Evaluating Temperature Coefficient Wander in Thin Film Platinum Resistance Elements
Evaluating temperature coefficient wander in thin film platinum RTDs requires tracking substrate strain, glass passivation diffusion, and multi-point calibration.
Sensor Aging Drift
Temporal Instability
Long-term degradation of a transducer’s output under constant environmental conditions represents a major challenge for continuous monitoring systems. This phenomenon, referred to as sensor aging drift, is characterized by a slow, unidirectional shift in the zero-point or sensitivity of the device. It occurs as the physical and chemical properties of the active materials change over time.
Material Degradation
Oxidation of metallic film resistors or the slow diffusion of dopants in semiconductor substrates alters the electrical properties of the sensing element. During sensor aging drift, these microscopic alterations alter the response curve of the device. This degradation is often accelerated by exposure to elevated temperatures.
Calibration Deviation
Measurement uncertainty increases as the device output moves away from its initially calibrated state. The sensor aging drift introduces errors that cannot be corrected without a physical calibration check against a known standard. Laboratories must establish a routine schedule to verify the sensor performance, as ignoring this drift can lead to out-of-tolerance conditions in critical industrial processes.
These checks ensure the integrity of the collected data.
Mitigation Procedure
Burn-in testing or pre-aging of the sensors before final calibration is used to reduce the rate of drift during actual use. This process forces the initial rapid phase of aging to occur in the factory rather than in the field. Consequently, the sensor exhibits a much more stable output during its service life.