Patent ID: 9592345
Date: 2017-03-14
CPC Classifications: A61M,G01F,G01S

Claim:
1. A drug delivery device with a container defining a cavity for a drug and a stopper for proximally delimiting the cavity and displacing the drug from the cavity, the drug delivery device further comprising an arrangement for determining a position (x) of the stopper relative to the container, the arrangement comprising an acoustic source configured to emit an acoustic signal and an acoustic sensor configured to detect an acoustic signal, a processing unit for controlling the acoustic source and processing the detected acoustic signal for determining characteristics of the acoustic signal correlated with the position (x) of the stopper, wherein the acoustic source is aligned to emit the acoustic signal into a resonance volume, which is defined in one spatial dimension by the position of the stopper, wherein the processing unit is configured to vary the frequency (f) of the emitted acoustic signal within a pre-determined frequency range, wherein the processing unit is configured to detect a harmonic (f 1 (x), f 2 (x), f 3 (x), f 4 (x)) of a resonance frequency f k characteristic for the resonance volume related to the position (x).