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Nguyen XT, Ali M, Lee JW. 3.6 mW Active-Electrode ECG/ETI Sensor System Using Wideband Low-Noise Instrumentation Amplifier and High Impedance Balanced Current Driver. SENSORS (BASEL, SWITZERLAND) 2023; 23:2536. [PMID: 36904738 PMCID: PMC10007594 DOI: 10.3390/s23052536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/17/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
An active electrode (AE) and back-end (BE) integrated system for enhanced electrocardiogram (ECG)/electrode-tissue impedance (ETI) measurement is proposed. The AE consists of a balanced current driver and a preamplifier. To increase the output impedance, the current driver uses a matched current source and sink, which operates under negative feedback. To increase the linear input range, a new source degeneration method is proposed. The preamplifier is realized using a capacitively-coupled instrumentation amplifier (CCIA) with a ripple-reduction loop (RRL). Compared to the traditional Miller compensation, active frequency feedback compensation (AFFC) achieves bandwidth extension using the reduced size of the compensation capacitor. The BE performs three types of signal sensing: ECG, band power (BP), and impedance (IMP) data. The BP channel is used to detect the Q-, R-, and S-wave (QRS) complex in the ECG signal. The IMP channel measures the resistance and reactance of the electrode-tissue. The integrated circuits for the ECG/ETI system are realized in the 180 nm CMOS process and occupy a 1.26 mm2 area. The measured results show that the current driver supplies a relatively high current (>600 μApp) and achieves a high output impedance (1 MΩ at 500 kHz). The ETI system can detect resistance and capacitance in the ranges of 10 mΩ-3 kΩ and 100 nF-100 μF, respectively. The ECG/ETI system consumes 3.6 mW using a single 1.8 V supply.
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Zhu F, Jiang L, Dong G, Gao X, Wang Y. An Open Dataset for Wearable SSVEP-Based Brain-Computer Interfaces. SENSORS 2021; 21:s21041256. [PMID: 33578754 PMCID: PMC7916479 DOI: 10.3390/s21041256] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 02/07/2021] [Accepted: 02/08/2021] [Indexed: 11/20/2022]
Abstract
Brain-computer interfaces (BCIs) provide humans a new communication channel by encoding and decoding brain activities. Steady-state visual evoked potential (SSVEP)-based BCI stands out among many BCI paradigms because of its non-invasiveness, little user training, and high information transfer rate (ITR). However, the use of conductive gel and bulky hardware in the traditional Electroencephalogram (EEG) method hinder the application of SSVEP-based BCIs. Besides, continuous visual stimulation in long time use will lead to visual fatigue and pose a new challenge to the practical application. This study provides an open dataset, which is collected based on a wearable SSVEP-based BCI system, and comprehensively compares the SSVEP data obtained by wet and dry electrodes. The dataset consists of 8-channel EEG data from 102 healthy subjects performing a 12-target SSVEP-based BCI task. For each subject, 10 consecutive blocks were recorded using wet and dry electrodes, respectively. The dataset can be used to investigate the performance of wet and dry electrodes in SSVEP-based BCIs. Besides, the dataset provides sufficient data for developing new target identification algorithms to improve the performance of wearable SSVEP-based BCIs.
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Affiliation(s)
- Fangkun Zhu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Tianjin Key Laboratory of Bioelectromagnetic Technology and Intelligent Health, Hebei University of Technology, Tianjin 300132, China;
| | - Lu Jiang
- State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China;
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guoya Dong
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Tianjin Key Laboratory of Bioelectromagnetic Technology and Intelligent Health, Hebei University of Technology, Tianjin 300132, China;
- Correspondence: (G.D.); (Y.W.)
| | - Xiaorong Gao
- School of Medicine, Tsinghua University, Beijing 100084, China;
| | - Yijun Wang
- State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China;
- University of Chinese Academy of Sciences, Beijing 100049, China
- Correspondence: (G.D.); (Y.W.)
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Wearable Active Electrode for sEMG Monitoring Using Two-Channel Brass Dry Electrodes with Reduced Electronics. JOURNAL OF HEALTHCARE ENGINEERING 2020; 2020:5950218. [PMID: 32802299 PMCID: PMC7416295 DOI: 10.1155/2020/5950218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 06/26/2020] [Accepted: 07/14/2020] [Indexed: 11/17/2022]
Abstract
Gel-based electrodes are employed to record sEMG signals for prolonged periods. These signals are used for the control of myoelectric prostheses, clinical analysis, or sports medicine. However, when the gel dries, the electrode-skin impedance increases considerably. Using dry active electrodes (AEs) to compensate variations of impedance is an alternative for long-term recording. This work describes the optimization of the electronic design of a conventional AE by removing the impedance coupling stage and two filters. The proposed work consisted of 5 stages: electrodes, amplification (X250), 2.2 Vdc offset, low-pass filter, and ADC with USART communication. The device did not need the use of electrolytic gel. The measurements of CMRR (96 dB), amplitude of the output sEMG signal (∼1.6 Vp-p), and system bandwidth (15-450 Hz) were performed in order to confirm the reliability of the device as an sEMG signal acquisition system. The SNR values from seven movements performed by eleven volunteers were compared in order to measure the repeatability of the measurements (average 30.32 dB for a wrist flexion). The SNR for wrist flexion measured with the proposed and the commercial system was compared; the values were 49 dB and 60 dB, respectively.
