PERFORMANCE OF AN ANISOTROPIC MAGNETO-RESISTIVE ELECTRICAL ENERGY METER

Abstract

ABSTRACT Electro-mechanical energy meters provide an excellent combination of simplicity and reliability and have been used for over a hundred years. They only indicate units consumed and need for additional functionalities made the transition to solid-state electrical energy meters a necessity. Most energy meters use traditional current sensors which have shortcomings like thermal drift, limitation of frequency range, cost, size and lack of electrical isolation. In this research an Anisotropic Magneto-Resistive (AMR) current sensor which overcomes the above disadvantages were tested and found to have a linear characteristic suitable for electrical energy metering. A digital electrical energy meter based on the AMR current sensor was designed using Proteus 8 Professional software, basic electronic components and an Arduino micro microcontroller which sampled and processed supply voltage and current signals through a C-code program. The meter displayed accurate output results of supply voltage, current, power factor (pf), „real-time‟ power consumption and cumulative electrical energy (kWh) on a Liquid Crystal Display (LCD). Test-runs lasting 5 minutes were conducted and repeated on electrical loads using the developed AMR meter, Powertek and laboratory multimeters. Analysis of variance was performed on recorded data using Statistical Analysis of Systems (SAS). Means of currents, voltages and pf measured on different meters including the AMR meter were found not to be significantly different at α = 0.05. In one of the test runs, analysis of variance on data from four energy meters gave electrical energy means of 0.1197a, 0.1233a, 0.1233a and 0.1333a. Since the means were followed by the same letters, it implied that the means were not significantly different at α = 0.05 and the performances of the energy meters were therefore similar. The results showed that the AMR meter performed competitively against common domestic electrical energy meters and also displayed more useful information. Although in the performance analysis the error bars overlapped, further study needs to be carried out to investigate on how the errors could be reduced at low current loads.