A flow meter arranged to measure a flow rate of a fluid flowing through a flow tube, wherein the flow meter comprises: - the flow tube, and - an ultrasonic flow meter housing, the flow meter housing comprising: - a flow meter cup, and - a lid, the flow meter cup comprising: - a first cup section comprising: - a first cup cavity arranged for accommodating: - two ultrasonic transducers (121a, 121b) for emitting and receiving ultrasonic signals, and - an electronic circuit for operating the transducers (121a, 121b), and - a second cup section, and an opening, wherein the ultrasonic flow meter housing is mounted onto the flow tube so as to allow ultrasonic signals from said transducers (121a, 121b) to pass across the fluid flowing through the flow tube, wherein the second cup section comprises a hermetically sealed electrical feedthrough, wherein the hermetically sealed electrical feedthrough is a metallic feedthrough, wherein the first cup section comprises a first cup structure comprising the first cup cavity and a first cup opening, and the second cup section comprises a second cup structure which is arranged in the first cup opening, so as to provide a first closed connection between the first cup structure and the second cup structure, wherein a first sealing means hermetically seals the first closed connection, wherein the lid is arranged in the opening of the first cup structure, so as to provide a closed connection between the first cup structure and the lid, and wherein a sealing means hermetically seals the closed connection. - the flow tube, and - an ultrasonic flow meter housing, the flow meter housing comprising: - a flow meter cup, and - a lid, - a flow meter cup, and - a lid, the flow meter cup comprising: - a first cup section comprising: - a first cup cavity arranged for accommodating: - two ultrasonic transducers (121a, 121b) for emitting and receiving ultrasonic signals, and - an electronic circuit for operating the transducers (121a, 121b), and - a second cup section, and - a first cup section comprising: - a first cup cavity arranged for accommodating: - two ultrasonic transducers (121a, 121b) for emitting and receiving ultrasonic signals, and - an electronic circuit for operating the transducers (121a, 121b), and - a first cup cavity arranged for accommodating: - two ultrasonic transducers (121a, 121b) for emitting and receiving ultrasonic signals, and - an electronic circuit for operating the transducers (121a, 121b), and - a second cup section, and an opening, wherein the ultrasonic flow meter housing is mounted onto the flow tube so as to allow ultrasonic signals from said transducers (121a, 121b) to pass across the fluid flowing through the flow tube, wherein the second cup section comprises a hermetically sealed electrical feedthrough, wherein the hermetically sealed electrical feedthrough is a metallic feedthrough, wherein the first cup section comprises a first cup structure comprising the first cup cavity and a first cup opening, and the second cup section comprises a second cup structure which is arranged in the first cup opening, so as to provide a first closed connection between the first cup structure and the second cup structure, wherein a first sealing means hermetically seals the first closed connection, wherein the lid is arranged in the opening of the first cup structure, so as to provide a closed connection between the first cup structure and the lid, and wherein a sealing means hermetically seals the closed connection.