Injection system includes an injector head that is configured to control delivery of a designated fluid to a patient. The injector head includes a syringe interface along an active side of the injector head. The syringe interface has a receiving cavity that is configured to receive a syringe barrel. The injector head also includes an internal sensor. A magnetic switch has an external magnet outside of the injector head. The external magnet is operable to modify a magnetic field experienced by the internal sensor to activate the internal sensor.
