An Instrumentation Amplifier as a Front-end for HP4284 Impedance Meter

Završni rad opisuje nekoliko različitih metoda mjerenja impedancije, usredotočeno na metodu autobalansirajuceg mosta. Uređajem temeljenom na spomenutoj metodi mjerena je impedancija poznatog iznosa na dva načina: izravno spajanjem na uređaj te instrumentacijskim pojačalom INA111 kao ulaznim sklopom. Impedancija poznatog iznosa zapravo predstavlja električni model ljudskog tkiva, stoga su u zadnjem poglavlju dani i rezultati mjerenja stvarnog tkiva podlaktice kao i mjerenje fizološke otopine. Rad u suštini pokazuje i usporeduje točnost opisanih načina mjerenja na frekvencijskom pojasu od 40Hz do 1MHz.This final paper describes several different measurement methods of electrical impedance, focusing on the method of an autobalancing bridge. The device based on this method, Hewlett-Packard 4284, measured impedance of the known amount in two ways: directly by connecting to the device with measuring electrodes and with INA111 instrumentation amplifier as a front-end. Impedance of the known amount is actually an electrical model of human tissue, therefore, in the last chapter, the results of measurement of real tissue of the lower arm are given. Saline solution impendance was also measured. The work essentially shows and compares the accuracy of the two described measurement methods on the frequency band from 40Hz to 1MHz