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

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Affordable current-based soil moisture sensor

The MAS-1 4-20 milliamp soil moisture 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 soil moisture sensor 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 soil moisture 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.

Specifications

Interface   Standard 4-20 mA analog transmitter NOTE: Temperature measurement may not be accurate if sensor is not fully immersed in the medium of interest, due to excessively long equilibration time.
Supply Voltage 12-32 VDC continuous
Output current 4 – 20 mA
Overvoltage protection Yes
Settling time 4 seconds
Wiring Red Wire: (+) supply
Black Wire: (-) output
Shield: not connected
Sensor type Volumetric Water Content (VWC)
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.
Output 4-20 mA current proportional to VWC
Sensor measurement interval 1 second
Operating environment temperature

-40 to 60 °C
 

NOTE: Sensors can be used at higher temperatures under some conditions. Contact METER for more details.

Physical properties dimensions 8.9 cm x 1.8 cm x 0.7 cm
Cable 2 m or 5 m, 3 wire (22 AWG tinned red and black wire, 24 AWG tinned bare wire); custom cable length available upon request.
Measurement volume See comparison article

Downloads

MAS-1 Manual Manual PDF, 1.106MB
Soil sensor calibration guide Instructions PDF, 0.6MB
Sensor Wire Splicing Guide (Quick Method) Instructions PDF, 0.9MB
Sensor Wire Splicing Guide (Complete Method) Instructions PDF, 5MB

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