Accuracy study for lock‐in amplifiers in a scanning near‐infrared spectrometer

Wang, Jingru; Lui, Jie; Wang, Zhihong; Liu, Guangda

doi:10.1049/iet-smt.2016.0440

Cited by 2 publications

(2 citation statements)

References 21 publications

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“…As shown in Equation ( 8), the actually measured amplitude of signal Ã has error due to the frequency deviation ∆ f [28]. Furthermore, taking the IAF as an example for quantitatively analyzing the amplitude measurement error caused by frequency deviation ∆ f , ignoring the noise n(t), Equations ( 4) and ( 5) can be rewritten as :…”

Section: Principle Of Lock-in Amplifier and Frequency Error Analysismentioning

confidence: 99%

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A Software Digital Lock-In Amplifier Method with Automatic Frequency Estimation for Low SNR Multi-Frequency Signal

et al. 2022

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In the fault diagnosis field, the fault feature signal is weak and contaminated by the noise. The lock-in amplifier is a useful tool for weak signal detection. Aiming to the amplitude error of the lock-in amplifier caused by frequency deviation between the measured signal and the reference signal, a DFT-based automatic signal frequency estimation method is studied to improve the frequency accuracy of the reference signal. Based on this frequency estimation method, a software digital lock-in amplifier method is proposed to detect the multiple frequencies signals. This proposed method can automatically measure the frequency value of the measured signal without prior frequency information. Then, the reference signals are generated through this frequency value to make the digital lock-in amplifier estimate the amplitude of the measured signal. Moreover, an iterative structure is used to implement the multiple frequencies signal measurement. The frequencies and amplitudes measurement accuracies are tested. Under different SNR conditions, the frequency relative error is less than 0.1%. In addition, the amplitude relative error with different signal frequencies is less than 1.7% when the SNR is −1 dB. This proposed software digital lock-in amplifier method has a higher signal frequency tracking ability and amplitude measurement accuracy.

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Section: Principle Of Lock-in Amplifier and Frequency Error Analysismentioning

confidence: 99%

“…is the period of reference signals. Then, the amplitude estimation value with frequency deviation ∆ f can be obtained [28]:…”

Section: Principle Of Lock-in Amplifier and Frequency Error Analysismentioning

confidence: 99%

A Software Digital Lock-In Amplifier Method with Automatic Frequency Estimation for Low SNR Multi-Frequency Signal

et al. 2022

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Note: Demodulation of spectral signal modulated by optical chopper with unstable modulation frequency

Zhang

Wang

et al. 2017

Review of Scientific Instruments

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When an optical chopper is used to modulate the light source, the rotating speed of the wheel may vary with time and subsequently cause jitter of the modulation frequency. The amplitude calculated from the modulated signal would be distorted when the frequency fluctuations occur. To precisely calculate the amplitude of the modulated light flux, we proposed a method to estimate the range of the frequency fluctuation in the measurement of the spectrum and then extract the amplitude based on the sum of power of the signal in the selected frequency range. Experiments were designed to test the feasibility of the proposed method and the results showed lower root means square error than the conventional way.

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Accuracy study for lock‐in amplifiers in a scanning near‐infrared spectrometer

Cited by 2 publications

References 21 publications

A Software Digital Lock-In Amplifier Method with Automatic Frequency Estimation for Low SNR Multi-Frequency Signal

A Software Digital Lock-In Amplifier Method with Automatic Frequency Estimation for Low SNR Multi-Frequency Signal

Note: Demodulation of spectral signal modulated by optical chopper with unstable modulation frequency

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