Designed for long-term monitoring in estuaries, lakes, streams, rivers, and oceans, this logger measures pH and water temperature. Bluetooth Low Energy® (BLE) connectivity allows the logger to communicate wirelessly with iOS devices through the free HOBOmobile® App. Use the app for easy logger setup, step-by-step calibration, and fast data offload. The logger's 152 KB memory stores up to 43,300 measurements. Equipped with a rugged PVC housing, the logger is waterproof to 40 meters (131.2 feet) and can be deployed in freshwater or saltwater environments. The pH electrode features Pellon® junctions, gel electrolyte, and a glass sensor bulb..

- pH Range: 2.00 to 12.00
- Temperature Range: -2°C to 50°C (28.4°F to 122°F).
- Accuracy pH:, ±0.10 pH units within ±10°C of temperature at calibration; 
- Accuracy Temperature: ±0.2°C (±0.36°F). 
- Resolution pH: 0.01; 
- Resolution Temperature: 0.024°C at 25°C (0.04°F at 77°F). 
- Response Time pH: 1 minute typical to 90% at constant temperature in stirred water; 
- Response Time Temperature: , 7 minutes typical to 90% in stirred water. 
- Operating Range: -2°C to 50°C (28.4°F to 122°F), non-freezing. 
- Transmission Range: Approximately 30.5 m (100 feet) line-of-sight in air. 
- Logging Rate: 1 second to 18 hours. 
- Battery Type: One AA 1.5V. 
- Environmental Rating: IP68. 
- Dimensions: 9" x 1.68". 
- Weight: 9.46 oz.

The HOBO MX2501 data logger requires the  and a compatible mobile device. The system requirements for the HOBOmobile app can be found at the bottom of the