Injection Pen Plunger Sensing for Accurate Drug Remaining Detection

The patent replaces complex mechanical sensing mechanisms with a simpler plunger movement-based detection system. The sensor unit detects liquid amount by monitoring plunger position changes, which converts a complex liquid volume measurement problem into a straightforward linear displacement measurement, thereby improving measurement precision while controlling device complexity.

The patent implements mode switching between first mode (normal operation) and second mode (error correction) based on detected liquid amount thresholds. This dynamic adaptation allows the device to automatically adjust its measurement and correction strategies, improving overall measurement precision without requiring permanently complex hardware for all operating conditions.

The patent employs feedback control where the sensor unit continuously monitors liquid amount and provides signals to the control unit. Based on this feedback, the system automatically switches between operational modes to correct detection errors or noise, thereby improving reliability through a relatively simple feedback loop rather than complex predictive algorithms.

The device performs self-diagnosis and self-correction by automatically detecting when measurement errors or noise occur and switching to correction modes without external intervention. This self-service capability improves reliability while keeping the control system simple, as the device manages its own error correction without requiring complex external monitoring or manual calibration.