Abstract: Apparatus for measuring the pressure of a fluid includes a first pressure transmission element in form of a membrane in contact with a pressure sensor, and a second pressure transmission element in form of a membrane which is acted upon by a fluid whose pressure is to be determined. The first membrane has a peripheral area which is pressed against the second membrane in such a manner that the space between the first and second membranes is sealed off from outside and is of a size as small as possible. Both membranes thus move in synchronism in dependence of the fluid pressure so that positive as well as negative pressures can be measured.