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Wearable and Flexible Textile Electrodes for Biopotential Signal Monitoring: A review. ELECTRONICS 2019. [DOI: 10.3390/electronics8050479] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Wearable electronics is a rapidly growing field that recently started to introduce successful commercial products into the consumer electronics market. Employment of biopotential signals in wearable systems as either biofeedbacks or control commands are expected to revolutionize many technologies including point of care health monitoring systems, rehabilitation devices, human–computer/machine interfaces (HCI/HMIs), and brain–computer interfaces (BCIs). Since electrodes are regarded as a decisive part of such products, they have been studied for almost a decade now, resulting in the emergence of textile electrodes. This study presents a systematic review of wearable textile electrodes in physiological signal monitoring, with discussions on the manufacturing of conductive textiles, metrics to assess their performance as electrodes, and an investigation of their application in the acquisition of critical biopotential signals for routine monitoring, assessment, and exploitation of cardiac (electrocardiography, ECG), neural (electroencephalography, EEG), muscular (electromyography, EMG), and ocular (electrooculography, EOG) functions.
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Yip YWY, Man TC, Pang CP, Brelén ME. Improving the quality of electroretinogram recordings using active electrodes. Exp Eye Res 2018; 176:46-52. [PMID: 29908144 DOI: 10.1016/j.exer.2018.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 06/09/2018] [Accepted: 06/12/2018] [Indexed: 11/27/2022]
Abstract
The aim of this study was to compare the quality of electroretinogram (ERG) recordings using a custom built active electrode with attached amplifier versus a standard (passive) ERG electrode. Scotopic and photopic ERG responses were recorded from five adult albino rabbits using a custom built active electrode on one eye and a passive electrode on the other. For the active electrode, the ERG-jet electrode (Universo S.A., La Chaux-De-Fonds, Switzerland) was used as the transducer with the cable cut short and soldered directly to the input of a customized amplifier. The passive electrode was a standard ERG jet electrode. The signal to noise ratio and reproducibility of ERGs were compared. The noise was significantly lower in the active electrode compared to the passive electrode (p = 0.009) resulting in signals being recorded at lower stimulation strengths with the active electrode. The scotopic a-wave was significantly larger in the active electrode at all supra-threshold stimulation intensities (p < 0.05) and the scotopic b-wave amplitudes were also higher in the active electrode at all supra-threshold stimulation intensities but was only statistically significant between -3.25 and -1 log cd.s.m-2 (p < 0.05). The photopic a- and b-wave amplitudes were also higher in the active electrode and statistically significant between -0.75 and 0.48 log cd.s.m-2 for the a-wave and -1.25 to -1 log cd.s.m-2 for the b-wave (p < 0.05). The intra-observer repeatability, inter-sessions reproducibility and reliability of the signals were better in the active electrode as evidenced by lower coefficient of variation (CV) and coefficient of repeatability (CR) with high intra-class correlation coefficient (ICC) of the a- and b-wave parameters of the active electrode. These findings suggest that the custom built active ERG electrode produces less noise than the passive electrode, allowing responses to be recorded at lower stimulation strengths. It produces greater signal amplitudes and improved reproducibility and is therefore a better device for investigating retinal function.
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Affiliation(s)
- Yolanda Wong Ying Yip
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Tsz Chun Man
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Chi Pui Pang
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China; Shantou University/Chinese University of Hong Kong Joint Shantou International Eye Center, Shantou, China
| | - Mårten Erik Brelén
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China; Shantou University/Chinese University of Hong Kong Joint Shantou International Eye Center, Shantou, China; Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
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Guerrero FN, Spinelli EM, Haberman MA. Analysis and Simple Circuit Design of Double Differential EMG Active Electrode. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2016; 10:787-795. [PMID: 26841414 DOI: 10.1109/tbcas.2015.2492944] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this paper we present an analysis of the voltage amplifier needed for double differential (DD) sEMG measurements and a novel, very simple circuit for implementing DD active electrodes. The three-input amplifier that standalone DD active electrodes require is inherently different from a differential amplifier, and general knowledge about its design is scarce in the literature. First, the figures of merit of the amplifier are defined through a decomposition of its input signal into three orthogonal modes. This analysis reveals a mode containing EMG crosstalk components that the DD electrode should reject. Then, the effect of finite input impedance is analyzed. Because there are three terminals, minimum bounds for interference rejection ratios due to electrode and input impedance unbalances with two degrees of freedom are obtained. Finally, a novel circuit design is presented, including only a quadruple operational amplifier and a few passive components. This design is nearly as simple as the branched electrode and much simpler than the three instrumentation amplifier design, while providing robust EMG crosstalk rejection and better input impedance using unity gain buffers for each electrode input. The interference rejection limits of this input stage are analyzed. An easily replicable implementation of the proposed circuit is described, together with a parameter design guideline to adjust it to specific needs. The electrode is compared with the established alternatives, and sample sEMG signals are obtained, acquired on different body locations with dry contacts, successfully rejecting interference sources.
