Journal ArticleDOI
Electronic transducers for industrial measurement of low value capacitances
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TLDR
In this article, the effects of stray capacitances on the measurement system must be minimized, in order to achieve high measurement sensitivity and good signal-to-noise ratio.Abstract:
Reviews existing instrumental techniques suitable for industrial measurement of capacitance in the range 0.1-10 pF, including resonance, oscillation, charge/discharge and AC bridge methods. It shows that in order to achieve high measurement sensitivity and good signal-to-noise ratio, the effects of stray capacitances on the measurement systems must be minimised. Several intrinsically stray-immune measuring circuits are described, including an audio-frequency transformer-ratio-arm bridge and a charge/discharge measuring circuit capable of operating at frequencies up to several MHz. The active guard method and suitable guard driving techniques for reducing the effects of strays on the measurement of grounded capacitances sensors are described. Techniques for reducing the baseline drift of the capacitance measuring circuits, such as auto-balancing and auto-calibration, etc., are also discussed.read more
Citations
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Planar capacitive sensors – designs and applications
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References
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Journal ArticleDOI
Application of capacitance techniques in sensor design
TL;DR: In this paper, the basic principles of capacitance, and also clarifying some of the misconceptions about the principles of guarding, which were correctly described by Kelvin more than a century ago, are discussed and the possibilities for combining bridge circuits with simultaneous and sequential measurements of complex sensors are described.
Journal ArticleDOI
The design and some applications of sensitive capacitance micrometers
R V Jones,J C S Richards +1 more
TL;DR: In this paper, a general account of both the electrical and the mechanical aspects of the design of capacitative transducers and their associated electronic circuitry suitable for observing displacements of the order 10-2 to 10-11 mm.
Journal ArticleDOI
Phase sensitive detection as a means to recover signals buried in noise
D P Blair,P H Sydenham +1 more
TL;DR: In this article, phase sensitive detection is formalized in order that its operation can be understood and its practical use optimized, and the theory explains how narrow bandwidth amplification is achieved in order to reduce the noise content of a measurand and how the process can be considered simply as a multiplier followed by a low-pass filter.
Journal ArticleDOI
Advances in lock-in amplifiers
TL;DR: The key specification points of lock-in amplifier systems for signal recovery and signal characteristics are reviewed and it is shown how these can be improved and modified by more advanced system design.