A device for detecting a conduit and for determining at least one characteristic of its content includes a seat for housing at least a portion of the conduit. The seat has first and second zones which are opposite each other with respect to a recess intended to receive the conduit. A light emitter is arranged in the first zone, and has a preferential emission direction oriented towards the recess. A receptor sensitive to the light emitted by the emitter also has a preferential reception direction oriented towards the recess. A first deflector deflects light in the direction of the first zone when a conduit containing a substantially transparent liquid is engaged in the seat. A second deflector deflects in the direction of the second zone at least part of the light deflected by the first deflector so that, when a conduit containing a substantially transparent liquid is engaged in the seat, at least part of the light emitted by the emitter reaches the receptor after having passed through the conduit at least twice obliquely with respect to a longitudinal axis of the recess. The components are arranged so that in the absence of a conduit in the seat, at least part of light from the emitter reaches the receptor after a single deflection.