Accuracy of the PRO gauge starts with its exclusive parabolic funnel that traps wind driven rain, so it won't splash out. Rain is funnelled into a precision drop forming tube, much like those you'd see in a hospital IV bottle. Each uniform drop coming out of the tube is equivalent to exactly 0.001 inches of rain. Each uniform drop falling from the tube is detected by four gold plated sensing electrodes that signal an electronic counting circuit. After each ten drops this circuit sends a signal to the Ultimeter keyboard indicating that another hundredth inch of rain has fallen.