title: An amplitude-to-time conversion technique suitable for multichannel data acquisition and bioimpedance imaging.
abstract: In this paper we exploit the high timing resolution offered by microprocessors to develop an amplitude measurement approach that is convenient for high channel count portable sinusoidal recording systems such as the bioimpedance measurements used in impedance imaging. This approach reduces the number of components required per channel, reducing cost, size and power consumption compared to the traditional approaches. The setup uses two high performance comparators to convert amplitude difference to a timing difference. This is captured by a high speed microprocessor. A straightforward algorithm removes DC and timing offsets. We suggest three modes of operation: fast: less than one period of the input, normal: exactly one input period and high precision: multiple input periods. The mean signal-to-noise ratio was 40, 81, and 112.4 dB in fast, normal, and high precision mode respectively for a range of resistive loads.
authors.affiliation: Department of Biomedical Engineering, College of Electronics and Information, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701, Korea.
authors.forename: Jong Cheol
authors.initials: JC
authors.lastname: Baeg
authors.forename: Hun
authors.initials: H
authors.lastname: Wi
authors.forename: Tong In
authors.initials: TI
authors.lastname: Oh
authors.forename: Alistair Lee
authors.initials: AL
authors.lastname: McEwan
authors.forename: Eung Je
authors.initials: EJ
authors.lastname: Woo
mesh_terms: D000465:Algorithms; D000669:Amplifiers, Electronic; D002138:Calibration; D002462:Cell Membrane / Q000378:metabolism; D003952:Diagnostic Imaging; D017097:Electric Impedance; D004867:Equipment Design; D006801:Humans; D008838:Microcomputers; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D013382:Subtraction Technique; D014054:Tomography