The Ultraguard (U.S. Patent No. 6,147,851) was developed for Linear Measurements, (which owns NLS, Inc.) in San Diego, California, USA by Valid Measurements. Again, the need was to eliminate the measurement errors that arise when lead wires pass through severe environments as they connect transducers to their signal conditioning. The classical driven guard technique applies only to electronic circuit regions that contain a single potential. In meeting this need, a more general electrical guarding theory was developed that results in another fundamental electrical measurement circuit topology.

The Ultraguard principle uses a driven outer guard to effectively guard regions within an inner guard that contains various potential gradients and noise sources. The gradient-guard configuration contains charges within an inner guard and the charge-channel configuration assures that the current entering a conductor at one end will all exit the conductor at its other end even when the conductor and its guards are imbedded in poor insulation resistance to ground. The ultraguard can significantly reduce the externally-observable effects of noise potentials within the guarded region which may arise from tribo-electric effects, radiation exposure, electromechanical  inputs and other noise sources. The new Ultraguard topology complements the Anderson loop by assuring that all excitation current actually reaches its destination in spite of severe insulation leakage as well as preserving signals from noise that may arise within connecting cables.