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US 5,430,384 AGranted
Temperature compensated soil moisture sensor
AssigneeOnset Computer Corporation
InventorLon Hocker
Life of this patent
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Abstract
A resistive soil moisture sensor which is implanted in the soil includes a temperature sensitive component, located at the same soil depth as the sensor. The thermistor is part of a thermistor network which includes other components which are located above ground. The resultant sensor automatically compensates for temperature variations, and is well suited for use with data loggers and automatic control systems.
Claims4
A temperature compensated soil moisture sensor for measuring soil moisture content in soil surrounding said sensor at a given depth in the soil, which comprises:
- a moisture permeable housing;
- a moisture permeable electrode matrix disposed within said housing such that soil moisture passes from the soil, through said housing, and into said electrode matrix;
- a first electrode connected to said electrode matrix;
- a second electrode connected to said electrode matrix such that a resistance measured between said first and second electrodes is indicative of soil moisture content in the soil surrounding said sensor;
- and
- means for compensating for changes in the resistance between said first and second electrodes caused by changes in soil temperature, said temperature compensation means consisting of a thermistor and a plurality of resistors connected to said first electrode such that said thermistor is located at substantially the same depth in the soil as said electrode matrix when said soil moisture sensor is in use, said compensating means not including an arithmetic divider;
- whereby an existing soil moisture sensor can be easily retrofitted with temperature compensation by potting said thermistor in a top end cap of the existing sensor.
4 more elements
Dependencies are inferred from the claim text.