Everything you need to know about HOBO Salinity Loggers

Conductivity and salinity levels are proven indicators of environmental water quality. This relationship makes salinity loggers an essential tool for scientists, public health officers and environmentalists who need dependable data to gain insights into the health of waterways for water management or scientific research purposes.

Hobo’s series of salinity loggers meet all the rigours that scientific instruments must endure when monitoring aquatic environments to produce reliable data. By popular demand, we have undertaken a comprehensive analysis of Hobo’s Salinity Loggers, including examples of use, product benefits and the essential specifications.

The Correlation Between Conductivity, Salinity and Water Quality Explained

Conductivity, specifically specific conductance, is a measure of a solution’s ability to conduct electricity. Salinity is a measure of the concentration of salt ions, which impacts a liquid’s ability to conduct electricity. Most water bodies maintain fairly constant salt concentrations (and therefore) conductivity.Significant environmental change due to events such as flooding, evaporation or man-made pollution can affect this equilibrium, often with detrimental impacts on water quality and therefore the health of various forms of biotic and abiotic life.

HOBO U24 Salinity Logger Series Features

Salinity Logger Use

There are two types of HOBO salinity logger within the 'U24' series that measure conductivity (and temperature). To obtain a salinity reading, the HOBO salinity loggers measure the conductivity of water then convert the result to a salinity measurement using the Practical Salinity Scale 1978 (PSS-78).

Sensor Features

The sensors on the U24 loggers feature a titanium pentoxide coating that protects them from direct contact with the measured water. This coating gives HOBO salinity loggers the upper-hand over traditional electrode-based, full-contact conductivity loggers. Without direct contact, Hobo’s sensors won’t tarnish and corrode at the same rate. The coated sensor area is open, so if any tarnishing or fouling does appear after prolonged use, cleaning will be straightforward.

Data Logger Housing

The outer housing of the U24 series of HOBO salinity loggers consists of sturdy Delrin plastic, epoxy, a stainless steel retaining ring, polypropylene, Buna rubber O-ring and titanium pentoxide (the inert coating over the sensor). These materials are ideally suited to withstand the harshness of long-term saltwater exposure.

Data Retrieval and Analysis

The U24 series of salinity loggers require HOBOware Pro software and either HOBO Waterproof Shuttle or the Base-U-4 Optic USB Base Station for secure and reliable data retrieval. The HOBOware Pro software enables start/end-point calibration to compensate for any fouling and provides easy conversion to specific conductance and salinity measurements using the Practical Salinity Scale 1978 (PSS-78). View the features and available functions of HOBOware Pro in the table below:

U24 Series Salinity Logger

	Conductivity-Salinity Data Logger (For Fresh Water) Specifications	Conductivity Data Logger - U24-002C  Specifications
Measurements:	Conductivity, Temperature, HOBOware Pro software provides easy conversion to specific conductance and salinity.	Conductivity, Temperature, Calculated specific conductance at 25°C, Salinity (calculated using PSS-78).
Conductivity Measurement Range:	Low Range: 0 to 1,000 μS/cm Full Range: 0 to 10,000 μS/cm	Low Range: 100 to 10,000 μS/cm High Range: 5,000 to 55,000 μS/cm
Temperature Measurement Range:	5° to 35°C
Specific Conductance Accuracy:	Low Range: 3% of reading, or five (5) μS/cm Full Range: 3% of reading, or 20 μS/cm, whichever is greater	Low Range: 3% of reading or 50 µS/cm, whichever is greater  High Range: 5% of reading, in waters within a range of  ±3,000 µS/cm; waters with greater variation can have substantially greater error
Resolution:	Conductivity: 1 μS/cm Temperature: 0.01°C	Conductivity: 2 uS/cm  Temperature: 0.01°C
Conductivity Drift:	Less than 3% sensor drift per year	Up to 12% sensor drift per month (exclusive of drift from fouling). Monthly start- and end-point calibration should be used with the HOBOware Conductivity Assistant to achieve the specified Specific Conductance accuracy.
Response time:	1 second to 90% of change (in water)
Operating Range:	-2 to 36°C (non-freezing)
Memory:	18,500 temperature and conductivity measurements when using one conductivity range; 14,400 sets of measurements when using both conductivity ranges.
Sample rate:	1-second to 18 hrs, fixed or multiple-rate sampling with up to 8 user-defined sampling intervals.
Battery life:	Three years of battery life when operated at 1-minute logging intervals.
Maximum Depth:	70 metres

Conclusion

HOBO has designed salinity loggers that withstand extended periods in tough aquatic environments and meet all the requirements for water management and scientific research.

Want more information on the HOBO U24 series of salinity loggers? Speak with an Instrument Choice Scientist! We're here to help! Call 1300 737 871 or email [email protected].