A Fe-C eutectic cell for thermocouple calibration was manufactured and tested to investigate its phase transition characteristics in the thermocouple thermometry. It was observed that the freezing plateaus were strongly affected by the freeze-inducing temperature $T_{f}$. In case of the melting process, the melting plateau was influenced by the previous thermal history. As $T_{f}$. in the previous freezing was lower, the melting plateau became lower with a temperature dependence as small as $-0.0015^{circ}C/^{circ}C$. Therefore, it was found that the freeze-inducing temperature should be fixed to obtain a reproducible phase transition temperature in the melting. After fixing $T_{f}$, the melting process was examined and it was found that long and flat melting plateau was obtained within a reproducibility of about ${pm}0.01^{circ}C$. Based on the observed results, it was recommended that Fe-C eutectic temperature be best realized for the melting process with a melt-inducing temperature of $+3^{circ}C$ above the expected liquidus temperature after freezing at $-5^{circ}C$ below the solidus temperature.