Fuel injector and method for operating a fuel injector

A fluid injector is specified. The fluid injector has a longitudinal axis (L) and comprises a valve body (6), a valve needle (12), being received in the valve body (6), being axially moveable and being operable to prevent a fluid injection in a closing position and to permit the fluid injection in further positions, an armature (14) being mechanically coupled to the valve needle (12) so that it is operable to displace the valve needle (12) away from the closing position, and a solenoid assembly (30) comprising at least a first and second coil (34, 36) and being operable to magnetically actuate the armature (14) via an electrical signal (I 1 ). A method for operating the fluid injector comprises applying the electrical signal (I 1 ) to the first coil (34) to generate a primary magnetic field to move the armature (14) for displacing the valve needle (12) away from the closing position, evaluating a voltage (U 1 ) across terminals of the first coil (34), and controlling the second coil (36) with a further electrical signal (I 2 ) to saturate a magnetic field in a portion of the valve body (6) which is located between the armature (14) and the solenoid assembly (30) during evaluating the voltage (U 1 ).