Fig. 1. Time domain reflectometry (TDR) waveforms of the thermo-TDR probe in water, in air, and shorted at the cylinder base in air. L₀ is the distance of the first reflection determined by shorting at the cylinder base in air. L_w is the distance of the second reflection calibrated in distilled water. The two dashed lines near the water curve are tangent lines used to determine the end of probe reflection position.