An apparatus for measuring a rate of liquid flow through a spray nozzle includes a container with an opening in a top thereof adapted to receive a liquid discharge from a spray nozzle. A level sensor comprises an electrical capacitor oriented substantially vertically in the container and configured such that as liquid rises in the container, a capacitance of the capacitor changes. A processor circuit is connected to the capacitor and is operative to measure the change in capacitance of the capacitor and convert the change in capacitance into a rate of liquid flow into the container, and a display is operative to display the rate of liquid flow. The apparatus is applicable to an agriculture or industrial application whereby an operator can periodically check the flow to determine wear or plugging of a spray nozzle.