Design of a PC Based Mass Flow Indicator of an Electrical Motor Driven Water Lift Pump Using Motor Load Current as the Flow Sensing Parameter

Abstract

Mass flow rate of liquid at the outlet of a liquid lift pump is an important parameter to be measured and controlled in a process industry. In the present paper, the design of a PC based mass flow indicator of an electrical motor driven water lift pump using motor load current as the mass flow sensing parameter has been studied. The motor load current has been sensed by an opto-isolator based circuit and the output of this circuit has been displayed in a PC monitor using Labtech Note Book Pro software. A theoretical equation relating the output of opto-isolator circuit with mass flow rate has been derived and experimental study has been carried out to verify this theoretical equation, assuming the volume flow rate of water at constant room temperature to be proportional to mass flow rate. The experimental results are presented in the paper. It has been observed that the opto-isolator output and the on-line display in PC monitor both vary almost linearly with mass flow rate. Percentage deviation of the experimental results from ideal linearity and repeatability in terms of standard deviation are found to be within tolerable limit.

Keywords

• Mass flow rate
• Electric motor driven liquid lift pump
• Opto-isolator
• PC based flow indicator
• Motor load current