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Related Experiment Video

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Measurement of Bioelectric Current with a Vibrating Probe

Measurement of Bioelectric Current with a Vibrating Probe

Published on: January 4, 2011

Biocompatible, high precision, wideband, improved Howland current source with lead-lag compensation.

A S Tucker¹, R M Fox, R J Sadleir

¹J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, USA. aarontucker@ufl.edu

IEEE Transactions on Biomedical Circuits and Systems

|July 16, 2013

Summary

The Howland current pump offers precise alternating current delivery for bioelectrical applications. Optimized operational amplifier requirements ensure high precision and stable output impedance for critical uses like Electrical Impedance Tomography (EIT).

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Area of Science:

Bioelectrical engineering
Medical instrumentation
Electrical engineering

Background:

The Howland current pump is widely used for precise electrical current delivery.
Output impedance is a critical parameter limiting current precision in bioelectrical applications with varying loads.
High precision alternating current delivery is essential for advanced medical imaging techniques.

Purpose of the Study:

To define minimum operational amplifier requirements for achieving target precision over a wide bandwidth.
To explore compensation strategies for maintaining stability and high-frequency output impedance.
To develop and verify a stable current source for Electrical Impedance Tomography (EIT).

Main Methods:

Theoretical analysis of operational amplifier requirements for precision current sources.
Development of compensation strategies for high-frequency output impedance and stability.
SPICE modeling and physical implementation of a Howland current pump for EIT.

Main Results:

Identified minimum operational amplifier specifications for precise current delivery.
Demonstrated effective compensation techniques for stability without compromising high-frequency output impedance.
Achieved a stable output impedance of 3.3 MΩ up to 200 kHz, providing 80 dB precision for EIT.

Conclusions:

The designed Howland current pump meets the stringent precision requirements for EIT.
Measurement of output impedance requires careful consideration of theoretical limitations.
Optimized designs can achieve high precision and stable output impedance for bioelectrical applications.