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Lo CC, Chien TY, Chen YC, Tsai SH, Fang WC, Lin BS. A Wearable Channel Selection-Based Brain-Computer Interface for Motor Imagery Detection. SENSORS 2016; 16:213. [PMID: 26861347 PMCID: PMC4801589 DOI: 10.3390/s16020213] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/02/2016] [Indexed: 11/16/2022]
Abstract
Motor imagery-based brain-computer interface (BCI) is a communication interface between an external machine and the brain. Many kinds of spatial filters are used in BCIs to enhance the electroencephalography (EEG) features related to motor imagery. The approach of channel selection, developed to reserve meaningful EEG channels, is also an important technique for the development of BCIs. However, current BCI systems require a conventional EEG machine and EEG electrodes with conductive gel to acquire multi-channel EEG signals and then transmit these EEG signals to the back-end computer to perform the approach of channel selection. This reduces the convenience of use in daily life and increases the limitations of BCI applications. In order to improve the above issues, a novel wearable channel selection-based brain-computer interface is proposed. Here, retractable comb-shaped active dry electrodes are designed to measure the EEG signals on a hairy site, without conductive gel. By the design of analog CAR spatial filters and the firmware of EEG acquisition module, the function of spatial filters could be performed without any calculation, and channel selection could be performed in the front-end device to improve the practicability of detecting motor imagery in the wearable EEG device directly or in commercial mobile phones or tablets, which may have relatively low system specifications. Finally, the performance of the proposed BCI is investigated, and the experimental results show that the proposed system is a good wearable BCI system prototype.
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Affiliation(s)
- Chi-Chun Lo
- Institute of Electrical and Control Engineering, National Chiao Tung University, Hsinchu 300, Taiwan.
- Department of Engineering and Maintenance, Chang Gung Memorial Hospital, Kaohsiung 833, Taiwan.
| | - Tsung-Yi Chien
- Department of Engineering and Maintenance, Chang Gung Memorial Hospital, Kaohsiung 833, Taiwan.
| | - Yu-Chun Chen
- Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan 711, Taiwan.
| | - Shang-Ho Tsai
- Institute of Electrical and Control Engineering, National Chiao Tung University, Hsinchu 300, Taiwan.
| | - Wai-Chi Fang
- Department of Electronics Egineering, National Chiao Tung University, Hsinchu 300, Taiwan.
| | - Bor-Shyh Lin
- Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan 711, Taiwan.
- Department of Medical Research, Chi-Mei Medical Center, Tainan 710, Taiwan.
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Soft, comfortable polymer dry electrodes for high quality ECG and EEG recording. SENSORS 2014; 14:23758-80. [PMID: 25513825 PMCID: PMC4299086 DOI: 10.3390/s141223758] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 11/22/2014] [Accepted: 12/02/2014] [Indexed: 12/27/2022]
Abstract
Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes offering high user comfort, since they are fabricated from EPDM rubber containing various additives for optimum conductivity, flexibility and ease of fabrication. The electrode impedance is measured on phantoms and human skin. After optimization of the polymer composition, the skin-electrode impedance is only ~10 times larger than that of gel electrodes. Therefore, these electrodes are directly capable of recording strong biopotential signals such as ECG while for low-amplitude signals such as EEG, the electrodes need to be coupled with an active circuit. EEG recordings using active polymer electrodes connected to a clinical EEG system show very promising results: alpha waves can be clearly observed when subjects close their eyes, and correlation and coherence analyses reveal high similarity between dry and gel electrode signals. Moreover, all subjects reported that our polymer electrodes did not cause discomfort. Hence, the polymer-based dry electrodes are promising alternatives to either rigid dry electrodes or conventional gel electrodes.
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Fuketa H, Yoshioka K, Shinozuka Y, Ishida K, Yokota T, Matsuhisa N, Inoue Y, Sekino M, Sekitani T, Takamiya M, Someya T, Sakurai T. 1 μm-thickness ultra-flexible and high electrode-density surface electromyogram measurement sheet with 2 V organic transistors for prosthetic hand control. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2014; 8:824-833. [PMID: 24951707 DOI: 10.1109/tbcas.2014.2314135] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A 64-channel surface electromyogram (EMG) measurement sheet (SEMS) with 2 V organic transistors on a 1 μm-thick ultra-flexible polyethylene naphthalate (PEN) film is developed for prosthetic hand control. The surface EMG electrodes must satisfy the following three requirements; high mechanical flexibility, high electrode density and high signal integrity. To achieve high electrode density and high signal integrity, a distributed and shared amplifier (DSA) architecture is proposed, which enables an in-situ amplification of the myoelectric signal with a fourfold increase in EMG electrode density. In addition, a post-fabrication select-and-connect (SAC) method is proposed to cope with the large mismatch of organic transistors. The proposed SAC method reduces the area and the power overhead by 96% and 98.2%, respectively, compared with the use of conventional parallel transistors to reduce the transistor mismatch by a factor of 10.
