US Patent 11660401 Drug delivery device with non-contact sensor

A drug delivery device includes a magnet assembly, a coil assembly and processing circuitry. The magnet assembly has a plurality of magnets arranged in a ring. The coil assembly has one or more coils. The magnet assembly and the coil assembly are arranged to rotate relative to each other during ejection of medicament from the drug delivery device such that a voltage signal is produced in the coil assembly when a unit of dose is ejected. The processing circuitry is arranged to: receive the voltage signal; increment a counter in response to receipt of the voltage signal; and store information indicative of the number of units of dose ejected during a medicament ejection.