An apparatus for measuring a parameter of a fluid flowing within a pipe includes a sensing device having a sensor for sensing an unsteady pressure of the fluid flow. The sensing device generates sensor data responsive to the parameter. A processing device, which communicates with the sensing device, receives and processes the sensor data to generate meter data. The apparatus includes a digital interface, which communicates with the processing device, that is configured to associate with a portable external digital storage device for transferring information between the apparatus and the portable external digital storage device.