Decagon Devices MAS-1 Manual del usuario - Página 6

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MAS-1

About the MAS-1

The MAS-1 measures the dielectric constant of the soil in order to

ﬁnd its volumetric water content. Since the dielectric constant of

water is much higher than that of air or soil minerals, the dielectric

constant of the soil is a sensitive measure of water content. The

MAS-1 supplies a 70 MHz oscillating wave to the sensor prongs that

induces an electromagnetic ﬁeld in the medium (soil) surrounding

the sensor. The charging and discharging of the sensor is controlled

by the dielectric of the surrounding soil.

A microprocessor on the MAS-1 measures the charging of the sensor,

and therefore the dielectric constant of the soil which is related to

the water content of the soil. The microprocessor makes a dielectric

measurement and updates the transmitted current once per second.

The transmitted 4-20 mA current can be converted to the water con-

tent of the soil using a simple calibration function.

We designed the MAS-1 to be used with standard 4-20 mA con-

trollers and monitoring systems. It cannot be used with Decagon

logging systems. For more information about using Decagon logging

systems please contact Decagon's customer support representatives.

2.1

Speciﬁcations

Electrical

Interface: Standard 4-20 mA, 2-wire analog transmitter

Supply voltage: 12 to 32 VDC continuous

Output current: 4-20 mA

Overvoltage protection: Yes

Reverse polarity protection: Yes

Settling time: 4 seconds

Wiring:

2 ABOUT THE MAS-1