Magnetic inclination measurement and signal transmission system for trench wall constructions

A NdFeB permanent magnet pendulum varies the output voltage of a semiconductor Hall-effect potentiometer. The angle dependent dc-voltage is converted into a signal of variable frequency (2-15 kHz). The angle sensors, the electronic circuits, and batteries are mounted in water-proof (20 bar) and shock protected (100 g) cases on the gripper. It is operated by two steel cables which are used for the signal transmission by enclosing ring-core transformers of high initial permeability. The received angular information is decoded by a microprocessor and displayed together with the excavation depth on a screen in the operation cabin of the excavator. The measurement system provides an angular resolution of 5.10/sup -3/ degrees and an absolute accuracy of 7.10/sup -3/ degrees at /spl plusmn/2 degrees total range.<>