This paper highlights results from Onset's tests of the HOBO Water Level logger and comparable loggers from two competitors. Vendors specify water level data loggers in different ways, and we felt it would be valuable to compare accuracy under identical test conditions. All loggers tested have a 30-ft measurement range. Our testing concluded that while the data loggers have similar accuracy at a fixed temperature, the HOBO Water Level Logger had significantly better accuracy when there were changing temperatures. See the detailed test results below.
|Vendor's Specified Accuracy:|
|Accuracy at a Constant Temperature|
|We tested the water level loggers in a constant temperature environment to collect data for accuracy deviation over a range of depths.
The HOBO® Water Level logger performed well in this test. The worst case error for the HOBO logger was 0.013 feet, while the worst case errors for the competitive loggers were 0.016, 0.027 and 0.029 feet respectively.
|Temperature Compensation Accuracy|
|Accurate performance over temperature is particularly important for applications with varying water temperatures, such as streams, wetlands and tidal areas. We tested the water level loggers for accuracy across a range of temperatures.
The worst case error for the HOBO® Water Level logger in this test was 0.010 feet, while the worst case errors for the competitive loggers were 0.100, 0.023 and 0.077 feet respectively.
The HOBO was within its accuracy specification across the full range of temperatures tested, measuring 10 times more accurately than the Competitor 1 logger at 35 °C.
|Barometric Pressure Logger Accuracy|
We tested the HOBO® Water Level Logger's barometric pressure sensor against dedicated barometric pressure loggers from both competitors. The graph to right shows the stability of the HOBO Water Level logger's sensor over the same range of barometric pressure as those dedicated loggers.
Measuring accurately over temperature is particularly important for barometric pressure loggers, since air temperatures can vary widely. When tested, the HOBO logger had accuracy similar to that of the two competitors' dedicated barometric pressure loggers when tested at a constant temperature.
For the temperature test, the HOBO and Competitor 2 had similar accuracy (0.0085 and 0.0095 feet of error respectively), while the logger from Competitor 1 had over twice as much error (0.0215 feet).
|Other Advantages of the HOBO Water Level Logger:
The HOBO Water Level Logger has Guaranteed Accuracy
Onset guarantees the accuracy performance of HOBO U20 Water Level Loggers by providing a 3-point calibration certificate with every logger, showing measured accuracy versus a NIST-traceable standard.
The HOBO Water Level Logger uses a Robust Sensor
The HOBO U20 Water Level Logger uses a ceramic sensor, while Competitor 1's logger uses a stainless steel sensor. Stainless steel sensor diaphragms are the thickness of aluminum foil and are sensitive to any kind of shock. Even the shock from hitting water too hard can be enough to damage this type of diaphragm. Stainless steel sensors can also be damaged in freezing water, while ceramic sensors survive and continue to operate once the water thaws. Ceramic sensors are also suitable for use in salt water, while stainless steel sensors will corrode. Competitor 1's logger housing is protected by a zirconium coating; however, if scratched, this will actually increase the corrosion of the underlying stainless steel. For loggers that will be deployed in a corrosive environment, the best option is the titanium version of the HOBO Water Level Logger.
The HOBO Water Level Logger has a Factory-replaceable Battery
The competitive loggers’ batteries are not replaceable. Although the competitive loggers claim a 10-year battery life, when they are used at fast sampling rates or at higher temperatures, their batteries can be depleted in months vs. years.
The HOBO Water Level Logger is part of the HOBO System
This means that the same HOBO data shuttles and HOBOware software can be used with data loggers for water level, temperature, rainfall, soil moisture, weather, etc.
The HOBO Water Level Logger has direct USB interface
The HOBO Logger's Optic USB interface allows for easy offload of the logger in less than 30 seconds, with direct connection to USB ports on a PC or Mac. The Competitor 1's logger uses a serial interface, which greatly increases the time required to download data from loggers. Although a serial-to-USB converter can be used to achieve USB communication, this is a more cumbersome approach and is still limited by the logger's serial communication speed.
Easy Import of Barometric Pressure Data
The HOBOware Barometric Compensation Assistant accepts barometric data from another HOBO Water Level Logger, a HOBO Weather Station or HOBO Micro Station, or text data from a nearby weather station.
HOBO Loggers are Proven in Field Use
Used in more than one million deployments worldwide, HOBO data loggers have earned a reputation for reliable operation in harsh field conditions.
Data File Compatibility
HOBOware software is compatible with all HOBO Water Level Logger files and allows import of data from other manufacturers' water level loggers as well.
The HOBO Water Level Logger is the Best Value
The HOBO Water Level Logger is priced below competitive loggers, which allows for deployment of more loggers for your project.