A measuring device for determining the oxygen content in gases is described. The measuring device is disposed between two magnets that are positioned at a distance from one another. The measuring device is equipped with a sensor that is held rotatably within a frame. The sensor has two parallelepipedic bodies that are both made hollow or solid and are connected to one another via a web-shaped structural element. The web-shaped structural element is fastened to the frame via at least one holding element, so that the sensor can be rotated about its center of gravity. The amount of rotation is dependent on the quantity of oxygen that is concentrated between the two magnets. A current can be conducted through a conductor track led on the surface of the sensor and generates a correspondingly high restoring force by which the sensor is brought into the position of rest again.