Editing Precision Thermocouple Based Temperature Measurement System (section)

=== 4.3. Anomalous Behaviour Beyond ΔT = 14°C ===
[[File:anomaly.jpeg|thumb|center | 800px]]

Within the primary measurement window of ΔT = 1°C to 14°C, the output voltage increased monotonically from approximately −71 μV toward less negative values with increasing temperature difference, consistent with the linear thermoelectric response characterised in Section 4.2. At ΔT = 14°C, the output voltage reached a maximum of approximately −61.5 μV.
Beyond this point, a departure from the established trend was observed. At ΔT = 16°C, the output voltage reversed direction, falling back to approximately −63.5 μV rather than continuing to increase. This behaviour was reproduced consistently across repeated measurements conducted under identical conditions, confirming that the reversal is a systematic feature of the pellet's response and not attributable to instrumentation noise, contact instability, or measurement artefact. The onset of this anomalous behaviour at ΔT = 14°C therefore defines the practical upper limit of the linear operating window for this measurement configuration. All primary data used for Seebeck coefficient extraction were accordingly restricted to ΔT ≤ 14°C. The physical mechanisms underlying this behaviour are examined in Section 5.3.