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Huang YJ, Wu CY, Wong AMK, Lin BS. Novel active comb-shaped dry electrode for EEG measurement in hairy site. IEEE Trans Biomed Eng 2014; 62:256-63. [PMID: 25137719 DOI: 10.1109/tbme.2014.2347318] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electroencephalography (EEG) is an important biopotential, and has been widely applied in clinical applications. The conventional EEG electrode with conductive gels is usually used for measuring EEG. However, the use of conductive gel also encounters with the issue of drying and hardening. Recently, many dry EEG electrodes based on different conductive materials and techniques were proposed to solve the previous issue. However, measuring EEG in the hairy site is still a difficult challenge. In this study, a novel active comb-shaped dry electrode was proposed to measure EEG in hairy site. Different form other comb-shaped or spike-shaped dry electrodes, it can provide more excellent performance of avoiding the signal attenuation, phase distortion, and the reduction of common mode rejection ratio. Even under walking motion, it can effectively acquire EEG in hairy site. Finally, the experiments for alpha rhythm and steady-state visually evoked potential were also tested to validate the proposed electrode.
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Abstract
Patient biopotentials are usually measured with conventional disposable Ag/AgCl electrodes. These electrodes provide excellent signal quality but are irritating for long-term use. Skin preparation is usually required prior to the application of electrodes such as shaving and cleansing with alcohol. To overcome these difficulties, researchers and caregivers seek alternative electrodes that would be acceptable in clinical and research environments. Dry electrodes that operate without gel, adhesive or even skin preparation have been studied for many decades. They are used in research applications, but they have yet to achieve acceptance for medical use. So far, a complete comparison and evaluation of dry electrodes is not well described in the literature. This work compares dry electrodes for biomedical use and physiological research, and reviews some novel systems developed for cardiac monitoring. Lastly, the paper provides suggestions to develop a dry-electrode-based system for mobile and long-term cardiac monitoring applications.
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Affiliation(s)
- N Meziane
- Department of Biomedical Engineering, University of Wisconsin–Madison, 1550 Engineering Dr., Madison, WI 53706-1609, USA.
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12
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Design, fabrication and characterization of a low-impedance 3D electrode array system for neuro-electrophysiology. SENSORS 2012. [PMID: 23208555 PMCID: PMC3571798 DOI: 10.3390/s121216571] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent progress in patterned microelectrode manufacturing technology and microfluidics has opened the way to a large variety of cellular and molecular biosensor-based applications. In this extremely diverse and rapidly expanding landscape, silicon-based technologies occupy a special position, given their statute of mature, consolidated, and highly accessible areas of development. Within the present work we report microfabrication procedures and workflows for 3D patterned gold-plated microelectrode arrays (MEA) of different shapes (pyramidal, conical and high aspect ratio), and we provide a detailed characterization of their physical features during all the fabrication steps to have in the end a reliable technology. Moreover, the electrical performances of MEA silicon chips mounted on standardized connector boards via ultrasound wire-bonding have been tested using non-destructive electrochemical methods: linear sweep and cyclic voltammetry, impedance spectroscopy. Further, an experimental recording chamber package suitable for in vitro electrophysiology experiments has been realized using custom-design electronics for electrical stimulus delivery and local field potential recording, included in a complete electrophysiology setup, and the experimental structures have been tested on newborn rat hippocampal slices, yielding similar performance compared to commercially available MEA equipments.
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13
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Ko D, Lee C, Lee EJ, Lee SH, Jung KY. A dry and flexible electrode for continuous-EEG monitoring using silver balls based polydimethylsiloxane (PDMS). Biomed Eng Lett 2012. [DOI: 10.1007/s13534-012-0049-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Yazicioglu RF, Grundlehner B, Harpe P, Makinwa KAA, Van Hoof C. A 160 μW 8-Channel Active Electrode System for EEG Monitoring. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2011; 5:555-67. [PMID: 23852553 DOI: 10.1109/tbcas.2011.2170985] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
This paper presents an active electrode system for gel-free biopotential EEG signal acquisition. The system consists of front-end chopper amplifiers and a back-end common-mode feedback (CMFB) circuit. The front-end AC-coupled chopper amplifier employs input impedance boosting and digitally-assisted offset trimming. The former increases the input impedance of the active electrode to 2 GΩ at 1 Hz and the latter limits the chopping induced output ripple and residual offset to 2 mV and 20 mV, respectively. Thanks to chopper stabilization, the active electrode achieves 0.8 μVrms (0.5-100 Hz) input referred noise. The use of a back-end CMFB circuit further improves the CMRR of the active electrode readout to 82 dB at 50 Hz. Both front-end and back-end circuits are implemented in a 0.18 μm CMOS process and the total current consumption of an 8-channel readout system is 88 μA from 1.8 V supply. EEG measurements using the proposed active electrode system demonstrate its benefits compared to passive electrode systems, namely reduced sensitivity to cable motion artifacts and mains interference.
