Validation of a Novel Electromagnetically Operated Free Flow Liquid Dispensing System

Abstract

Repeat dispensing of liquids is a common requirement in many industries, often performed using automated machinery. These instruments often use complex mechanisms requiring expensive parts that may not be readily available. In resource-constrained regions there is a need for a simple device capable of reproducibly dispensing a controlled volume of fluid accurately. We evaluated the performance of a semi-automated liquid dispenser made from readily available parts that utilizes a programmable timer to trigger the activity of an electromagnetic valve, which allows delivery of liquid from a storage tank to the delivery nozzle via a flexible tube. The device was programmed to deliver a wide range of volumes and a gravimetric analysis of dispensed liquid was performed. The dispensed liquid maintained a linear relationship with the delivery time within the tested delivery range of 0.05 gram to 1.8 gram. It demonstrated high accuracy (>95%) and precision (coefficient of variation of <10%) for dispensing quantities more than 0.2 gram. However, the accuracy and precision suffered significantly below 0.2 gram. By changing nozzle diameters, we found a similar linear relationship between time and dispensed water weight for all tested nozzle sizes. By using a wide range of nozzle diameters, we could increase the range of delivery weight from 0.03 gram to 28.4 gram, with a very similar precision. This simple instrument is a user friendly, cost-effective, resource-efficient and reliable alternative for repeatedly dispensing a wide variety of liquids with various industrial applications, within a given volume range.