A high accuracy voltage controlled current source for handheld bioimpedance measurement

2013 ◽  
Author(s):  
Dhouha Bouchaala ◽  
Qinghai Shi ◽  
Xinyue Chen ◽  
Olfa Kanoun ◽  
Nabil Derbel
Keyword(s):  
Current Source ◽  
High Accuracy ◽  
Bioimpedance Measurement

Development of a Multi-Function Virtual Instrument Based on a Constant Current Source

2013 ◽  
Vol 385-386 ◽  
pp. 492-495
Author(s):  
Dong Bing Dai ◽  
Ya Jun Wang ◽  
Ye Ping Sun ◽  
Zheng Guang Liu
Keyword(s):  
Data Acquisition ◽  
High Precision ◽  
High Power ◽  
Virtual Instrument ◽  
Current Source ◽  
High Accuracy ◽  
Constant Current ◽  
Constant Current Source ◽  
Data Acquisition Card ◽  
Further Development

Virtual instrument is a result of the computer combined with some instrument hardware, working for the instrumentation applications, it is one trend of the instrumentation development .This paper presents a design of a high-power and high-precision constant current source, studied three different electrical testing technologies based on constant current source and propose the principle of integrated the three electrical test technologies on a virtual instrument platform. A multi-function virtual instrument system based on LabView language, USB data acquisition card and a constant current source has been developed. This system has a high accuracy, high integration and a thecapability of further development etc..

scholarly journals Analysis, Simulation, and Development of a Low-Cost Fully Active-Electrode Bioimpedance Measurement Module

Technologies ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 59
Author(s):  
Christos Dimas ◽  
Vassilis Alimisis ◽  
Ioannis Georgakopoulos ◽  
Nikolaos Voudoukis ◽  
Nikolaos Uzunoglu ◽  
...  
Keyword(s):  
Low Cost ◽  
Current Source ◽  
Operational Amplifiers ◽  
Instrumentation Amplifier ◽  
Active Electrode ◽  
Fully Differential ◽  
Transient Simulations ◽  
Load Resistor ◽  
Complete Circuit ◽  
Bioimpedance Measurement

A low-cost 1 kHz–400 kHz operating frequency fully-active electrode bioimpedance measurement module, based on Howland current source, is presented in this paper. It includes a buffered positive feedback Howland current source, implemented with operational amplifiers, as well as an AD8421 instrumentation amplifier, for the differential voltage measurements. Each active electrode module can be connected to others, assembling a wearable active electrode module array. From this array, 2 electrodes can be selected to be driven from a THS413 fully differential amplifier, activating a mirrored Howland current source. This work performs a complete circuit analysis, verified with MATLAB and SPICE simulations of the current source’s transconductance and output impedance over the frequency range between 1 kHz and 1 MHz. Resistors’ tolerances, possible mismatches, and the operational amplifiers’ non-idealities are considered in both the analysis and simulations. A comparison study between four selected operational amplifiers (ADA4622, OPA2210, AD8034, and AD8672) is additionally performed. The module is also hardware-implemented and tested in the lab for all four operational amplifiers and the transconductance is measured for load resistors of 150 Ω, 660 Ω, and 1200 Ω. Measurements showed that, using the AD8034 operational amplifier, the current source’s transconductance remains constant for frequencies up to 400 KHz for a 150 Ω load and 250 kHz for a 1200 Ω load, while lower performance is achieved with the other 3 operational amplifiers. Finally, transient simulations and measurements are performed at the AD8421 output for bipolar measurements on the 3 aforementioned load resistor values.

scholarly journals A COMPARATIVE STUDY OF CURRENT SOURCES USED IN BIOIMPEDANCE MEASUREMENT SYSTEMS

2012 ◽  
pp. 87-90
Author(s):  
PADMA BATRA ◽  
RAJIV KAPOOR ◽  
RAJIV KAPOOR
Keyword(s):  
Comparative Analysis ◽  
Comparative Study ◽  
Bridge Circuit ◽  
Current Source ◽  
Bioelectrical Impedance ◽  
Impedance Tomography ◽  
Measurement Systems ◽  
Bioimpedance Measurement

The current source circuit is one of the most important parts in the bioelectrical impedance devices and Bio Impedance Tomography (BIT). There are many types of circuits like the Howland Current Source, Improved Howland Current Source, General Impedance Convertor, Wien Bridge circuit etc. This paper presents the comparative analysis of the available current sources and study of the best suited ones for the bioimpedance measurement and its various applications.

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

2014 ◽  
Vol 85 (5) ◽  
pp. 055111 ◽  
Author(s):  
Jinzhen Liu ◽  
Xiaoyan Qiao ◽  
Mengjun Wang ◽  
Weibo Zhang ◽  
Gang Li ◽  
...  
Keyword(s):  
Measurement System ◽  
Signal To Noise Ratio ◽  
Current Source ◽  
High Signal ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Bioimpedance Measurement

scholarly journals Design of current sources for load common mode optimization

2018 ◽  
Vol 9 (1) ◽  
pp. 59-71
Author(s):  
Vinicius G Sirtoli ◽  
Kaue F Morcelles ◽  
Volney C Vincence
Keyword(s):  
Voltage Drop ◽  
Current Source ◽  
Output Impedance ◽  
Output Current ◽  
Common Mode ◽  
Measurement Systems ◽  
Fully Differential ◽  
Common Mode Voltage ◽  
The Common ◽  
Bioimpedance Measurement

Abstract 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).

scholarly journals Optically isolated current source

2019 ◽  
Vol 6 (1) ◽  
pp. 18-21
Author(s):  
F. J. Pettersen ◽  
J. O. Høgetveit
Keyword(s):  
Current Source ◽  
Operational Amplifiers ◽  
Output Impedance ◽  
Output Current ◽  
Passive Components ◽  
Medical Settings ◽  
Spice Model ◽  
High Linearity ◽  
Small Load ◽  
Bioimpedance Measurement

Abstract There is a need for isolated current sources for use in selected bioimpedance measurement circuits. The requirement for good isolation is particularly important in medical settings because of safety concerns. A new circuit for producing voltage-controlled current is presented. Measurements have been made on a prototype and simulations have been done on a SPICE model. The presented circuit is an H-bridge where the output devices are the output photodiodes of high-linearity optocouplers. Five operational amplifiers, four high linearity optocouplers, and passive components are used. Output current capability is ±35 μA with an output impedance that is more than 1 M Ω. It is possible to achieve bandwidths above 1 MHz for small load impedances. This circuit is well suited for medical applications thanks to the isolation in the optocouplers.

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