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Staudenmann D, Roeleveld K, Stegeman DF, van Dieën JH. Methodological aspects of SEMG recordings for force estimation--a tutorial and review. J Electromyogr Kinesiol 2009; 20:375-87. [PMID: 19758823 DOI: 10.1016/j.jelekin.2009.08.005] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 08/19/2009] [Accepted: 08/19/2009] [Indexed: 10/20/2022] Open
Abstract
Insight into the magnitude of muscle forces is important in biomechanics research, for example because muscle forces are the main determinants of joint loading. Unfortunately muscle forces cannot be calculated directly and can only be measured using invasive procedures. Therefore, estimates of muscle force based on surface EMG measurements are frequently used. This review discusses the problems associated with surface EMG in muscle force estimation and the solutions that novel methodological developments provide to this problem. First, some basic aspects of muscle activity and EMG are reviewed and related to EMG amplitude estimation. The main methodological issues in EMG amplitude estimation are precision and representativeness. Lack of precision arises directly from the stochastic nature of the EMG signal as the summation of a series of randomly occurring polyphasic motor unit potentials and the resulting random constructive and destructive (phase cancellation) superimpositions. Representativeness is an issue due the structural and functional heterogeneity of muscles. Novel methods, i.e. multi-channel monopolar EMG and high-pass filtering or whitening of conventional bipolar EMG allow substantially less variable estimates of the EMG amplitude and yield better estimates of muscle force by (1) reducing effects of phase cancellation, and (2) adequate representation of the heterogeneous activity of motor units within a muscle. With such methods, highly accurate predictions of force, even of the minute force fluctuations that occur during an isometric and isotonic contraction have been achieved. For dynamic contractions, EMG-based force estimates are confounded by the effects of muscle length and contraction velocity on force producing capacity. These contractions require EMG amplitude estimates to be combined with modeling of muscle contraction dynamics to achieve valid force predictions.
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Affiliation(s)
- Didier Staudenmann
- Department of Integrative Physiology, Neurophysiology of Movement Laboratory, University of Colorado, Boulder, CO, USA
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16
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Merritt C, Nagle H, Grant E. Fabric-Based Active Electrode Design and Fabrication for Health Monitoring Clothing. ACTA ACUST UNITED AC 2009; 13:274-80. [DOI: 10.1109/titb.2009.2012408] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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17
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Merletti R, Botter A, Troiano A, Merlo E, Minetto MA. Technology and instrumentation for detection and conditioning of the surface electromyographic signal: state of the art. Clin Biomech (Bristol, Avon) 2009; 24:122-34. [PMID: 19042063 DOI: 10.1016/j.clinbiomech.2008.08.006] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 08/20/2008] [Indexed: 02/07/2023]
Abstract
The aim of this review is to present the state of the art of the technology of detection and conditioning systems for surface electromyography (sEMG). The first part of the manuscript focuses on the sEMG electrode system technology: the electrode classification, impedance, noise, transfer function, the spatial filtering effect of surface electrode configurations, the effects of electrode geometry, and location on the recorded sEMG signal. Examples of experimental sEMG signals are provided to show the potential value of high-density sEMG electrode grids and multichannel amplifiers that allow to add spatial information to the temporal information content of the sEMG signal. Furthermore, the results of a simple simulation are reported, in order to emphasize the effects of the subcutaneous tissue layers and of the detection volume on the recorded sEMG signal. The second part of the manuscript focuses on the sEMG amplifier technology: the front end amplifier characteristics for signal conditioning, the methods for stimulation artifact reduction, filtering methods, safety requirements, and the methods for analog-to-digital conversion of the sEMG signal.
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Affiliation(s)
- Roberto Merletti
- Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics, Polytechnic of Turin, Corso Duca degli Abruzzi 24, 10129 Turin, Italy.
