G wien bridge oscillators are used the following

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Unformatted text preview: he permissible voltage supply of the proximity sensor and which, depending on the time constant, fade away relatively slowly. In the case of unfamiliar power supply units, it is recommended to check the voltage switch-on behaviour by means of a storage oscilloscope. Depending on the specification given in the data sheets for proximity sensors, the supply voltage ripple must not exceed a certain limit value. 154 © Festo Didactic GmbH & Co. KG • FP 1110 11. Physical fundamentals 11.1 Fundamentals of inductive and capacitive proximity sensors Inductive and capacitive proximity sensors are based on the use of oscillators, their oscillating amplitude being affected by an approaching object. In order to generate sinusoidal oscillation, LC-oscillators (consisting of a coil and an capacitor), quartz oscillators and RC-oscillators (consisting of a resistance, a condenser and an amplifier, e.g. Wien bridge oscillators) are used. The following denote: L = Inductance Unit: Henry (H) C = Capacitance Unit: Farad (F) R = Resistance Unit: Ohm Ω 1 H = 1 Vs/A 1 F = 1 As/V 1 Ω...
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