1
Michael F Gard, Jian Jin, John C Wisehart: Electronic compass. The Charles Machine Works, Sidley & Austin, December 15, 1998: US05850624 (134 worldwide citation)

An electronic compass (10) for use in a boring tool (12) which will provide an orientation of the boring tool relative to the earth's magnetic field. In addition, a more straightforward left or right deviation from an initial bearing can be determined. The invention can correct for pitch angle and r ...


2
John C Wisehart, Austin L Widener, Jian Jin: Apparatus and method for determining boring direction when boring underground. The Charles Machine Works, McKinney & Stringer P C, March 9, 1999: US05880680 (25 worldwide citation)

A guidance module for an underground horizontal boring assembly. The module determines the pitch angle of the boring tool independent of roll using a single accelerometer sensor. The accelerometer sensor has a single sensitive axis which is aligned parallel to, and preferably coaxial with, the longi ...


3
John W Bieberdorf, John C Wisehart, Greg W Draper: Roll independent variable inductance inclinometer. The Charles Machine Works, Sidley & Austin, December 30, 1997: US05703484 (14 worldwide citation)

The pitch sensor of the invention includes a sealed container filled about half full with a magnetic liquid. A pair of coils are wound around the container and produce inductances corresponding to the amount of magnetic liquid disposed within the opening of the coils. As the angle of inclination of ...