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Kang TH, Merritt CR, Grant E, Pourdeyhimi B, Nagle HT. Nonwoven Fabric Active Electrodes for Biopotential Measurement During Normal Daily Activity. IEEE Trans Biomed Eng 2008; 55:188-95. [DOI: 10.1109/tbme.2007.910678] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Degen T, Torrent S, Jäckel H. Low-noise two-wired buffer electrodes for bioelectric amplifiers. IEEE Trans Biomed Eng 2007; 54:1328-32. [PMID: 17605364 DOI: 10.1109/tbme.2006.889781] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Active buffer electrodes are known to improve the immunity of bioelectric recordings against power line interferences. A survey of published work reveals that buffer electrodes are almost exclusively designed using operational amplifiers (opamps). In this paper, we discuss the advantage of utilizing a single transistor instead. This allows for a simple electrode, which is small and requires only two wires. In addition, a single transistor adds considerably less noise when compared to an opamp with the same power consumption. We then discuss output resistance and gain as well as their respective effect on the common mode rejection ratio (CMRR). Finally, we demonstrate the use of two-wired buffer electrodes for a bioelectric amplifier.
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Affiliation(s)
- Thomas Degen
- Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology, Gloriasstrasse 32, Zurich 8001, Switzerland.
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Fonseca C, Silva Cunha JP, Martins RE, Ferreira VM, Marques de Sá JP, Barbosa MA, Martins da Silva A. A novel dry active electrode for EEG recording. IEEE Trans Biomed Eng 2007; 54:162-5. [PMID: 17260869 DOI: 10.1109/tbme.2006.884649] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The design and testing of a "dry" active electrode for electroencephalographic recording is described. A comparative study between the EEG signals recorded in human volunteers simultaneously with the classical Ag-AgCl and "dry" active electrodes was carried out and the reported preliminary results are consistent with a better performance of these devices over the conventional Ag-AgCl electrodes.
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Affiliation(s)
- C Fonseca
- INEB Instituto de Engenharia Biomédica, Laboratório de Biomateriais, Portugal.
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21
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Degen T, Jackel H. Preamplified two-wired active electrodes with DC-offset compensation. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2004:2251-4. [PMID: 17272175 DOI: 10.1109/iembs.2004.1403655] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Instrumentation amplifiers are widely used in biosignal measurements, due to their good common mode rejection ratio (CMRR) and their high input impedance. While the fabrication of active electrodes has been reported and their beneficial effects scientifically confirmed their usage in daily practice is still limited. This work describes a new instrumentation amplifier (IA) for biopotentials based on preamplified two-wired active electrodes with a gain of 40 dB. This is possible due to the DC-offset compensation provided by an integrator in the feedback loop. The DC-offset compensation allows for the first time to simultaneously measure the amplified signal and the DC-offset between the inputs. The signal quality is improved by amplifying and buffering the signal on the electrodes.
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Affiliation(s)
- Thomas Degen
- Department of Information Technology & Electrical Engineering, Swiss Federal Institute of Technology, Zürich, Switzerland
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22
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Manabe H. Evaluations of the ring shaped EMG measurement system. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2004:2188-91. [PMID: 17272159 DOI: 10.1109/iembs.2004.1403639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
This paper describes two evaluations of our previously proposed ring shaped EMG measurement system. The first evaluation, based on the collection of EMG by the system, shows that no statistically significant difference is seen between 3 EMG electrode configurations: the electrode is pressed with a finger, the electrode is fixed by tape, and a conventional plate electrode. The second evaluation suggests that our system has higher usability than the conventional electrodes. These results show that the ring shaped EMG measurement system is effective for measuring EMG, especially as part of the user interface for EMG-based applications.
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Affiliation(s)
- H Manabe
- Multimedia Laboratories, NTT DoCoMo, Kanagawa, Japan.
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23
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Degen T, Jäckel H. A pseudodifferential amplifier for bioelectric events with DC-offset compensation using two-wired amplifying electrodes. IEEE Trans Biomed Eng 2006; 53:300-10. [PMID: 16485759 DOI: 10.1109/tbme.2005.862531] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Most wired active electrodes reported so far have a gain of one and require at least three wires. This leads to stiff cables, large connectors and additional noise for the amplifier. The theoretical advantages of amplifying the signal on the electrodes right from the source has often been described, however, rarely implemented. This is because a difference in the gain of the electrodes due to component tolerances strongly limits the achievable common mode rejection ratio (CMRR). In this paper, we introduce an amplifier for bioelectric events where the major part of the amplification (40 dB) is achieved on the electrodes to minimize pick-up noise. The electrodes require only two wires of which one can be used for shielding, thus enabling smaller connecters and smoother cables. Saturation of the electrodes is prevented by a dc-offset cancelation scheme with an active range of +/- 250 mV. This error feedback simultaneously allows to measure the low frequency components down to dc. This enables the measurement of slow varying signals, e.g., the change of alertness or the depolarization before an epileptic seizure normally not visible in a standard electroencephalogram (EEG). The amplifier stage provides the necessary supply current for the electrodes and generates the error signal for the feedback loop. The amplifier generates a pseudodifferential signal where the amplified bioelectric event is present on one lead, but the common mode signal is present on both leads. Based on the pseudodifferential signal we were able to develop a new method to compensate for a difference in the gain of the active electrodes which is purely software based. The amplifier system is then characterized and the input referred noise as well as the CMRR are measured. For the prototype circuit the CMRR evaluated to 78 dB (without the driven-right-leg circuit). The applicability of the system is further demonstrated by the recording of an ECG.
