Correcting capacitive displacement measurements in metrology applications with cylindrical artifacts

Philip T. Smith, R. Ryan Vallance, Eric Russell Marsh

    Research output: Contribution to journalArticlepeer-review

    44 Scopus citations


    Metrology applications commonly require non-contact, capacitive sensors for displacement measurements due to their nanometer resolution. In some metrology applications, for example, the measurement of roundness and spindle error motion, the displacements of stationary and rotating cylindrical artifacts are measured. Error from using a conventionally calibrated sensor with a non-flat (e.g., cylindrical) target is typically neglected, but these errors cannot be ignored for nanometer-level accuracy. The capacitance between a sensor and a cylindrical target is less than that of a sensor with a flat target, which causes four effects. As the diameter of the target shrinks, the sensitivity of the sensor increases, the sensing range decreases, the sensing range shifts towards the target, and the nonlinearity increases. These errors can be greatly reduced by either calibrating sensors with the correct target surface or by determining corrections for post-processing data. This paper quantifies and experimentally verifies these errors for a commonly used sensor, and a simulation of a nanometer-level measurement of out-of-roundness and spindle error motion demonstrates that measurement accuracy is improved with corrected sensitivities.

    Original languageEnglish (US)
    Pages (from-to)324-335
    Number of pages12
    JournalPrecision Engineering
    Issue number3
    StatePublished - Jul 1 2005

    All Science Journal Classification (ASJC) codes

    • General Engineering


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