A measurement device has already been disclosed by German Patent Publication 195 24 634 A1, which includes a plate-shaped sensor element with a dielectric membrane that is inserted into a recess of a sensor support. The sensor element is made of a semiconductor material, e.g. silicon, and is manufactured in a micromechanical construction. The membrane is comprised of a dielectric material, for example silicon nitride or silicon oxide. A measurement resistor and a heating resistor are disposed on the dielectric membrane, which are to a large extent thermally insulated from a silicon frame that encompasses the membrane due to the thin embodiment of the membrane and the low heat conductivity of the dielectric membrane. Between the dielectric membrane and the sensor support, there is a hollow space in the plate-shaped sensor element, which extends from a bottom face adjoining the sensor support to the dielectric membrane and is manufactured, for example, by means of an etching process. The sensor element is fixed in the recess of the sensor support by means of a glue. Since the relatively thin membrane must be protected from excess pressure peaks, a ventilation of the hollow space provided underneath the membrane cannot be omitted. The ventilation of the recess in the measurement sensor or the rear of the membrane, however, must take place so that a flow of the medium is kept away from the rear of the membrane in order to prevent the rear flow from contributing to the measurement signal. In order to prevent the penetration of glue into the hollow space adjoining the membrane, the gluing region does not extend over the entire sensor element, but the sensor element is glued into the recess of the sensor support on only half of its surface and the region of the sensor element which has the electric membrane is disposed freely in the recess. In order to prevent underflow of the membrane, i.e. a flow of the medium to the hollow space embodied underneath the membrane, or to at least counteract this, a flow conduit is provided, which is embodied in the sensor support as a channel-shaped recess and extends around the sensor element. At the same time, the provision is made that the recess embodied in the sensor support is matched to the dimensions of the sensor element so that only a small gap respectively remains between the lateral boundary of the sensor element and the lateral boundary of the recess in the sensor support, which permits only a throttled flow of the medium to the hollow space disposed underneath the dielectric membrane.
However, it is disadvantageous in this embodiment that the sensor element must be aligned with high precision in regard to the recess of the sensor support during mounting in order to produce the extremely narrow gap. But this task cannot always be reliably fulfilled for tolerance reasons and due to manufacturing variations so that not insignificant losses in efficiency occur during manufacture.
A measurement device can be inferred from German Patent Publication 42 19 454 A1, in which a sensor element with a dielectric membrane is inserted into the recess of a cooling body. The cooling body has a ventilation bore between the cooling ribs in order to assure the ventilation of the rear of the membrane.