A compact ultrasonic flowmeter for measuring flowrate and other fluid related data, comprising: a flow tube with a flow bore for passage of the fluid between an inlet and an outlet; a flowmeter housing associated with the flow tube; a printed circuit board arranged in the flowmeter housing and including a processor for controlling operations of the flowmeter; a meter circuit including two or more ultrasonic transducers provided on the printed circuit board and configured for operating the ultrasonic transducers to transmit and receive ultrasonic wave packets through the fluid; a display mounted on the printed circuit board and configured for displaying a measured flowrate and other fluid related data; one or more battery packs for powering flowmeter operations including at least the processor and the meter circuit and the display; wherein the processor and the ultrasonic transducers being surface mounted on a lower side of the printed circuit board and the display being mounted on ar upper side of the printed circuit board and wherein an antenna element is connected to a radio circuit via connectors provided on the printed circuit board and/or the antenna element, and where a radio communication device is mounted on the lower side of the printed circuit board and is connected to the radic circuit implemented on the printed circuit board wherein the radio communication device is configured to detect whether an electrical connection exists between the antenna element and its connectors and the radio circuit, and where a disconnection of the antenna element indicates a tampering event or other unauthorized access to the meter electronics. a flow tube with a flow bore for passage of the fluid between an inlet and an outlet; a flowmeter housing associated with the flow tube; a printed circuit board arranged in the flowmeter housing and including a processor for controlling operations of the flowmeter; a meter circuit including two or more ultrasonic transducers provided on the printed circuit board and configured for operating the ultrasonic transducers to transmit and receive ultrasonic wave packets through the fluid; a display mounted on the printed circuit board and configured for displaying a measured flowrate and other fluid related data; one or more battery packs for powering flowmeter operations including at least the processor and the meter circuit and the display; wherein the processor and the ultrasonic transducers being surface mounted on a lower side of the printed circuit board and the display being mounted on ar upper side of the printed circuit board and wherein an antenna element is connected to a radio circuit via connectors provided on the printed circuit board and/or the antenna element, and where a radio communication device is mounted on the lower side of the printed circuit board and is connected to the radic circuit implemented on the printed circuit board wherein the radio communication device is configured to detect whether an electrical connection exists between the antenna element and its connectors and the radio circuit, and where a disconnection of the antenna element indicates a tampering event or other unauthorized access to the meter electronics.