Accuracy of Low-cost Flow Meters for Stemflow Observation Including Handmade Tipping Buckets Flow Meter

Abstract

 This study examined the accuracy of low-cost flow meters used for field observations. We specifically examined handmade tipping buckets flow meters, volumetric flow meters, and tap water meters. For inflow rates lower than one tip per 2 s, laboratory tests demonstrated that handmade tipping buckets flow meters have the same calibration line among inflow flux and one tipping quantity as commercial ones. Calibration curve characteristics of tipping buckets flow meters were estimated from the tipping time and storage volume when tipping. Stemflow observation measurements in the field with handmade tipping buckets meters were within 5% error. Volumetric flow meters and tap water meters must be used to add some flow current exchange systems because they are unable to detect water flow at lower flux, such as when they are dropping. Moreover, tap water meters require 2 m water height pressure at the meter exit. Volumetric flow meters have shown large error in field experiments because they are vulnerable to fluid impurities. Some measures must therefore be used to remove impurities. We were able to judge comprehensively that handmade tipping buckets flow meters are superior in many respects as low-cost flow meters for field observations.