New Accurate Wattmeter Based on Logarithmic Amplifiers

Abstract

Analog Computers can realize most of mathematical equations; these equations can be solved using difference, adder, logarithmic, anti-logarithmic, integrator, and differentiator amplifiers. The logarithmic and anti-logarithmic amplifiers are the main components of the analog computers, whereas, they can convert the multiplication and division operations to addition and subtraction ones, and they can convert the exponential functions to multiplication relationships. These amplifiers depend on the non-linearity of the relation between forward current and applied voltage of the diode. All of previous types of wattmeters, measure the consumed power of a specific load or resistor by multiplying the difference voltage of that load by the current passes through it (i.e. P=V.I). In this paper, a proposed accurate wattmeter circuit has been designed and implemented using logarithmic, anti-logarithmic, non-inverting, and difference amplifiers. The proposed circuit has been utilized for measuring the consumed power of a resistor that have any resistance value. It differs from previous conventional (analog, and digital) wattmeters due to its calculation of the consumed power for a given resistor by multiplying the voltage difference (V) across that resistor by itself once time, then the resultant value is divided by the resistance (R) value of that resistor (i.e. P=V 2 /R).