What Sensor Calibration Is and Why Readings Drift
Calibration maps sensor error against traceable standards, while drift stems from physical aging, mechanical strain, and environmental stress over time.
Platinum RTD Aging
Resistance Stability
Temperature sensors made from high-purity platinum wire or thin films exhibit a very predictable change in resistance as they heat or cool. Platinum rtd aging refers to the slow, permanent shift in the base resistance of the sensor that occurs after prolonged exposure to high temperatures or thermal cycling.
Material Stress
Mechanical strain develops between the platinum element and its ceramic substrate because they expand at different rates when heated. Over time, this stress leads to platinum rtd aging as the metal lattice develops defects or the wire undergoes grain growth. These internal changes cause the sensor to read slightly higher or lower than its original calibrated value, which introduces a growing error in the temperature measurement system.
Drift Quantification
Metrologists measure this phenomenon by comparing the sensor against a primary standard after months of field use. Stability specifications for platinum rtd aging are typically expressed as a fraction of a degree Celsius per year under specific operating conditions.
Sensor Selection
High-grade sensors undergo a pre-aging process where they are cycled through extreme temperatures to stabilize the platinum before final calibration. Minimizing platinum rtd aging is necessary for precision control in chemical processing and laboratory environments.