摘要: This paper presents the design and operation of an Eprom logic oscillator for an Electrical Impedance Tomography (EIT) imaging tool currently being used to image biological subjects at LLNL. Due to very low injection signal levels... 展开 This paper presents the design and operation of an Eprom logic oscillator for an Electrical Impedance Tomography (EIT) imaging tool currently being used to image biological subjects at LLNL. Due to very low injection signal levels and relatively high noise present in biological subjects, it is very important that an EIT imaging device (also known as an 'Impedance Camera') be designed to recover amplitude (and phase) information from a noisy received signal and that the noise generated by the system be minimized. The ability to detect small received signals masked by noise requires a comparison of the transmitted signal to the noisy received signal and precise timing to 'synchronize' these two signals. System noise can be reduced by synchronizing the application of the sinewave (to the subject) to the zero volt crossings of the transmitted sinewave. To address these demands, an Eprom oscillator was designed that not only generates an accurate 10khz to 50khz transmit sinewave, but, also, controls the switching of the sinewave (to coincide with its zero crossings), and generates accurately timed, adjustable, in-phase and quadrature, signals to assist in demodulating the noisy received signal. 2 refs., 7 figs. (ERA citation 13:043682) 收起