New Accurate Wattmeter Based on Logarithmic Amplifiers


Analog Computers can realize most of mathematical equations; theseequations can be solved using difference, adder, logarithmic, anti-logarithmic,integrator, and differentiator amplifiers. The logarithmic and anti-logarithmicamplifiers are the main components of the analog computers, whereas, they canconvert the multiplication and division operations to addition and subtractionones, and they can convert the exponential functions to multiplicationrelationships. These amplifiers depend on the non-linearity of the relationbetween forward current and applied voltage of the diode. All of previous types ofwattmeters, measure the consumed power of a specific load or resistor bymultiplying 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 beendesigned and implemented using logarithmic, anti-logarithmic, non-inverting,and difference amplifiers. The proposed circuit has been utilized for measuringthe consumed power of a resistor that have any resistance value. It differs fromprevious conventional (analog, and digital) wattmeters due to its calculation ofthe 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 bythe resistance (R) value of that resistor (i.e. P=V2/R).