Measurement Divergence
Measurement deviations observed when a sensor returns to a specific set point from different directions constitute a specific form of repeatable error. This calibration hysteresis occurs because the physical state of a sensing element depends on its immediate history. If a pressure transducer is tested from zero to full scale and then back to zero, the recorded values at the midpoint may differ.
Physical Source
Internal friction within materials or residual magnetism in inductive components prevents the system from following the same path during ascending and descending cycles. This calibration hysteresis is quantified by comparing the output values.
Error Bound
Manufacturers define the maximum allowable gap between these paths as a percentage of the full output span. Verification involves multiple cycles across the entire operational range to ensure the calibration hysteresis remains within the specified tolerance while environmental factors like humidity or temperature fluctuations are held constant to prevent interference. If the gap exceeds the limit, the sensor is rejected.
Calibration labs often conduct these tests at the nominal operating temperature to isolate the mechanical lag from thermal expansion effects.
Correction Method
Mathematical modeling can compensate for the known lag if the sensor path is tracked continuously. Advanced algorithms map the historical states to predict the offset caused by calibration hysteresis. This software-level adjustment improves the accuracy of the measurement system.
High-precision instruments often require such compensation to maintain linearity across the full operating window.
