Wattmeter comprising a hall sensor and an A/D converter

Wattmeter including a Hall sensor circuit and an A/D converter, said Hall sensor including a plurality of Hall elements for producing a plurality of sensor voltages, said A/D converter comprising an impulse-width delta modulator, an impulse shaper, first and second frequency dividers with division ratios N and M, respectively, said frequency dividers connected to said impulse shaper, a compensation circuit for generating a compensation voltage, an adding circuit which receives said plurality of sensor voltages, a reference voltage, and said compensation voltage, a source for producing said reference voltage, said adding circuit producing an output signal fed to the input of said modulator, and a clock generator for generating clock pulse and first and second output signals,

• said modulator generating an output signal fed to the input of a counter forming part of the compensation circuit and also fed to the input of the impulse shaper,
• an inverted output of the modulator being connected to the input of the first frequency divider, the inverted output and a non-inverted output of the modulator being connected to first and second sets, respectively, of control terminals of adding circuit control switches in the adding circuit,
• and the sensor circuit includes a plurality of sensor switches being interconnected to a bridge with the sensor elements in a diagonal between two output terminals of each of said sensor elements, feeding terminals of said sensor elements being parallel-connected and a mains phase terminal being connected to a first input terminal of the bridge through a resistor, whereas a mains zero terminal of said sensor circuit being mass connected.