Soil Moisture Sensors

The original IRROMETER instrument was the first commerically available tensiometer, and is still the standard by which other methods are tested. Simple, reliable, and accurate, the IRROMETER continues to be the choice of many successful growers and consultants.

First introduced in 1979, the WATERMARK sensor has grown in popularity and gained acceptance worldwide for reliability and accuracy in measuring soil moisture. This Granular Matrix Sensor offers low cost, accurate readings, and easy integration with electronic reading equipment.

IRROMETER Tensiometers

Direct physical reading of soil water tension

SR Instrument
  • Light to Medium Soils
  • High Accuracy
  • Standard and Low Tension Versions Available
  • Sensitive to Medium Sensitive Crops
More Info

No maintenance, high value, granular matrix sensor

200SS Sensor
  • Medium to Heavy Soils
  • Good Accuracy
  • 30-200 cb Irrigation Range
  • Medium to Tolerant Crops
More Info

IRROMETER Tensiometers

The IRROMETER Tensiometer is the standard in accurate soil moisture measurement, offering growers an inexpensive and reliable means of measuring soil moisture for irrigation scheduling. An IRROMETER will measure the actual soil water tension, which indicates the effort required by root systems to extract water from the soil. Because the IRROMETER is a true measurement of soil water potential, the instrument is not affected by salinity and does not require site calibration.

The IRROMETER is available in several models, with standard lengths of 6", 12", 18", 24", 36", or 48" dependent on the rooting depth of the specific crop.

The "SR" IRROMETER is the standard instrument for use in medium to heavy soils. Each instrument includes a threaded replaceable tip as well as reservoir, air free gauge chamber, and membrane vented stainless steel vacuum gauge with a 0 to 100 cb/kPa soil water tension range.


The "LT" IRROMETER is fitted with a low tension 0-40 cb/kPa gauge for applications where tensions above 30 are rarely expected. Ideal for very coarse soils, sands, and non-soil containter media where soil water tension changes rapidly in the lower end of the scale.


The "MLT" (Miniature Low Tension) is designed for applications similar to the Model "LT" above where small size is required. Ideal for use with very coarse soils and non-soil container-media. Its compact size and 0-40 cb/kPa gauge make it a good choice for green house applications.

MLT Spec Sheet

OUTPUT OPTIONS: Additional options for connecting IRROMETER tensiometers to data collection or control devices are available, including switching gauges as well as 4-20mA and 0.5V to 4.5V output transducers.

Output Options

Additional Resources:

Product Brochure

90 Second IRROMETER Installation (YouTube)

WATERMARK Soil Moisture Sensors

In use since 1978, the patented WATERMARK sensor (PN: 200SS) is an electrical sensing device that is buried in the active root zone to measure soil water tension.

The sensor consists of corrosion resistant electrodes embedded within a specialized granular matrix. Water in the soil exchanges with the sensor matrix, providing a measurement of centibars (or kPa) of soil water tension equivalent to the readings from an SR or LT tensiometer.

The WATERMARK is designed to be a permanent sensor, left in the soil to be read by logging devices or handheld readers. We offer our own reading solutions, but the sensor is also widely used by industry partners in their own applications.

Product Brochure

WATERMARK Reading Tools

WATERMARK Installation (YouTube)
200SS Sensor
  •   0-200 Centibar range
  •   Stainless steel enclosure
  •   Will not dissolve in soil
  •   Not affected by freezing temperatures
  •   Internal compensation for commonly found salinity levels
  •   Inexpensive
  •   Easy to use
  •   No maintenance


Integration Options

WATERMARK sensors require a reading device designed specifically to read them. For other devices which can read standard analog sensors, we offer adapters to allow easy integration:

200SS-SDI Adapter - SDI module that reads three WATERMARK and 1 200TS Soil Temp Sensor
200SS-VA Adapter - Adapter reads one WATERMARK and outputs standard 0-3V analog signal

For directly integrating WATERMARK sensors in to your device project, our integration guide covers best practices and includes an example Arduino implementation:

WATERMARK Integration Guide
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