Data Loggers & Remote Monitoring Solutions

Onset HOBO MX pH and Temperature Data Logger

The HOBO MX pH and Temperature logger is designed for long-term monitoring of pH in aquatic systems. With a replaceable pH electrode and an anti-biofouling copper guard, this durable logger can be deployed in both fresh and saltwater environments. This logger is Bluetooth® Low Energy (BLE)-enabled for wireless communication with a mobile device or computer. Using the HOBOconnect® app, you can easily calibrate and configure the logger, download logged data to your phone, tablet, or computer, or automatically upload the data to HOBOlink® for further analysis. You can also configure the logger to calculate statistics, set up alarms to trip at specific thresholds, or enable burst logging in which sensor readings are logged at a faster interval when the pH or temperature rises above or falls below certain limits.

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Designed for long-term monitoring of pH in estuaries, lakes, streams, rivers, and oceans. This logger leverages Bluetooth technology to communicate wirelessly with Onset’s free HOBOconnect app running on your mobile device or Windows computer, making logger setup, calibration, and data offload quick and easy. Plus, a guided pH calibration process in the HOBOconnect app makes an otherwise complicated process easier to follow. This affordable, compact logger delivers high resolution data and dramatically cuts the time and effort needed to collect it.


  • Guided pH calibration following on-screen prompts in HOBOconnect app
  • Rugged PVC housing for deployment in both freshwater and saltwater environments
  • Quick and easy data offload via Bluetooth to mobile devices or Windows computers
  • Water detection system for longer battery life and less maintenance
  • Potentiometric pH electrode with plastic body, gel electrolyte, and double cloth junction
  • User-replaceable battery, pH electrode, and anti-biofouling copper guard
  • Accuracy of ±0.10 pH units within ±10°C of temperature at calibration

What’s In The Box

  • MX2501 pH and Temperature Data Logger
  • pH electrode
  • Bottle of storage solution that can also be used as a storage container for the electrode
  • Anti-biofouling copper guard
  • Tube of silicone grease
  • AA battery

Introducing Onset HOBO MX pH and Temperature Data Logger