The invention relates to a method for producing gear plates for a continuously variable gearbox wherein at least two gear plates with the transmission surfaces thereof are arranged in an opposite mauler. The transmission frequency and the angle of incidence onto the pipe can be selected to suppress frequency dependence of a measured value due to Lamb wave and allow the flow velocity or flow rate of fluid to be measured with a greater accuracy. The method further includes storing the plurality of encrypted query data packets in a memory. The inner conduit has a second fluid inlet distal from the first fluid outlet and a second fluid outlet proximate the first fluid outlet.