The present invention provides a flow meter (100) for a pipe or open channel (102). The flow meter (100) has a longitudinal member (114) adapted to be inserted into the pipe or open channel (102) but free of any internal wall of pipe or open channel (102). The longitudinal member (114) has a plurality of pairs of acoustic transducers (120, 122) located there around with each pair of acoustic transducers (120, 122) having a transmitting transducer and a receiving transducer. The transmitting transducer sends an acoustic signal to the internal wall of pipe or open channel (102) and the receiving transducer receives the reflected acoustic signal.