Abstract: A capacitive position sensing system has a pickup electrode, a shield electrode partially enclosing the pickup electrode, and an essentially grounded relatively movable target near the pickup electrodes; a capacitance-to-digital converter, and switching means for connecting each electrode in turn to the converter input or to ground. A capacitive position sensing method in the system includes measuring a first capacitance C1 of at least one pickup electrode set with the shield electrode set grounded, measuring a second capacitance C2 of at least one shield electrode set with the pickup electrode set grounded, and measuring a third capacitance C3 of the pickup electrode set and the shield electrode set connected together; and calculating a first result indicating a position of a target using the first capacitance C1, the second capacitance C2 and the third capacitance C3.

Abstract: Two similar incremental sensors, one with 2N+1 spatial periods or pitches over a range of 2R, or N+0.5 pitches over a range of R, and the other with 2N?1 pitches over the range of 2R, or N?0.5 pitches over a range of R, measure a common position along an axis x. Both sensors consist of a scale having spatially periodic features that define the above pitches, and a reading head. An exact absolute position over the maximum range of 2R can be computed from outputs of the two sensors with a resolution about twice that of one sensor. For a reduced absolute range of less than R, computing the correct absolute position becomes simpler and more tolerant of sensor linearity. A preferred embodiment is a compact and linear absolute gauge combining two inductive incremental sensors, replacing current analog LVDT or half-bridge inductive gauges.

Abstract: A pulsed coil drive for a sampled inductive transducer has at least one drive coil connected in a series circuit with a capacitor having a first terminal connected to the negative terminal of a voltage source. The series circuit is normally open during the intervals between pulses. Sampling occurs once per pulse. Each pulse's sampling interval is preceded by a pre-sampling interval and followed by a post-sampling interval. The supply voltage that is applied across the series circuit during both the pre- and post-sampling intervals is applied by switching a first terminal of the coil's free terminal to the voltage source's positive terminal through a p-channel MOSFET. During the sampling interval, the series circuit is shorted by switching the coil's free terminal to the voltage source's negative terminal through an n-channel MOSFET.

Abstract: An inductive position sensor has a spatially periodic scale with a series of conducting or permeable features of pitch T and a reading head with drive windings and sense windings, facing the scale with a spatial period 2T along the scale. The windings are each divided in two identical winding elements,having the same relative location within two identical winding element patterns having a center-to-center distance along the scale of NT+T/2, N being an integer, and connected so that the winding element polarities in each winding are either opposed for drive windings and the same for sense windings or the same for drive windings and opposed for sense windings. Thereby, direct couplings in both patterns cancel each other, while the spatially periodic signals coupled via the scale reinforce each other.

Abstract: The pulsed coil drive for a sampled inductive transducer has at least one of its drive coils forming a series circuit with a capacitor whose free terminal is connected to the negative terminal of a voltage source. This series circuit is normally open, i.e. has no current during the intervals between pulses. Sampling occurs once per pulse and needs a minimum time for the sampled signal to settle to the required accuracy. Each pulse's sampling interval is preceded by a pre-sampling interval and followed by a post-sampling interval. The supply voltage is applied across the series circuit during both the pre- and post-sampling intervals by switching the coil's free terminal to the voltage source's positive terminal through a p-channel mosfet. During the sampling interval, the series circuit is shorted by switching the coil's free terminal to the voltage source's negative terminal through an n-channel mosfet.

Abstract: An inductive position sensor has a spatially periodic scale with a series of conducting or permeable features of pitch T and a reading head with drive windings and sense windings, facing the scale with a spatial period 2T along the scale. The windings are each divided in two identical winding elements having the same relative location within two identical winding element patterns having a center-to-center distance along the scale of NT+T/2, N being an integer, and connected so that the winding element polarities in each winding are either opposed for drive windings and the same for sense windings or the same for drive windings and opposed for sense windings. Thereby, direct couplings in both patterns cancel each other, while the spatially periodic signals coupled via the scale reinforce each other.