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Affiliation(s)
- Thomas Degen
- Department of Information Technology and Electrical Engeering, Swiss Federal Institute of Technology, Zurich, Switzerland.
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24
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Staudenmann D, Kingma I, Stegeman DF, van Dieën JH. Towards optimal multi-channel EMG electrode configurations in muscle force estimation: a high density EMG study. J Electromyogr Kinesiol 2005; 15:1-11. [PMID: 15642649 DOI: 10.1016/j.jelekin.2004.06.008] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 06/02/2004] [Accepted: 06/29/2004] [Indexed: 10/26/2022] Open
Abstract
Surface EMG is an important tool in biomechanics, kinesiology and neurophysiology. In neurophysiology the concept of high-density EMG (HD-EMG), using two dimensional electrode grids, was developed for the measurement of spatiotemporal activation patterns of the underlying muscle and its motor units (MU). The aim of this paper was to determine, with the aid of a HD-EMG grid, the relative importance of a number of electrode sensor configurations for optimizing muscle force estimation. Sensor configurations are distinguished in two categories. The first category concerns dimensions: the size of a single electrode and the inter electrode distance (IED). The second category concerns the sensor's spatial distribution: the total area from which signals are obtained (collection surface) and the number of electrodes per cm(2) (collection density). Eleven subjects performed isometric arm extensions at three elbow angles and three contraction levels. Surface-EMG from the triceps brachii muscle and the external force at the wrist were measured. Compared to a single conventional bipolar electrode pair, the force estimation quality improved by about 30% when using HD-EMG. Among the sensor configurations, the collection surface alone appeared to be responsible for the major part of the EMG based force estimation quality by improving it with 25%.
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Affiliation(s)
- Didier Staudenmann
- Faculty of Human Movement Sciences, Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands
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25
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Chiou YH, Luh JJ, Chen SC, Lai JS, Kuo TS. The comparison of electromyographic pattern classifications with active and passive electrodes. Med Eng Phys 2004; 26:605-10. [PMID: 15271288 DOI: 10.1016/j.medengphy.2004.04.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2003] [Revised: 03/30/2004] [Accepted: 04/20/2004] [Indexed: 11/26/2022]
Abstract
Electromyographic (EMG) signals are usually acquired using surface electrodes, and they commonly serve as the control sources of myoelectric prosthetic limbs. The use of passive electrodes and amplifiers with adjustable gain is very popular in laboratories for the development of new control strategies. However, active electrodes without conductive jelly are used in most clinical applications of myoelectric hand control. There remains an important question: Are there any differences between using active and passive electrodes in EMG pattern classifications? Autoregressive and cepstral coefficients were used to evaluate recognition rates via both types of electrodes. The results showed that the estimated recognition rates in the passive electrodes were comparable to those in the active ones (averaged recognition rate, 88.5 vs. 85.84% in the autoregressive coefficients, and 84.84 vs. 83.5%, in the cepstral coefficients, respectively). Aside from the lack of significant statistical differences between them, the results imply that the differences between the recognition rates via these electrodes could be negligible. This would be helpful for the myoelectric control of assistive devices.
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Affiliation(s)
- Ying-Han Chiou
- Department of Electrical Engineering, National Taiwan University, Taiwan, People's Republic of China
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26
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Rupp R, Vossius G, Gerner HJ. [Bipolar , active electrode for 4-channel recording of dynamic surface EMG during electric stimulation]. BIOMED ENG-BIOMED TE 2003; 47 Suppl 1 Pt 2:609-10. [PMID: 12465252 DOI: 10.1515/bmte.2002.47.s1b.609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In this paper we present an electrode for measuring the surface electromyogram (EMG) that combines high quality of signal recording with the ease of use in clinical routine. Additional requirements have been the use of the electrode in combination with electrical stimulation and under dynamic conditions like walking. Special focus was put on the minimization of movement artifacts by integration of a dual impedance transformer (active electrode) and by a self-adjusting fixation of the two contacts of the electrode via proprietary springs. An elaborate preparation of the skin is not necessary due to a very high input impedance of the amplifier. A special circuit for overvoltage protection makes the electrode suitable for use in the presence of high voltage stimulation pulses without the risk of destroying the FET-input stages.
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Affiliation(s)
- R Rupp
- Stiftung Orthopädische Universitätsklinik Heidelberg, Deutschland.
