Amplifier for testing current clamps

Napisana diplomska naloga je močno povezana z mojo trimesečno obvezno strokovno prakso, ki sem jo opravljal v sklopu svojega študijskega programa v podjetju Metrel d.d. Sedež podje-tja, ki se ukvarja z merilno in regulacijsko opremo, je v Horjulu. Mentor, ki sem ga imel v pod-jetju, je vodja kalibracijskega laboratorija. Kalibracijski laboratorij je akreditiran laboratorij in lahko izvaja različne kalibracije tako za Metrelove kot tudi za druge inštrumente. Diplomsko delo je vezano na eno od nalog, ki sem jo reševal med praktičnim usposabljanjem in kasneje zaključil. Opisuje izdelavo in meritve ojačevalnika, ki je namenjen kontroli različnih tokovnih klešč. Cilj naloge je bil sestaviti ojačevalnik, ki bi bil enostaven za uporabo in bi hkrati imel željeno natančnost in linearnost ojačenja. Z voltmetrom, priključenim na izhod ojačevalnika, preverja-mo natančnost meritev tokovnih klešč. V nalogi se posvečam tudi stabilnosti izhoda, saj je potrebno zagotoviti čim manjše nihanje meritev. Opisan je tudi postopek izdelave, saj je ojače-valnik rezultat mojega dolgotrajnega dela. Njegova izdelava in izboljšava sta bili odvisni od sprotnih zahtev in ugotovitev opravljenih meritev. Postopek dela se je začel z jasno določenimi zahtevami, ki jih je bilo potrebno izvesti za dose-go željenega rezultata. Ker je projekt služil podjetju Metrel, je zahteve določil mentor. Najprej sem zgradil preprosto vezje z operacijskim ojačevalnikom, ki sem ga ves čas izpopolnjeval in vsakič izvedel sklop meritev. Tako sem se približeval željenim zahtevam. Vse meritve sem be-ležil v Excelov dokument in iz njih nato izračunal željene podatke. V napisanem delu opisujem dva ojačevalnika. Prvi ojačevalnik sem moral opustiti, ker je bilo med uporabo kasneje ugotov-ljeno, da meritve majhnih tokov s tokovnimi kleščami niso zadovoljive. Meritve novega opera-cijskega ojačevalnika so pokazale, da so bile z novim ojačevalnikom odpravljene težave prej izdelanega ojačevalnika. Tako bo ojačevalnik primeren za uporabo v laboratoriju.This undergraduate thesis is closely linked to my three-month internship work in the company Metrel d.d, located in Horjul Slovenia. The company specializes in measuring and regulation equipment. During the internship, my mentor Janko Mole - Head of Calibration Laboratory assigned me a task. I\u27ve built an amplifier device to check the current clamps for quality. The project started by the design of the circuit. The amplifier circuit must accurately amplify the current from the current clamp\u27s output. To achieve the equirement to measure the current with the smallest value of 1 mA, the amplifier circuit should be able to amplify currents as small as 1 uA. After creating a simple amplifier circuit and taking its measurements, I started making changes and adding functionality to it. Finished circuit was later built in-to the casing. By measuring and comparing the input and output signals, I\u27ve inquired information that hel-ped me the amplifier analysis. The aim was to minimize the difference between a measured output signal and its expected value under 0,1 % for any current or frequency value of an in-put signal. During the measurements, it was crucial to find and eliminate all outside influences to get the right results from the measurements taken. After my three-month practice, I retur-ned to the company and built a new amplifier device, because of the problems that were fo-und while using the old one. Measurements of electric current of the smallest required value (1 mA) were not good enough. The new amplifier device has a different amplifier circuit which correctly amplifies the smallest currents. The main process were measurements, because of the importance for the understanding of the created circuit. All measurements were calculated in Excel. From there on, I analysed the re-sults by using tables and graphs. Improvements continued until results of the measured circuit proved that all the requirements were met