Onset HOBO MX800 Series Water Data Loggers

HOBO MX800 Series wireless data loggers work with interchangeable sensors to provide a highly configurable solution for monitoring water conductivity/salinity, temperature, level, and dissolved oxygen.


  • Submersible and direct read options available
  • Wireless data offload via Bluetooth 5.0 and HOBOconnect mobile app
  • Water detect feature indicates when logger was out of the water
Starting At $495.00

HOBO MX800 Series wireless data loggers work with interchangeable sensors to provide a highly configurable solution for monitoring water conductivity/salinity, temperature, level, and dissolved oxygen. Available in both an easy-to-deploy, fully submersible model (MX801) and a direct read model (MX802) for convenient data offload that doesn’t require having to remove sensors from the water.


  • Compatible with interchangeable Conductivity, CTD (conductivity/temperature/depth), and DO sensors (sold separately) - swap out sensors for different applications
  • Bluetooth, for easy logger configuration and data offload
  • Easy to deploy, fully submersible (MX801)
  • Direct read for convenient data offload (MX802)
  • Logger diameter is less than 2 inches
  • Faster data offload via Bluetooth 5.0
  • Water detect feature indicates when logger was out of the water (MX801)
  • Barometric pressure sensor included (MX802)
  • Connect two sensors to one logger to get measurements like salinity adjusted DO directly, with no need for post processing
  • Guided calibration ensures accurate data
  • User-replaceable batteries
MX801 and MX802  
Operating Range -40° to 50°C (-40° to 122°F), cannot be frozen in ice
Radio Power 1 mW (0 dBm)
Transmission Range Approximately 30.5 m (100 ft) line-of-sight
Wireless Data Standard Bluetooth 5
Maximum Number of Sensors 2
Maximum Cable Length 120m (400 ft)
Logging Rate 5 second to 18 hours
Logging Modes Fixed interval (normal or statistics), burst, or multiple intervals with up to 8 user-defined logging intervals and durations, with pause and repeat options
Start Modes Immediate, next interval or date & time
Stop Modes Memory full, never stop (overwrite oldest data), date & time, or after a set logging period
Water Detect Events are logged when logger is submerged or removed from the water (MX801 only)
Time Accuracy ±1 minute per month 0° to 50°C (32° to 122°F)
Battery Four AA, 1.5 V lithium batteries, user replaceable
Battery Life With W-CTD or W-CT sensors: 2 years, typical with 1-minute logging interval or slower
  With W-DO sensor: 1-year, typical with 5-minute logging interval or slower
  Faster logging or statistics sampling intervals, entering burst logging mode, excessive readouts, and remaining connected with the app will impact battery life
Memory 730,000 measurements, divided between channels (4 Mbyte memory)
Data Download Time (Bluetooth 5) Full memory: Approximately 3.5 minutes
  120,000 measurements: 1 minute
  May take longer the further the device is from the logger
Dimensions Logger diameter: 4.14 cm (1.63 inches)
  Length without sensor: 20 cm (8 inches)
  Length with W-CTD sensor: 36 cm (14 inches)
  Length with W-CT sensor: 33 cm (13 inches)
  Mounting loop: 12.7 x 22.6 mm (0.5 x 0.89 inches)
Weight Approximately xx g (xx oz) in air; approximately xx g (xx oz) in saltwater
Wetted Materials Logger: PVC housing with polyester film label, PET sensor connector end cap and mounting handle with EPDM and Buna-N O-rings, passivated 316 stainless steel hardware rated for use in saltwater; MX802 also has ePTFE vent
  Collar: HDPE, titanium screws
  Note: logger should be mounted so that no metal parts of the logger are in contact with other metals
Environmental Rating MX801: IP68; waterproof to 100m (with sensor(s) attached)
  MX802: IP67, NEMA 6; Weatherproof (with cable or Termination Plug attached); this model is not waterproof
MX802 Barometric Pressure  
Measurement & Calibrated Range 66 to 107 kPa (9.6 to 15.5 psia), -20° to 50°C (-4° to 122°F)
Accuracy* Typical error: ±0.2 kPa (0.029 psi)
  Maximum error: ±0.5 kPa (0.073 psi)
Resolution <0.01 kPa (0.0015 psi)
Pressure Response Time** <1 second to 90% at a stable temperature
Contribution to Water Level Accuracy*** Typical error: ±0.075% FS, 0.3 cm (0.01 ft) water
  Maximum error: ±0.15% FS, 0.6 cm (0.02 ft) water
*Pressure Accuracy: Absolute pressure sensor accuracy includes all sensor drift, temperature, and hysteresis-induced errors. 
**Changes in Temperature: Allow 20 minutes in water to achieve full temperature compensation of the pressure sensor. There can be up to 0.5% of additional error due to rapid temperature changes. 
***Water Level Accuracy: With accurate reference water level measurement, known for water density, and a stable temperature environment. System Water Level Accuracy equals the sum of the Barometric Water Level Accuracy plus the selected CTD sensor Water Level Accuracy. 
  • (1) HOBO MX800 data logger
  • (1) Coupler
  • (1) 3/32" Allen wrench
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