The accuracy and precision of iButtons are model specific and are available from the manufacturer; however, the thermal properties of the PVC will have an effect on the response time. The response time was measured by submerging the entire TROD, initially at room temperature, into a section of 4-inch diameter PVC pipe in equilibrium with a temperature controlled water bath at 5.0°C. The elapsed time for the temperature to change was calculated by a linear regression of the time rate of temperature change against time. Six polyurethane sealed iButtons were attached to the outside of the TROD adjacent to internal sensors for comparison of the response and thermal time constant.
Each sensor should be calibrated. We placed the TROD into a 4 inch pipe with water circulating from a water bath. For each sensor, develop a regression equation to correct raw data. Here we used a NIST certified traceable digital thermometer (Cat 4000, Control Company) with resolution (0.0001°C) and accuracy (0.05°C). Individual iButtons in the TROD were evaluated at target bath temperatures of 5, 10, 15 and 20°C. Individual regressions were developed for each iButton sensor (6 total). Time for the trod to reach equilibrium was about 20 minutes.
Additional information about accuracy and calibration is available in the Water Resources Research article titled "A new temperature profiling probe for investigating groundwater-surface water interaction".