Abstract: The present invention provides a way to increase the density of Hall effect sensors on a MFL inline inspection tool mounting the sensors on a first circuit board which overlies a second circuit board. Op amps for the sensors which condition and filter the analog signal from the sensors are mounted on the first circuit board. Microprocessors mounted on the second circuit board receive the analog signal from the op amp and translate it into a digital signal. Use of the stacked circuit boards doubles the amount of area to mount the sensors and their op amps and microprocessors while maintaining the same footprint. This results in being able to increase the number of Hall effect sensors in that footprint area. In other embodiments the number of layers of circuit boards may be increased beyond two.