A device for measuring at least one parameter of a medium flowing in a line, particularly the intake-air volume of an internal combustion engine. Liquid particles contained in the line act upon a measuring element and influence a characteristic curve of the measuring element which is used to determine parameters of the flowing medium. The characteristic curve of the measuring element can be changed disadvantageously by solid-matter particles. In order to reduce the action of solid-matter particles on the measuring element, a protective grating is proposed in which side walls of channels of the protective grating form various angles of intersection with the flow direction. Solid-matter particles are thereby diverted into a path of motion around the measuring element.