Onset HOBO MX2205
Onset Pendant MX2205 water temperature data logger with external sensor
HOBO Tidbit MX2205 waterproof data loggers attached to post with external sensor cable submerged is used to monitor a stream
Waterproof HOBO Tidbit MX2205 with a submersible external sensor monitoring in a cranberry bog
Part Number -


HOBO TidbiT MX External Temp Data Logger

Bluetooth logger with external sensor

$179.00 USD
A waterproof data logger with both an internal sensor and an external sensor that’s designed for monitoring fast-changing temperatures; can be deployed just above water or soil, for the most convenient wireless data download to your mobile device or laptop.

Important Information

Requires a compatible mobile device or Windows computer and the HOBOconnect app. System requirements for the app can be found at the bottom of the HOBOconnect software page.

Compatible with


The HOBO TidbiT MX2205 is ideal for monitoring shallow waters, like streams and wetlands, or for monitoring soil in fields that are prone to flooding. Equipped with both an internal sensor to monitor ambient temperature and an external sensor on a 2m cable to accurately monitor fast-changing temperatures, the HOBO TidbiT Mx2205 is a low-cost, easy-to-use, waterproof logger that leverages the power of Bluetooth to deliver high-accuracy data straight to your mobile device or Windows laptop running Onset's free HOBOconnect app. This rugged logger withstands harsh environments, and can be deployed just above water or soil for quicker, more convenient data downloads that don’t require pulling up the logger.

  • Fast temperature-response time (20 seconds)


  • External temperature sensor, plus internal sensor for ambient temp monitoring
  • ±0.2°C (±0.36°F) accuracy
  • Large memory stores 96,000 measurements
  • 3-year battery life (Bluetooth on); 5-year battery life (Bluetooth off)


  • Two mounting tabs for use with screws or zip ties ensure secure deployment
  • Convenient wireless setup and download via Bluetooth
  • Works with Onset’s free HOBOconnect app



Temperature Sensors

Probe | -40 to 100°C (-40 to 212°F), with tip and cable immersion in fresh water up to 50°C (122°F) for one year
Logger | -20° to 70°C (-4° to 158°F) in air; -20° to 50°C (-4° to 122°F) in water, maximum sustained temperature in water 30°C (86°F)
±0.25°C from -40 to 0°C
(±0.45 from -40 to 32°F)
±0.2°C from 0 to 70°C
(±0.36 from 32 to 158°F)
±0.25°C from 70 to 100°C
(±0.45 from 158 to 212°F)
±0.25°C from -20° to 0°C
(±.45°F from -4° to 32°F)
±0.2°C from 0° to 70°C
(±0.36°F from 32° to 158°F)
0.01°C (0.018°F)
<0.1°C (0.18°F) per year
Response Time
Probe | 3 minutes in air moving 1 m/sec; 20 seconds in stirred water
Logger | 15 minutes typical to 90% in air moving 1 m/s, unmounted; 4 minutes typical to 90% in stirred water, unmounted


Logger Operating Range
-20° to 70°C (-4° to 158°F)
Buoyancy (Fresh Water)
14.26 g (0.50 oz) negative
Waterproof Rating
To 30.5 m (100 ft)
Radio Power
1 mW (0 dBm)
Transmission Range
Approximately 30.5 m (100 ft) line-of-sight
Wireless Data Standard
Bluetooth Low Energy (Bluetooth Smart)
Logging Rate
1 second to 18 hours
Time Accuracy
±1 minute per month at 25°C (77°F)
CR2477 3V lithium, non-replaceable
Battery Life
3 years, typical at 25°C (77°F) with logging interval of 1 minute and Bluetooth Always Off disabled in software.
5 years, typical at 25°C (77°F) with logging interval of 1 minute and Bluetooth Always Off enabled in the app.
Faster logging intervals and statistics sampling intervals, burst logging, remaining connected with the app, excessive downloads, and paging may affect battery life.
96,000 measurements
Full Memory Download Time
Approximately 45 seconds; may take longer the farther the device is from the logger.
Wetted Materials
Epoxy case, Santoprene (TPE) boot
4.06 x 6.99 x 3.51 cm (1.6 x 2.75 x 1.38 inches)
External temperature sensor diameter: 0.53 cm (0.21 in.)
External sensor cable length: 2 m (6.56 ft.)
70.0 g (2.47 oz.)
Environmental Rating
CE Compliance Mark
United States FCC Mark
Australia/New Zealand General Compliance mark
Japanese TELEC Mark


Compatible items


$375.00 USD

MX2205 TidbiT® External Temperature Logger Manual

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