An injection device comprising: a housing arranged to contain a liquid medicament or a medicament cartridge； an electrical coil arranged at the housing； a removable cap arranged to be removably engaged with an end of the housing； and a magnet arranged within the removable cap； wherein when the removable cap is disengaged from the housing, the magnet moves with respect to the electrical coil such that electrical voltage is induced in the electrical coil and a current is generated.一種注射裝置，包括：殼體，該殼體佈置成容納液體藥劑或者藥劑藥筒；電線圈，該電線圈佈置在殼體上；可移除蓋，該可移除蓋佈置成與殼體的端部以可移除方式接合；磁體，該磁體佈置在該可移除蓋內；其中，當可移除蓋從殼體脫離時，磁體相對於電線圈移動，使得在電線圈中感應出電壓並產生電流。
