20.500.12556/RUL-171850 LOCK-IN OJAČEVALNIK LOCK-IN AMPLIFIER Pri merjenju električnih veličin v elektrotehniki pogosto naletimo na težave zaradi prisotnosti šuma, ki predstavlja naključne, nezaželene motnje v signalu. Tudi ob natančnem načrtovanju vezij in uporabi kakovostnih komponent popolna odprava šuma ni mogoča. Neizogibljiv bo vedno ostajal vsaj termični šum, ki izhaja iz toplotnega gibanja nosilcev naboja v materialih. Lock-in ojačevalnik je merilni inštrument, ki z uporabo metode fazno občutljivega zaznavanja (ang. PSD, phase-sensitive detection) omogoča izločanje šibkih signalov iz prevladujočega šuma. Sistem ob znani frekvenci iskanega signala omogoča natančne meritve signalov, ki bi jih z običajnimi tehnikami težko razbrali iz šuma. Cilj diplomske naloge je bil izdelati cenovno dostopen lock-in ojačevalnik za uporabo v okviru laboratorijskih vaj na Fakulteti ter na podlagi preizkusa predstaviti in ovrednotiti njegove zmogljivosti. Izdelava je zajemala risanje električne sheme, kjer smo kot osnovo vzeli rešitev, predstavljeno v članku [1], ter jo razširili z možnostjo meritve diferencialnih napetostnih signalov ter tokovnih signalov. Dodali smo možnost nastavljivega faznega zamika referenčnega signala. Po izbiri ustreznih komponent in ohišja je sledil načrt tiskanega vezja, spajkanje komponent ter končno testiranje in izvajanje meritev. Funkcionalnost lock-in ojačevalnika smo preverili s poskusom meritve nizke upornosti reda mΩ. Meritev smo izvedli z uporabo napetostnega delilnika z eno znano in eno neznano upornostjo. Uporabili smo diferencialno napetostno meritev. Rezultati so pokazali odstopanje od referenčnih vrednosti znotraj 2,5 %, kar je zadovoljivo za uporabo v pedagoške namene. Kljub višji končni ceni izdelka od prvotno predvidene smo uspeli izdelati funkcionalen, cenovno ugoden in uporabniku prijazen lock-in ojačevalnik, ki s svojo natančnostjo ustreza potrebam učnega okolja. When measuring electrical quantities in electrical engineering, we often encounter problems due to the presence of noise, which represents random and undesired disturbances in the signal. Even with highly engineered circuits and the use of quality components, complete elimination of noise is impossible. At the very least, thermal noise, which is caused by the thermal motion of charge carriers in materials, will always remain. A Lock-in amplifier is a measurement instrument that uses the method of phase-sensitive detection (PSD) to isolate weak signals from dominant noise. Provided the frequency of the target signal is known, the system enables accurate measurements of signals that would otherwise be difficult to distinguish using conventional techniques. The objective of this thesis was to build a cost-effective lock-in amplifier for use in laboratory practices at the Faculty and to present and evaluate its performance through testing. The development process included designing the electrical schematic, based on a circuit presented in the paper [1], which was expanded to support differential voltage signal and current signal measurements. We have added the option to adjust the phase shift of the reference signal. After selecting the appropriate components and the enclosure, we designed the PCB layout, followed by soldering, testing, and performing measurements. The functionality of the lock-in amplifier was verified through an experiment measuring a low resistance in the mΩ range. The measurement was performed using a voltage divider consisting of one known and one unknown resistance. A differential voltage measurement was used. The results showed a deviation from reference measurements within 2,5 %, which is acceptable for educational use. Despite the final cost being higher than initially planned, we succeeded in building a functional, affordable, and user-friendly lock-in amplifier that meets the accuracy requirements of an educational setting. elektrotehnika analogna vezja ojačevalnik lock-in fazno občutljivo zaznavanje PSD AD630 electrical engineering analog circuits amplifier lock-in phase-sensitive detection PSD AD630 true false false Slovenski jezik Angleški jezik Diplomsko delo/naloga 2025-09-03 12:05:00 2025-09-03 12:05:08 2025-09-22 04:05:15 0000-00-00 00:00:00 2025 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 62513 248281091 Perme_Lovro_-_LOCK-IN_OJACEVALNIK.pdf Perme_Lovro_-_LOCK-IN_OJACEVALNIK.pdf 1 FBF32D2DD9E5E9ABC07B078047577358 fe1c75036d367f009f92cf43c985451a73caedca553e4223a54775b0c681275e 563df44b-88ad-11f0-9328-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=215378 Fakulteta za elektrotehniko 0 0 0