The importance of cross-calibration and protecting water temperature sensors against direct solar radiation heating in hydrological studies

ABSTRACT

Water temperature monitoring is important in many scientific studies. This study compares three models of water temperature sensors (Vemco Minilog II, HOBO TidbiT and HOBO Pendant) to test the importance of: (1) using cross-calibration to minimize relative errors, (2) using cross-calibration to improve on the accuracy of less accurate sensors, and (3) protecting sensors against direct solar radiation heating. The results show that when the same sensor models are cross-calibrated, the relative error can be reduced (Vemco: 0.01°C; HOBO TidbiT: 0.02°C; and HOBO Pendant: 0.07°C). Cross-calibration can also improve less accurate sensors (HOBO TidbiT and Pendant) to similar accuracies of Vemco (±0.1°C). Finally, no evidence of solar radiation heating was observed for Vemcos (unprotected); however, HOBO TidbiT and Pendant showed heating up to 2°C (maximum). When HOBO TidbiT and Pendant are shielded (flow-through system), heating is no longer an issue.