Flow meter comprising: - a housing comprised of an inlet section and an outlet section, as well as a widened section located in between and comprised of a guide portion connecting to the inlet section and a measuring portion connecting to the guide portion and the outlet section; - helical guide blades located in the guide portion and connected to the housing; - a core present within the guide blades; - a measuring chamber located within the measuring portion, which chamber is bounded on an outside by the measuring portion of the housing, is bounded on an inlet side by the guide blades, is bounded on a running side located opposite to the inlet side by an end face of the outlet section oriented to the measuring chamber, and is bounded on an inside by an end of the core; - a measuring ball present in the measuring chamber; and - an opening present between the core-end bounding on the measuring chamber and the outlet-section-end-face oriented to the measuring chamber, wherein between the end of the core bounding on the measuring chamber and the end face of the outlet section oriented to the measuring chamber no wall portions are present, and the distance between the outside edge of the core end bounding on the measuring chamber and the inside edge of the end face of the outlet section oriented to the measuring chamber is smaller than the diameter of the measuring ball, and wherein the guide blades are each provided with an inlet end bounding on the inlet section and an outlet end bounding on the measuring chamber, wherein the outlet end of the guide blades is provided with a recess that has an arched bounding wall, where the maximum distance between the end face of the outlet section oriented to the measuring chamber and this arched bounding wall is larger than the diameter of the measuring ball, and the minimum distance between the end face of the outlet section oriented to the measuring chamber and this arched bounding wall is smaller than the diameter of the measuring ball. - a housing comprised of an inlet section and an outlet section, as well as a widened section located in between and comprised of a guide portion connecting to the inlet section and a measuring portion connecting to the guide portion and the outlet section; - helical guide blades located in the guide portion and connected to the housing; - a core present within the guide blades; - a measuring chamber located within the measuring portion, which chamber is bounded on an outside by the measuring portion of the housing, is bounded on an inlet side by the guide blades, is bounded on a running side located opposite to the inlet side by an end face of the outlet section oriented to the measuring chamber, and is bounded on an inside by an end of the core; - a measuring ball present in the measuring chamber; and - an opening present between the core-end bounding on the measuring chamber and the outlet-section-end-face oriented to the measuring chamber, wherein between the end of the core bounding on the measuring chamber and the end face of the outlet section oriented to the measuring chamber no wall portions are present, and the distance between the outside edge of the core end bounding on the measuring chamber and the inside edge of the end face of the outlet section oriented to the measuring chamber is smaller than the diameter of the measuring ball, and wherein the guide blades are each provided with an inlet end bounding on the inlet section and an outlet end bounding on the measuring chamber, wherein the outlet end of the guide blades is provided with a recess that has an arched bounding wall, where the maximum distance between the end face of the outlet section oriented to the measuring chamber and this arched bounding wall is larger than the diameter of the measuring ball, and the minimum distance between the end face of the outlet section oriented to the measuring chamber and this arched bounding wall is smaller than the diameter of the measuring ball.