An example injector includes a rotary knob for selecting a function and setting a dosing quantity for an injection, a button located on an end of the rotary knob for initiating the injection, an electric motor, an encoder for evaluating output rotary motion of the motor, and a processor that converts the dosing quantity into a number of encoder pulses and controls operation of the motor based on the number of encoder pulses when dosage is triggered. The injector also includes a transmission coupled to the electric motor to convert a speed of the motor, a threaded spindle coupled to the transmission that moves linearly based on the output rotary motion of the motor at the speed as converted by the transmission, and a punch connected to an end of the threaded spindle. The linear movement of the spindle causes the punch to release medicament.本發明揭示一種實例性注射器，其包含：一旋鈕，其用於選擇一功能及設定用於一注射之一加藥量；一按鈕，其定位於該旋鈕之一端上以用於起始該注射；一電馬達；一編碼器，其用於評估該馬達之輸出旋轉運動；及一處理器，其將該加藥量轉換成數個編碼器脈衝且在觸發加藥時基於編碼器脈衝之數目控制該馬達之操作。該注射器亦包含：一變速箱，其耦合至該電馬達以轉換該馬達之一速度；一螺紋心軸，其耦合至該變速箱以按該變速箱轉換之該速度基於該馬達之該輸出旋轉運動線性移動；及一衝頭，其連接至該螺紋心軸之一端。該心軸之該線性移動引起該衝頭釋放藥劑。
