Sensor for measuring a vital parameter in the ear canal of a human person or animal, comprising: a sensor element fixture, which can be positioned at least partially in the ear canal, a sensor element, which can be connected to the sensor element fixture and can be positioned at least partially in the ear canal and which comprises a light emitter and a light receiver, and a positioning element, suitable to position the sensor element fixture in the ear canal, whereby the positioning element can be connected to the sensor element fixture on at least one end, wherein the position of the sensor element in the ear canal is determined by the insertion depth of the sensor element fixture into the ear canal, wherein the positioning element exhibits a suitable form, corresponding to the anatomy of the interior face of the auricle, and is suitable to press the sensor element fixture into the interior of the ear canal in such a manner, that the sensor is held stable and a continuous measurement of the vital parameter in the ear canal is achieved, wherein the sensor element fixture is provided with suitable holes and/or cavities and/or channels that ensure that the ear canal is not completely closed or dampened, wherein the sensor element fixture comprises silicone as material, characterized by a control unit to monitor the positioning of the sensor in the ear canal and a display unit, wherein the position of the sensor element and/or of the sensor element fixture will be determined on the basis of the temporal change of the measurement signal during continuous measurement of the vital parameter, and after a change in the measurement signal by a predetermined value, the difference between the current position from the desired position will be indicated via the display unit and wherein the optimum position of the sensor can be indicated by a display unit. a sensor element fixture, which can be positioned at least partially in the ear canal, a sensor element, which can be connected to the sensor element fixture and can be positioned at least partially in the ear canal and which comprises a light emitter and a light receiver, and a positioning element, suitable to position the sensor element fixture in the ear canal, whereby the positioning element can be connected to the sensor element fixture on at least one end, wherein the position of the sensor element in the ear canal is determined by the insertion depth of the sensor element fixture into the ear canal, wherein the positioning element exhibits a suitable form, corresponding to the anatomy of the interior face of the auricle, and is suitable to press the sensor element fixture into the interior of the ear canal in such a manner, that the sensor is held stable and a continuous measurement of the vital parameter in the ear canal is achieved, wherein the sensor element fixture is provided with suitable holes and/or cavities and/or channels that ensure that the ear canal is not completely closed or dampened, wherein the sensor element fixture comprises silicone as material, characterized by a control unit to monitor the positioning of the sensor in the ear canal and a display unit, wherein the position of the sensor element and/or of the sensor element fixture will be determined on the basis of the temporal change of the measurement signal during continuous measurement of the vital parameter, and after a change in the measurement signal by a predetermined value, the difference between the current position from the desired position will be indicated via the display unit and wherein the optimum position of the sensor can be indicated by a display unit.