Evaluation of the Radar Stage Sensor Manufactured by Forest Technology Systems, IncorporatedResults of Laboratory and Field Testing

Two identical Radar Stage Sensors from Forest Technology Systems, were evaluated to determine if they are suitable for U.S. Geological Survey (USGS) hydrologic data collection. The sensors were evaluated in laboratory conditions to evaluate the distance accuracy of the sensor over the manufacturers specified operating temperatures and distance to water ranges. Laboratory results were compared to the manufacturers accuracy specification of 0.007 foot (ft) and the USGS Office of Surface Water (OSW) policy requirement that water level sensors have a measurement uncertainty of no more than 0.01 ft or 0.20 percent of the indicated reading. Both of the sensors tested were within the OSW policy requirement in both laboratory tests and within the manufacturers specification in the distance to water test over tested distances from 3 to 15 ft. In the temperature chamber test, both sensors were within the manufacturers specification for more than 90 percent of the data points collected over a temperature range of 40 to +60 C at a fixed distance of 8 ft. One sensor was subjected to an SDI-12 communication test, which it passed. A field test was conducted on one sensor at a USGS field site near Landon, Mississippi, from February 5 to March 29, 2016. Water level measurements made by the radar during the field test were in agreement with those made by the Sutron Accubar Constant Flow Bubble Gauge.
All initial testing was performed with RSS firmware version 1.05. A second temperature chamber test was performed on a single RSS in 2016 to verify performance with a newly released firmware version 1.09. Test results confirmed the results of the first temperature test.