a significantly greater distance from one another than when use is made of contactless web supports if fixed shafts or the like are used a very high speed will be required in order to form an air cushion between the web and the shaft and therefore there will be no contactless deflection at low speeds pneumatic cylinders forming part of application devices 7 u2014 one for each measurement body 6 u2014 determine the pushing force of the measurement bodies by the application of different air pressures to the respective plus and minus chambers the pressure of the minus chamber can be used for example to compensate for the weight of the measurement body 6 the air pressure in the pneumatic cylinders which determines the application force of the measuring bodies against the web is entirely separate from the air pressure which the fluid supply devices apply to the web and produce the fluid cushion the housing for the pneumatic cylinders is securely attached together with one of the web supports 3 the piston rods of the cylinders are movably arranged together with the central parts of the device 1 u2014 measurement bodies 6 fluid supply devices 2 and sensing bodies for the measurement sensor u2014 in such a way as to permit the variable tension.