Self-Aligning and Self-Calibrating Capacitive Sensor System for Displacement Measurement in Inaccessible Industrial Environments

Self-Aligning and Self-Calibrating Capacitive Sensor System for Displacement Measurement in Inaccessible Industrial Environments

van de Ven, Oscar S. (Ultimaker)
Vogel, J.G. (TU Delft Electronic Instrumentation)
Xia, Sha (NXP Semiconductors)
Spronck, J.W. (TU Delft Mechatronic Systems Design)
Nihtianova, S. (TU Delft Electronic Instrumentation)

2018

High-precision positioning often requires high speed and high resolution displacement measurements in order to compensate for the small vibrations of critical components. The displacement sensor must be precise and stable over a long period of time to avoid expensive recalibration. This requires tight mounting tolerances, which are especially difficult to meet in inaccessible environments. The proposed sensor system is based on a capacitive sensor and consists of three subsystems: 1) a mechanical ``zoom-in'' system that performs self-alignment of the capacitive sensor electrode in order to reduce the mounting tolerances of the sensor; 2) a real-time capacitance-to-digital converter that employs an internal reference and electrical zoom-in technique to effectively reduce the dynamic range of the measured capacitance, thus improving the power efficiency; and 3) a self-calibration circuit that periodically calibrates the internal references to eliminate their drift. In previous publications, the three subsystems have been introduced. This paper shows how the different subsystems can be integrated to achieve optimal performance and presents new repeatability and stability measurement results. The overall system demonstrates a displacement measurement resolution of 65 pm (in terms of capacitance 65 aF) for a measurement time of 20 μs. Furthermore, the thermal drift of the sensor is within 6 ppm/K, owing to the self-calibration circuit. In measurement mode, the system consumes less than 16 mW.

Capacitive sensor
high-resolution capacitive-sensor interface
inaccessible environments
self-alignment
self-calibration
thermal actuator
thermal stability

http://resolver.tudelft.nl/uuid:c60bf7a2-d920-4858-8224-275e1fd819c6

https://doi.org/10.1109/TIM.2017.2764333

0018-9456

IEEE Transactions on Instrumentation and Measurement, 67 (2), 350-358

Accepted Author Manuscript

Institutional Repository

journal article

© 2018 Oscar S. van de Ven, J.G. Vogel, Sha Xia, J.W. Spronck, S. Nihtianova