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Irrometer 900M-O Watermark Monitor (No Sensors)

Price $657.98
Minimum Purchase:
1 unit

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900M-O Watermark Monitor Only (without sensors) | Watermark Soil Moisture Sensors by Irrometer

  • The 900M Monitor is a battery operated data-logger, that automatically reads up to eight sensors (sold separately). 
  • Users can view readings on the screen, download data to a laptop, or use our Data Shuttle to transport the information to a computer.
  • The 900M Monitor accepts WATERMARK soil moisture sensors, soil and air temperature sensors, switch closure sensors, rain gauge, and IRROMETER RSU’s.
  • Also available as three Monitor Packages with sensor combination options.

The WATERMARK Monitor is the standard wired version of our data logger, providing users with a reliable, simple, and effective means of collecting information. Individual sensor readings display on the Monitor and can be taken at any time manually, allowing you to make on the spot checks as necessary for scheduling purposes while periodic readings are being taken to record the performance history.

Record soil moisture, soil temperature, switch positions, and rain gauge counts for an accurate record of the performance of your irrigation schedule. IRROMETER switching pressure gauges are used as switch position sensors to indicate when the system pressure is on and off to display the irrigation events. Temperature compensation of the soil moisture reading is automatic by using one or more temperature sensors or programming a default value. The IRROMETER Model RSU (4-20mA transducer) can also be read (wiring adapters and auxiliary sensor power required). 

Spring-loaded terminal strips are provided for sensor connections, which allow for easy installation and never need tightening. Data can be downloaded directly to a computer via USB, a handheld Data Shuttle (PN 900DS), or optionally sent to the web for access anytime, anywhere.


  • Automatically reads sensors at a selectable interval
  • 8 sensor capacity, can read:
    • WATERMARK Soil Moisture Sensors
    • Temperature Sensors
    • Tipping Bucket Rain Gauges
    • 4-20 mA Current and 0-5 Voltage output IRROMETER Tensiometers (RSU-C and RSU-V with Adapter)
    • On/Off switch states
    • Sensors sold separately (also available as monitor and sensor packages)
  • WaterGraph Software included (Windows only)
  • In-field display of current and recent readings
  • Download history to a computer
  • Outdoor mount
  • 9 Volt battery included
  • Weatherproof enclosure with two strain relief fittings for wiring connections, predrilled mounting hole pattern
  • USB Connectivity

Stored readings are downloaded to a computer for display. Other display options are available. The software, included with the WATERMARK Monitor, is used to set up your individual site profile, launch the data-logger, download recorded history and graphically display the results. The data file created can also be opened by some spreadsheet or graphing programs, like Microsoft Excel®.

 Irrometer 900M-O Watermark Monitor (No Sensors)

Irrometer 900M-O Watermark Monitor (No Sensors)