Decagon MAS-1 4-20 Milliamp Soil Moisture Sensor.

4-20 Milliamp Output, Ultra-Long Cable Lengths.

The MAS-1 4-20 milliamp sensor is the first current-based soil moisture sensor to use Decagon'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

Like other Decagon soil moisture sensors, the MAS-1 measures soil moisture accurately without the sensitivity to electrical conductivity and variation in soil types that have plagued inexpensive sensors in the past.

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. And the MAS-1's ultra-long cable lengths give you even more flexibility to put your sensors where you want them.

Reasons to pick the MAS-1

  • If you need a 4-20 milliamp sensor
  • If you need cable lengths greater than 250 feet

Engineered for 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.

Interface Standard 4-20 mA analog transmitter
Supply Voltage 10-32 VDC continuous
Output Current 4 - 20 mA
Overvotage  Protection Yes
Settling Time 4 seconds
Wiring Red Wire: (+) supply
Black Wire: (-) output
Shield: not connected
Type Volumetric water content (VWC)
Range 0-100% VWC typical
Resoultion Depends on current measurement (data aquistion) 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 mediumspecific calibration.
Output 4-20 mA current proportional to VWC
Sensor Measurement Interval 1 second
Operating Enivornment Temperature -40 to 80°C
Physical Properties Dimensions 8.9 cm x 1.8 cm x 0.7 cm
Cable 5 m, 2 wire as standard, Custom cable length available upon request
Warranty: One year, parts and labour

Non UK/Ireland Customers

Non UK/Ireland Customers, please contact Decagon Devices at:

MAS-1 Volume

These innovative sensors will enable you to monitor soil moisture accurately and affordably with a standard 2-wire, 4-20 mA analogue interface for use with many data acquisition and control systems.


*The MAS-1 cannot be used with the standard Decagon data loggers.

MAS-1 Manual
Size: 252.4 KB (258,466 bytes)

Environmental Catalogue
Size: 2.5 MB (2,581,813 bytes)

Quotation Request

Email us to request a quotation for the Decagon MAS-1 Soil Moisture Sensor.