Meaning
The predictable, gradual change over time in the electrical resistance characteristics of a temperature-sensing element caused by material changes affects the long-term drift of the sensor. Assessing the thermistor aging rate determines how frequently a marine temperature sensor must be recalibrated to maintain its specified accuracy. This process of drift occurs as the internal semiconductor material stabilizes after manufacturing and during prolonged exposure to cold seawater.
It represents a primary source of measurement uncertainty in oceanographic profiling instruments.
Maintenance Routine
Sea-going research institutions must establish regular schedules to offset this natural drift. The thermistor aging rate is calculated by comparing the sensor’s output against a triple-point-of-water cell before and after each deployment. This procedure allows technicians to apply a time-dependent correction to the collected dataset.
If the sensor drift exceeds the allowed threshold, the thermistor must be replaced or returned to the factory for long-term stabilization.
Contractual Specification
Supplier contracts for deep-sea sensors often include a guaranteed maximum value for this physical change. The thermistor aging rate is specified in millikelvin per year under standard operating conditions. If the sensor exceeds this rate during the warranty period, the buyer is entitled to a free replacement or recalibration.
This guarantee protects research programs from instruments that degrade too quickly to be useful for climate monitoring. It also ensures that the manufacturer maintains strict quality control over the sourcing of their semiconductor elements.
Calibration Frequency
High-accuracy studies require that sensors be calibrated at least once a year. Sensors with a low thermistor aging rate can be left in the water for longer periods without sacrificing data quality. This longevity reduces the overall operational cost of autonomous monitoring networks.
