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As with inductive proximity sensors it is possible to

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Unformatted text preview: pacitor changes. With capacitive proximity sensors, an RC resonant circuit is tuned in such way that a sensor in the unactuated state produces a stray field in front of the active surface. Only if an object enters into this zone, is it possible for the RC-oscillator to respond. The change in capacitance leads to this response. The capacitance change depends on the following factors: • Distance and position of the object in front of the electrode • Dielectric constant of the object • Dimensions of the object If a non-conductive object is introduced into the active zone, then capacitance increases with the dielectric constant εr of the material and vice versa in proportion with the distance from the disc-shaped capacitor electrode. The greatest switching distance is achieved with either a water surface or with earthed, electrically conductive materials. The smaller the relative dielectric constant of a nonconductive material, the smaller the switching distance. As with inductive proximity sensors, it is possible to detect moving or stati...
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