LAUSR

The aim of this study was to explore the use of a logarithmic amplifier to improve the spatial resolution of a low-cost Electrical Impedance Tomography (EIT) system. In an EIT system, the measured signal has a large dynamic range from µV to mV, leading to the requirement of high resolution ADC cards. Logarithmic amplifier reduces the dynamic range, by expanding lower values and compressing higher values, thereby improving the sensitivity and at the same time preventing signal from saturation. In addition, a low resolution ADC can be used, making the system cost effective. This work evaluated the performance of a logarithmic amplifier and a linear amplifier used for signal conditioning, in a low-cost EIT system. APPROACH Two EIT systems based on linear amplifier and logarithmic amplifier were designed. Phantom experiments were carried out with very small amounts of current injection. The signal-to-noise ratio (SNR), image quality, minimum detectable size and minimum detectable conductivity change were obtained. MAIN RESULTS Logarithmic amplifier based EIT system increased the average SNR by 4dB. It also showed improvement in the resolution (RES) and contrast-to-noise ratio (CNR) of the images. The minimum size detectable by the logarithmic amplifier based system was of radius 0.25 cm in a tank of radius 11cm and minimum change in conductivity detectable was 11 %. SIGNIFICANCE Logarithmic amplifier based signal conditioning is a promising technique for improving the spatial resolution a low-cost EIT system that has a low resolution ADC.