Signal Conditioning

Photo Optical Modulator

Photo Optical Modulator: Photo Optical Modulator – The principle of an optical dc chopper is illustrated in Fig. 14.42. Devices of this type have been used widely in infrared signal detectors, whose output is a slowly varying dc product. The properties of the parallel connected photo re­sistor are such that the device produces a decrease …

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Varactor Diode Symbol

Varactor Diode Symbol: A specially processed junction diode that assumes the properties of a variable capacitor (about 5 – 250 pf) when its dc reverse voltage is varied is called a Varactor Diode shown in Fig. 14.37. This unique behavior can be used in special modulator circuits designed to turn a low voltage dc signal …

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Magnetic Modulator

Magnetic Modulator: The most reliable substitutes for electromechanical choppers are magnetic modulators. These devices reach a null stability as low as 10 μV, but their response time is often less than 2 Hz and the ambient temperature range is restricted. The 3-leg saturable reactor, shown in Fig. 14.32 falls within the cat­egory of magnetic modulator …

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Self Oscillating Converter (Transistorized Chopper Circuit)

Self Oscillating Converter (Transistorized Chopper Circuit): Self Oscillating Converter (Transistorized Chopper Circuit) – A Transistorized dc to ac converter suitable for low level dc signal is illustrated in Fig. 14.30. The unique property of this assembly is that it starts to oscillate vigorously at very low levels of dc collector voltages at only a few …

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