The differential Howland current source with high signal to noise ratio for bioimpedance measurement system

The stability and signal to noise ratio (SNR) of the current source circuit are the important factors contributing to enhance the accuracy and sensitivity in bioimpedance measurement system. In this paper we propose a new differential Howland topology current source and evaluate its output character...

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Bibliographic Details
Published in:Review of scientific instruments 2014-05, Vol.85 (5), p.055111-055111
Main Authors: Liu, Jinzhen, Qiao, Xiaoyan, Wang, Mengjun, Zhang, Weibo, Li, Gang, Lin, Ling
Format: Article
Language:English
Subjects:
ACCURACY
Circuits
Current sources
Dielectric Spectroscopy - instrumentation
Dielectric Spectroscopy - methods
Electric Impedance
Electrical impedance
IMPEDANCE
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
INTERFERENCE
KHZ RANGE
MHZ RANGE
Noise measurement
Plethysmography, Impedance - instrumentation
Plethysmography, Impedance - methods
Scientific apparatus & instruments
SENSITIVITY
SIGNAL-TO-NOISE RATIO
STABILITY
TOMOGRAPHY
TOPOLOGY
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Summary:The stability and signal to noise ratio (SNR) of the current source circuit are the important factors contributing to enhance the accuracy and sensitivity in bioimpedance measurement system. In this paper we propose a new differential Howland topology current source and evaluate its output characters by simulation and actual measurement. The results include (1) the output current and impedance in high frequencies are stabilized after compensation methods. And the stability of output current in the differential current source circuit (DCSC) is 0.2%. (2) The output impedance of two current circuits below the frequency of 200 KHz is above 1 MΩ, and below 1 MHz the output impedance can arrive to 200 KΩ. Then in total the output impedance of the DCSC is higher than that of the Howland current source circuit (HCSC). (3) The SNR of the DCSC are 85.64 dB and 65 dB in the simulation and actual measurement with 10 KHz, which illustrates that the DCSC effectively eliminates the common mode interference. (4) The maximum load in the DCSC is twice as much as that of the HCSC. Lastly a two-dimensional phantom electrical impedance tomography is well reconstructed with the proposed HCSC. Therefore, the measured performance shows that the DCSC can significantly improve the output impedance, the stability, the maximum load, and the SNR of the measurement system.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4878255