A detection device for detecting a diameter and/or composition of a welding wire and/or welding electrode for a welding device, includes an oscillating circuit, which has a coil through which the welding wire and/or welding electrode can be passed. The device further include an evaluation unit connected to the oscillating circuit for determining at least one first oscillating circuit parameter which is characteristic of an attenuation of an oscillation signal occurring in the oscillating circuit, and at least one second oscillating circuit parameter which is characteristic of a signal frequency f of the oscillation signal occurring in the oscillating circuit. The evaluation unit detects the diameter and/or composition of the welding wire passed through the coil of the oscillating circuit and/or of the welding electrode using the determined oscillating circuit parameters.