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.

Abstract: A set of radial springs to bias the sensor arms of an inline pipeline inspection tool radially outward towards the pipe wall. The springs are resilient clips typically made of metal which bias adjacent sensor arms away from one another and radially outward. There are two sets of springs, a forward set and a rearward set which operate independent of each other. Each set of springs operates on a plane which is perpendicular to the axis of the body of the tool and perpendicular to the planes upon which the sensor arms extend.