| 主权项 |
1. An impedance measurement system, comprising a control and detection circuit operatively connected to an unknown impedance to be measured, said control and detection circuit comprising a first AC signal generator for generating a first AC signal to be operatively applied to said unknown impedance and a first measurement circuit for measuring a current flowing into said unknown impedance, said control and detection circuit further comprising a reference impedance which is operably connectable in parallel to said unknown impedance by means of a switch,
wherein said control and detection circuit is configured for periodically connecting and disconnecting said reference impedance in parallel to said unknown impedance, thereby generating a modulated current measurement signal, wherein said control and detection circuit further comprises a transimpedance amplifier that receives at a first input the modulated current measurement signal indicative of the unknown impedance and the selectively paralleled reference impedance, and receives at a second input at an AC reference voltage, and is configured to transform the modulated current measurement into an AC measurement voltage at its output, wherein said control and detection circuit comprises a demodulation circuit configured to demodulate an amplitude of said AC measurement voltage indicative of said modulated current measurement signal, the amplitude of the AC measurement voltage corresponding to the demodulated current measurement signal being indicative of said reference impedance such that removing said amplitude of said AC measurement voltage from an amplitude of said reference AC voltage leaves remaining a DC voltage signal indicative of said unknown impedance. |
