Comparison of Howland and General Impedance Converter (GIC) circuit based current sources for bio-impedance measurements

Qureshi, Tabassum-Ur-Razaq; Chatwin, Chris; Huber, Nicolas; Zarafshani, Ali; Tunstall, B.; Wang, Wei

doi:10.1088/1742-6596/224/1/012167

Cited by 16 publications

(7 citation statements)

References 5 publications

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“…The proposed system has a current source to excite the MUT, thus assuring maximum resolution and health safety. The Enhanced Howland Current Sources (EHCS) [36] and its modifications (mirrored [37], load-in-the-loop [38], NIC [39], GIC [40], lead-lag [36], and differential [41]) are the preferred current sources in bioimpedance measurements because they show higher cost-benefit (regarding number of active components, stability, output impedance, output compliance and output common mode) than other circuits. Nevertheless, alternative current sources exist, it can be simpler than the EHCS [42] or even integrated [37].…”

Section: Current Sourcementioning

confidence: 99%

Design and Evaluation of an Electrical Bioimpedance Device Based on DIBS for Myography during Isotonic Exercises

Sirtoli

Morcelles

Gomez

et al. 2018

JLPEA

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Electrical Bioimpedance Spectroscopy (EIS) is a technique used to assess passive electrical properties of biological materials. EIS detects physiological and pathological conditions in animal tissues. Recently, the introduction of broadband excitation signals has reduced the measuring time for application techniques such as Electrical Bioimpedance Myography. Therefore, this work is aimed at proposing a prototype by using discrete interval binary sequences (DIBS), which is based on a system that holds a current source, impedance acquisition system, microcontroller and graphical user interface. Measurements between 5 Ω to 5 kΩ had impedance acquisition and phase angle errors of aproximately 2% and were lower than 3 degrees, respectively. Based on a proposed circuit, bioimpedance of the chest muscle (Pectoralis Major) was measured during isotonic exercise (push-up). As a result, our analyses have detected tiredness and fatigue. We have explored and proposed new parameters which assess such conditions, as both the maximum magnitude and tiredness coefficient. These parameters decrease exponentially with consecutive push-ups and were convergent in the majority of the sixteen days of measurement.

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Section: Current Sourcementioning

confidence: 99%

Design and Evaluation of an Electrical Bioimpedance Device Based on DIBS for Myography during Isotonic Exercises

Sirtoli

Morcelles

Gomez

et al. 2018

JLPEA

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show abstract

“…However, since the load impedance of tissue is frequency-dependent, the current source must deliver a constant current through a wide range of frequencies, while maintaining a suitable output to load impedance ratio. Design configurations examined for bioimpedance measurements have included the use of current mirrors, MHCPs, and current conveyors [23,[25][26][27][28][29][30][31][32][33].…”

Section: System Designmentioning

confidence: 99%

Design of Bioimpedance Spectroscopy Instrument With Compensation Techniques for Soft Tissue Characterization

Dodde

Kruger

Shih

2015

Journal of Medical Devices

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Bioimpedance spectroscopy (BIS) has shown significant potential in many areas of medicine to provide new physiologic markers. Several acute and chronic diseases are accompanied by changes in intra- and extracellular fluid within various areas of the human body. The estimation of fluid in various body compartments is therefore a simple and convenient method to monitor certain disease states. In this work, the design and evaluation of a BIS instrument are presented and three key areas of the development process investigated facilitating the BIS measurement of tissue hydration state. First, the benefit of incorporating DC-stabilizing circuitry to the standard modified Howland current pump (MHCP) is investigated to minimize the effect of DC offsets limiting the dynamic range of the system. Second, the influence of the distance between the bioimpedance probe and a high impedance material is investigated using finite element analysis (FEA). Third, an analytic compensation technique is presented to minimize the influence of parasitic capacitance. Finally, the overall experimental setup is evaluated through ex vivo BIS measurements of porcine spleen tissue and compared to published results. The DC-stabilizing circuit demonstrated its ability to maintain DC offsets at less than 650 μV through 100 kHz while maintaining an output impedance of 1 MΩ from 100 Hz to 100 kHz. The proximity of a bioimpedance probe to a high impedance material such as acrylic was shown to increase measured impedance readings by a factor of 4x as the ratio of the distance between the sensing electrodes to the distance between the bioimpedance probe and acrylic reached 1:3. The average parasitic capacitance for the circuit presented was found to be 712 ± 128 pF, and the analytic compensation method was shown to be able to minimize this effect on the BIS measurements. Measurements of porcine spleen tissue showed close correlation with experimental results reported in published articles. This research presents the successful design and evaluation of a BIS instrument. Specifically, robust measurements were obtained by implementing a DC-stabilized current source, investigating probe-material proximity issues and compensating for parasitic capacitance. These strategies were shown to provide tissue measurements comparable with published literature.

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“…In bioimpedance applications most systems use a voltage controlled current source (VCCS), usually the enhanced Howland current source (EHCS), because it has shown to be very simple and robust [ 10 ]. A few modifications have been proposed to this circuit such as: Mirrored [ 11 ] and Bridge [ 12 ] configurations, Load-in-the-loop [ 13 ], NIC [ 14 ] and GIC [ 15 ] output stages, high frequency compensations such as Lead-Lag circuits [ 10 ], and by using differential amplifiers as the active components [ 16 ]. However, most of these improvements focus in the output impedance and bandwidth flatness, leaving characteristics like swing and load common mode voltage aside.…”

Section: Introductionmentioning

confidence: 99%

Design of current sources for load common mode optimization

Sirtoli

Morcelles

Vincence

2018

Journal of Electrical Bioimpedance

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Bioimpedance measurement systems often use the Howland current sources to excite the biological material under study. Usually, difference or instrumentation amplifiers are used to measure the resulting voltage drop on this material. In these circuits, common mode voltage appears as artifacts in the measurement. Most researches on current sources are focused on improving the output impedance, letting other characteristics aside. In this paper, it is made a brief review on the load common mode voltage and output swing of various topologies of Howland current sources. Three circuits are proposed to reduce load common mode voltage and enhance load capability by using a fully differential amplifier as active component. These circuits are equated, simulated and implemented. The three proposed circuits were able to deliver an output current with cut-off frequency (-3dB) higher than 1 MHz for loads as big as 4.7 kΩ. The worst measured load common mode voltage was smaller than 24 mV for one of the circuits and smaller than 8 mV for the other two. Consequently, it could be obtained increases in the Common Mode Rejection Ratio (CMRR) up to 60 dB when compared to the Enhanced Howland Current Source (EHCS).

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Comparison of Howland and General Impedance Converter (GIC) circuit based current sources for bio-impedance measurements

Cited by 16 publications

References 5 publications

Design and Evaluation of an Electrical Bioimpedance Device Based on DIBS for Myography during Isotonic Exercises

Design and Evaluation of an Electrical Bioimpedance Device Based on DIBS for Myography during Isotonic Exercises

Design of Bioimpedance Spectroscopy Instrument With Compensation Techniques for Soft Tissue Characterization

Design of current sources for load common mode optimization

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