Phase sensitive measurement
Phase sensitive measurement measurement in which the phase of an ac signal is tracked in a feedback loop in order to improve detection sensitivity. The most common ex- amples are phase-locked loops in control systems and lock-in amplifier measurements in electronics. In the latter, a small ac signal is added to the bias voltage supply, and this signal is then detected in any measured quantity with an amplifier whose phase can be varied to “lock onto” that of the initial ac signal. This effectively mixes the two ac signals, and their difference (at dc) is used to characterize the measurement. The effective bandwidth is determined by the bandwidth at the dc level.
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Author of the text: Ed. P.A. Laplante Boca Raton: CRC Press LLC, 2000
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