Advances in lock-in amplifiers

Meade, MO

doi:10.1088/0022-3735/15/4/001

Cited by 101 publications

(56 citation statements)

References 5 publications

(2 reference statements)

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“…Additionally, sometimes what is needed in a measurement is the phase shift between the reference and input signals. To meet these needs a cue is taken from dual-phase, lock-in amplifiers 14 and in addition to our reference waveform a quadrature signal, which is just the reference waveform shifted by 90…”

Section: Phase Shifts and Mixingmentioning

confidence: 99%

Phase-sensitive detection in the undergraduate lab using a low-cost microcontroller

Schultz

2016

American Journal of Physics

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Phase-sensitive detection (PSD) is an important experimental technique that allows signals to be extracted from noisy data. PSD is also used in modulation spectroscopy and is used in the stabilization of optical sources. Commercial lock-in amplifiers that use PSD are often expensive and host a bewildering array of controls that may intimidate a novice user. Low-cost microcontrollers such as the Arduino family of devices seem like a good match for learning about PSD; however, making a self-contained device (reference signal, voltage input, mixing, filtering, and display) is difficult, but in the end the project teaches students "tricks" to turn the Arduino into a true scientific instrument.

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Section: Phase Shifts and Mixingmentioning

confidence: 99%

Phase-sensitive detection in the undergraduate lab using a low-cost microcontroller

Schultz

2016

American Journal of Physics

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“…Lock-in detectors working with the principle of phasesensitive detection are widely used to retrieve small signals from a huge noise floor (Meade, 1982(Meade, , 1983Blair and Sydenham, 1975). The signal to be measured is modulated by a reference frequency.…”

Section: Introductionmentioning

confidence: 99%

A remote-control datalogger for large-scale resistivity surveys and robust processing of its signals using a software lock-in approach

Oppermann¹,

Günther²

2018

Geosci. Instrum. Method. Data Syst.

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Abstract. We present a new versatile datalogger that can be used for a wide range of possible applications in geosciences. It is adjustable in signal strength and sampling frequency, battery saving and can remotely be controlled over a Global System for Mobile Communication (GSM) connection so that it saves running costs, particularly in monitoring experiments. The internet connection allows for checking functionality, controlling schedules and optimizing pre-amplification. We mainly use it for large-scale electrical resistivity tomography (ERT), where it independently registers voltage time series on three channels, while a square-wave current is injected. For the analysis of this time series we present a new approach that is based on the lock-in (LI) method, mainly known from electronic circuits. The method searches the working point (phase) using three different functions based on a mask signal, and determines the amplitude using a direct current (DC) correlation function. We use synthetic data with different types of noise to compare the new method with existing approaches, i.e. selective stacking and a modified fast Fourier transformation (FFT)-based approach that assumes a 1/f noise characteristics. All methods give comparable results, but the LI is better than the well-established stacking method. The FFT approach can be even better but only if the noise strictly follows the assumed characteristics. If overshoots are present in the data, which is typical in the field, FFT performs worse even with good data, which is why we conclude that the new LI approach is the most robust solution. This is also proved by a field data set from a long 2-D ERT profile.

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“…A reference signal is created in accordance with an expected measured signal and is compared with it. Depending on the implementation of the lock-in method there are several possibilities of generation of a reference signal as well as its synchronization with the measured signal [11]. In this investigation we will analyze the problems of synchronization or rather non-synchronization of the external reference signal and the measured signal in particular in the frame of its usage in the (bio)impedance measurement method.…”

Section: Introductionmentioning

confidence: 99%

“…In cases where a signal is accompanied by broad band noise it is feasible to generate reference signal externally instead of using excitation signal as reference. In this case the phase sensitive detector responds also to harmonic components of the excitation signal even though the fundamental component is well defined [11]. Bioimpedance as defined in the electrical circuit theory is essentially a transfer impedance, determined as a ratio of a voltage and a current complexor which are not necessarily related to the same nodes [5].…”

Section: Introductionmentioning

confidence: 99%

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Frequency Synchronization Analysis in Digital lock-in Methods for Bio-impedance Determination

Brajkovič

Žagar

Križaj

2014

Measurement Science Review

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The lock-in method is one of the most frequently used methods for reconstruction of measured signals and as such frequently applied in the (bio)impedance method to determine the modulus and phase of the (bio)impedance. In implementation of the method in a (bio)impedance measurement device one has to consider possible non synchronized frequencies of the reference and the analyzed signals as well as potential sources of noise. In this work we analyzed these errors theoretically and experimentally. We show that both amplitude and phase errors depend on the relative difference of the frequencies of the reference and investigated signal as well as the number of integration periods. Theoretically, these errors vanish during the determination of the (bio)impedance modulus and phase. In practical implementation the inaccuracies appear at points of very low determined signal amplitudes due to the limited accuracy of analog to digital converters and are distributed around these points due to other sources of noise inherent in implementation of the measurement device.

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Advances in lock-in amplifiers

Cited by 101 publications

References 5 publications

Phase-sensitive detection in the undergraduate lab using a low-cost microcontroller

Phase-sensitive detection in the undergraduate lab using a low-cost microcontroller

A remote-control datalogger for large-scale resistivity surveys and robust processing of its signals using a software lock-in approach

Frequency Synchronization Analysis in Digital lock-in Methods for Bio-impedance Determination

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