Development of a Flowmeter for Sub Micro Liter per Second Order Unsteady Flow Rate Based on the Pressure Difference in a Capillary

Abstract

In order to measure unsteady flow rate of the order of less than 1μl/sec, a new flowmeter consisting of a capillary and a pressure gauge has been developed. When a target flow passes through the capillary, the measured pressure loss in the capillary gives the flow rate according to the Hagen-Poiseuille equation, which indicates the flow rate is proportional to the pressure loss. Investigating prototype flowmeter characteristics in the case of steady flow of water, we confirmed that the flow rate given by the Hagen-Poiseuille equation derived from the measured pressure loss accords with the flow rate estimated by the gravimetric technique. The accuracy is within ± 1 %. When the flow rate decreases gradually, the measured flow rate accords with the theoretical value at each moment. This flow meter enables to measure time varying flow rate. In the case that the flow rate abruptly changes, the measured pressure has a time delay because of the property of the pressure gauge used in this study. Compensation for this time delay is demonstrated.

Keywords

• flowmeter
• flow measurements
• unsteady flow
• capillary
• microfluidics
• micro pumps
• micromechanics