University of Michigan

Other

Steven A Rogacki

Thomas Zurbuchen

Robb S Gillespie

A compact instrument package consisting of a rotating sensor and supporting signal-processing electronics is capable of measuring two-dimensional electric-field vectors, ranging from DC to an arbitrary upper AC frequency not limited by the rotation rate, with highly improved accuracy and sensitivity when compared with previous art. In addition, contrary to previous art, the sensor can measure the electric field gradient at its location. This is achieved by the use of a combination of quadrature modulation and phase-sensitive quadrature demodulation digital signal processing in a generic rotating electric-field sensor. Ground isolated versions of the instrument can be used singly or in arrays when precise measurements of the electric fields are necessary. Either grounded or isolated versions of the instrument can operate continuously without the need for internal batteries, making it extremely attractive for a wide-range of industrial and space applications. Operational modes have been developed to distinguish the effects of ion currents and charged particles impacting the sensor from the local ambient electric field. Moreover, particular versions of the instrument can be operated in corrosive environments and conducting fluids.

Rotating electric-field sensor

Various techniques are described for high resolution time measurement using a programmable device, such as a field programmable gate array (FPGA). The timing may be triggered by any event, depending on the applications of use. Once triggering has occurred, a START pulse begins propagating through the FPGA. The pulse is able to propagate through the FPGA in a staggered manner traversing multiple FPGA columns to maximize the amount of time delay that may be achieved while minimizing the overall array size, and thus minimizing the resource utilization, of the FPGA. The FPGA timing delay is calibrated by measuring for the linear and non-linear differences in delay time of each unit circuit forming the staggered delay line path for the timing circuit. The FPGA is able to achieve nanosecond and sub-nanosecond time resolutions.

High resolution time measurement in a FPGA

Various techniques are described for high resolution time measurement using a programmable device, such as an FPGA. The timing may be triggered by any event, depending on the applications of use. Once triggering has occurred, a START pulse begins propagating through the FPGA. The pulse is able to propagate through the FPGA in a staggered manner traversing multiple FPGA columns to maximize the amount of time delay that may be achieved while minimizing the overall array size, and thus minimizing the resource utilization, of the FPGA. The FPGA timing delay is calibrated by measuring for the linear and non-linear differences in delay time of each unit circuit forming the staggered delay line path for the timing circuit. The FPGA achieves nanosecond and sub-nanosecond time resolutions and is used in applications such as various time of flight systems.

A tool tip conductivity sensor and method for determining when a tool tip of a machine contacts a workpiece. The sensor has at least two external connectors, one to the workpiece and the other to the machine. When the tool tip grazes the workpiece surface an electrical circuit is completed. The signal from the contacts is supplied to a trigger circuit, which preferably compares the signal to a DC offset. The trigger signal from the trigger circuit is supplied to a notification circuit, which provides a signal indicating contact. Preferably, the notification circuit receives the trigger signal and provides a steady &ldquo;On&rdquo; condition for an LED or activates an audible device, such as a piezoelectric transducer. The notification circuit can also provide a reference for further machining to a controller of the machine using the sensor as a contact probe.

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Chelsea, MI, United States of America

Steven A Rogacki