lengths over 250 feet are possible.

Research-grade accuracy

The MAS-1 determines volumetric water content (VWC ) by measuring the dielectric constant of the media using capacitance/frequency domain technology. The sensor uses a 70 MHz frequency,  which minimizes salinity and textural effects, making the MAS-1 accurate in almost any soil or soil-less media. Factory calibrations are included for mineral soils, potting soils, and rockwool.

Low cost individual sensors for large sensor networks

The MAS-1 delivers research-grade accuracy at a price that makes large sensor networks economically practical. You can adequately characterize your site with sensors at multiple depths and locations, even if you’re on a tight budget.





feature specification
output 4-20 mA (current, milliamp)
power input 12-32 VDC continuous
over protection yes
settling time 4 seconds
wiring Red Wire: (+) supply Black Wire: (-) output Shield: not connected
sensor type volumetric water content
measurement range 0-100% VWC typical
resolution depends on current measurement (data acquisition) device
accuracy ±6% VWC with generic calibration for supported growing media up to 65% VWC, above which accuracy lessens. Increased accuracy can be achieved with a medium-specific calibration.
sensor measurement interval 1 second
operating temperature -40 to 60 °C
dimensions 8.9 cm x 1.8 cm x 0.7 cm
cable 5 m (default) | other lengths available upon request
warranty 1 year

manual & docs

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