ELECTRICAL IMPEDANCE MEASUREMENT METHOD FOR PORTABLE ELECTRICAL IMPEDANCE IMAGING SYSTEM

摘要

An electrical impedance measurement device and method for a portable electrical impedance imaging system adopt a "current excitation and voltage measurement" principle. An excitation signal is a square wave current signal with constant strength. A response voltage signal on an imaging target passes through circuits such as a buffer amplification circuit, a resistor-capacitor direct current-blocking circuit, and a differential amplification circuit sequentially and is processed into a square signal with suitable amplitude, which is converted into a digital signal by an analog to digital converter at a suitable point of time. The ADC performs data sampling on a measured voltage signal at a high level and a low level of a square wave cycle, to obtain sampling results V 1 and V 2 , and the difference between the V 1 and V 2 is used as a voltage measurement result in this cycle. The average of voltage measurement results in a plurality of cycles is used as a final voltage measurement result. Due to the constant strength of the excitation current signal, the voltage measurement result can reflect electrical impedance information of the imaging target.