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27
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Griss P, Tolvanen-Laakso HK, Meriläinen P, Stemme G. Characterization of micromachined spiked biopotential electrodes. IEEE Trans Biomed Eng 2002; 49:597-604. [PMID: 12046705 DOI: 10.1109/tbme.2002.1001974] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We present the characterization of dry spiked biopotential electrodes and test their suitability to be used in anesthesia monitoring systems based on the measurement of electroencephalographic signals. The spiked electrode consists of an array of microneedles penetrating the outer skin layers. We found a significant dependency of the electrode-skin-electrode impedance (ESEI) on the electrode size (i.e., the number of spikes) and the coating material of the spikes. Electrodes larger than 3 x 3 mm2 coated with Ag-AgCl have sufficiently low ESEI to be well suited for electroencephalograph (EEG) recordings. The maximum measured ESEI was 4.24 k(omega) and 87 k(omega), at 1 kHz and 0.6 Hz, respectively. The minimum ESEI was 0.65 k(omega) an 16 k(omega), at the same frequencies. The ESEI of spiked electrodes is stable over an extended period of time. The arithmetic mean of the generated dc offset voltage is 11.8 mV immediately after application on the skin and 9.8 mV after 20-30 min. A spectral study of the generated potential difference revealed that the ac part was unstable at frequencies below approximately 0.8 Hz. Thus, the signal does not interfere with a number of clinical applications using real-time EEG. Comparing raw EEG recordings of the spiked electrode with commercial Zipprep electrodes showed that both signals were similar. Due to the mechanical strength of the silicon microneedles and the fact that neither skin preparation nor electrolytic gel is required, use of the spiked electrode is convenient. The spiked electrode is very comfortable for the patient.
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Affiliation(s)
- Patrick Griss
- Department of Signals, Sensors and Systems, Royal Institute of Technology, Stockholm, Sweden.
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28
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Clancy EA, Morin EL, Merletti R. Sampling, noise-reduction and amplitude estimation issues in surface electromyography. J Electromyogr Kinesiol 2002; 12:1-16. [PMID: 11804807 DOI: 10.1016/s1050-6411(01)00033-5] [Citation(s) in RCA: 290] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
This paper reviews data acquisition and signal processing issues relative to producing an amplitude estimate of surface EMG. The paper covers two principle areas. First, methods for reducing noise, artefact and interference in recorded EMG are described. Wherever possible noise should be reduced at the source via appropriate skin preparation, and the use of well designed active electrodes and signal recording instrumentation. Despite these efforts, some noise will always accompany the desired signal, thus signal processing techniques for noise reduction (e.g. band-pass filtering, adaptive noise cancellation filters and filters based on the wavelet transform) are discussed. Second, methods for estimating the amplitude of the EMG are reviewed. Most advanced, high-fidelity methods consist of six sequential stages: noise rejection/filtering, whitening, multiple-channel combination, amplitude demodulation, smoothing and relinearization. Theoretical and experimental research related to each of the above topics is reviewed and the current recommended practices are described.
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Affiliation(s)
- E A Clancy
- Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609,
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29
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Lamontagne M. Application of Electromyography in Sport Medicine. REHABILITATION OF SPORTS INJURIES 2001:31-42. [DOI: 10.1007/978-3-662-04369-1_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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30
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Abstract
Alternatives to conventional wet electrode types are keenly sought for biomedical use and physiological research, especially when prolonged recording of biosignals is demanded. This paper describes a quantitative comparison of three types of bioelectrode (wet, dry and insulating) based on tests involving electrode impedance, static interference and motion artefact induced by various means. Data were collected simultaneously, and in the same physical environment for all electrode types. Results indicate that in many situations the performance of dry and insulating electrodes compares favourably with wet electrodes. The influence of non-stationary electric fields on shielded dry and insulating electrode types was compared to wet types. It was observed that interference experienced by dry and insulating electrode types was 40 dB and 34 dB less than that experienced by wet electrode types. Similarly, the effect of motion artefact on dry and insulating electrodes was compared to wet types. Artefact levels for dry and insulating electrodes were significantly higher than those for wet types at the beginning of trials conducted. By the end of the trial periods artefact levels for dry and insulating types were lower than wet electrodes by an average of 8.2 dB and 6.8 dB respectively. The reservations expressed in other studies regarding the viability of dry and insulating electrodes for reliable sensing of biosignals are not supported by the work described here.
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Affiliation(s)
- A Searle
- Department of Applied Physics, University of Technology, Sydney, Broadway, NSW, Australia
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31
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Bagwell PJ, Chappell PH. Real time microcontroller implementation of an adaptive myoelectric filter. Med Eng Phys 1995; 17:151-60. [PMID: 7735646 DOI: 10.1016/1350-4533(95)91888-n] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This paper describes a real time digital adaptive filter for processing myoelectric signals. The filter time constant is automatically selected by the adaptation algorithm, giving a significant improvement over linear filters for estimating the muscle force and controlling a prosthetic device. Interference from mains sources often produces problems for myoelectric processing, and so 50 Hz and all harmonic frequencies are reduced by an averaging filter and differential process. This makes practical electrode placement and contact less critical and time consuming. An economic real time implementation is essential for a prosthetic controller, and this is achieved using an Intel 80C196KC microcontroller.
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Affiliation(s)
- P J Bagwell
- Department of Electrical Engineering, University of Southampton, UK
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