The present invention relates to a device for measuring a physiological parameter of a human limb such as peripheral capillary oxygen saturation. The device comprises a body comprising a first body part and a second body part, which are movable relative to each other to define an opening with an adjustable size for receiving the limb therein, and a physiological sensor for interacting with the limb received in the opening, the sensor being attached to the body, wherein the first and second body parts are slidable or twistable relative to each other while at least partially engaging or intersecting each other, or wherein the first and second body parts are configured to form a clip having an L-shaped end section for at least partially enclosing the limb received in the opening, in order to adjust the size of the opening.