Analogue and digital lock-in techniques for very-low-frequency impedance spectroscopy

Albertini, A; Kleemann, W.

doi:10.1088/0957-0233/8/6/014

Cited by 16 publications

(9 citation statements)

References 15 publications

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“…As such, it has become a popular signal processing tool for measurement systems in a wide range of applications, particularly those that suffer from low signal-to-noise performance. Specifically, lock-in detection has been implemented in biomedical instrumentation to measure tissue conductivity and permittivity in electrical impedance tomography, 29 electrical impedance spectroscopy, 30,31 and optical spectrometry. 32,33 However, even in these more advanced systems, the lock-in detection schemes and signal operations are executed in the analog domain.…”

Section: Analog Detectionmentioning

confidence: 99%

Digital-signal-processor-based dynamic imaging system for optical tomography

Lasker

Masciotti

Schoenecker

et al. 2007

Review of Scientific Instruments

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In this article, we introduce a dynamic optical tomography system that is, unlike currently available analog instrumentation, based on digital data acquisition and filtering techniques. At the core of this continuous wave instrument is a digital signal processor (DSP) that collects, collates, processes, and filters the digitized data set. The processor is also responsible for managing system timing and the imaging routines which can acquire real-time data at rates as high as 150 Hz. Many of the synchronously timed processes are controlled by a complex programmable logic device that is also used in conjunction with the DSP to orchestrate data flow. The operation of the system is implemented through a comprehensive graphical user interface designed with LABVIEW software which integrates automated calibration, data acquisition, data organization, and signal postprocessing. Performance analysis demonstrates very low system noise (approximately 1 pW rms noise equivalent power), excellent signal precision (<0.04%-0.2%) and long term system stability (<1% over 40 min). A large dynamic range (approximately 190 dB) accommodates a wide scope of measurement geometries and tissue types. First experiments on tissue phantoms show that dynamic behavior is accurately captured and spatial location can be correctly tracked using this system.

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Section: Analog Detectionmentioning

confidence: 99%

Digital-signal-processor-based dynamic imaging system for optical tomography

Lasker

Masciotti

Schoenecker

et al. 2007

Review of Scientific Instruments

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“…Individual low frequency range measurement cycles take seconds-minutes to complete resulting in long cycle durations compared to high frequency tests. Increased low frequency measurement time can be reduced by combining frequencies into a multi-sine signal, but such an approach complicates analysis (Nam et al 2013) and may increase vulnerability to electromagnetic interference (Albertini and Kleemann 1997). In contrast, identification and measurement of a small number of key frequencies where biomarker binding causes significant impedance changes can reduce measurement time without compromising functionality (Daniels and Pourmand 2007).…”

Section: Introductionmentioning

confidence: 99%

POISED-5, a portable on-board electrochemical impedance spectroscopy biomarker analysis device

Sawhney

Conlan

2019

Biomed Microdevices

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Point-of-care medical devices offer the potential for rapid biomarker detection and reporting of medical conditions, thereby bypassing the requirements for offline clinical laboratory facilities in many cases. Label-free electrochemical techniques are suitable for use in handheld diagnostic devices due the inherent electronic detection modality and low requirement for processing reagents. While electrochemical impedance sensing is widely used in tissue analysis such as body composition measurement, its use in point-of-care patient testing is yet to be widely adopted. Here we have considered a number of issues currently limiting the translation of electrochemical impedance sensing into clinical biosensor devices. Specifically, we have addressed the current requirement for these sensors to be connected to an external processor by applying a minimum number of frequencies required for optimized biomarker detection, and subsequently delivering analytics within the measurement device. The POISED-5 device was evaluated using a sensor for the ovarian cancer biomarker cancer antigen 125 (CA125), demonstrating performance comparable to standard laboratory equipment, with direct interpretation of response signal amplitude substituting traditional impedance component calculation and model fitting.

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“…In particular, performances at low frequencies are significantly better. The field of applications which require the detection of very low signals in noisy surroundings where the use of lock-in detectors from optics is widespread (Andersson et al, 2007;Masciotti et al, 2008;Holzman et al, 2005), impedance spectroscopy (Albertini and Kleemann, 1997), wireless networks (Gabal et al, 2010), biologic applications (Ferri et al, 2001;Johnson et al, 2002), electron spin resonance (ESR) (Vistnes et al, 1984;Murányi et al, 2004) to nuclear magnetic resonance (NMR) (Saam and Conradi, 1998;Caracappa and Thorn, 2003).…”

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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Analogue and digital lock-in techniques for very-low-frequency impedance spectroscopy

Cited by 16 publications

References 15 publications

Digital-signal-processor-based dynamic imaging system for optical tomography

Digital-signal-processor-based dynamic imaging system for optical tomography

POISED-5, a portable on-board electrochemical impedance spectroscopy biomarker analysis device

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

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