Impedance measurements with second-order harmonic oscillator for testing food sterility

Author

Nihtianov, Stoyan N. ; Shterev, Georgi P. ; Petrov, Nikolay ; Meijer, Gerard C M

Author_Institution

Fac. of Inf. Technol. & Syst., Delft Univ. of Technol., Netherlands

Volume

50

Issue

4

fYear

2001

fDate

8/1/2001 12:00:00 AM

Firstpage

976

Lastpage

980

Abstract

In this paper, we present a simple interface circuit for measuring impedance based on a second-order harmonic oscillator. The circuit is intended for testing the sterility of aseptically packed food products, where it must measure the conductivity changes of the packaged food in a nondestructive way. The measured impedance is modeled as a low-ohmic resistor (representing the conductivity of the food) in series with a capacitor (the walls of the food container). The oscillator is built with fast current-feedback operational amplifiers (CFOA). To measure the resistive component of the impedance, an AC-to-DC converter is realized with a wide frequency range analog multiplier. The presented experimental results prove that with this interface circuit an accurate measurement of the impedance components can be achieved in a frequency range up to 10 MHz. The range of the resistive component is from a few ohms up to 200 ohms; the range of the capacitive component is from 50 pF up to 300 pF

Keywords

analogue multipliers; capacitors; electric impedance measurement; food processing industry; harmonic oscillators (circuits); operational amplifiers; resistors; spectral analysers; 10 MHz; 200 ohm; 50 to 300 pF; AC-to-DC converter; conductivity changes; current-feedback operational amplifiers; food container; food sterility; from 50 pF to 300 pF; impedance measurements; interface circuit; low-ohmic resistor; nondestructive measurement; packaged food; resistive component; second-order harmonic oscillator; up to 10 MHz; up to 200 ohms; wide frequency range analog multiplier; Capacitors; Circuit testing; Conductivity measurement; Food products; Frequency measurement; Impedance measurement; Nondestructive testing; Oscillators; Packaging; Resistors;

fLanguage

English

Journal_Title

Instrumentation and Measurement, IEEE Transactions on

Publisher

ieee

ISSN

0018-9456

Type

jour

DOI

10.1109/19.948310

Filename

948310