In this paper, the authors describe the main principle and methods of simple electromagnetic analysis and thus provide an overview of simple electromagnetic analysis. The paper describe specific SPA attack used visual inspection of EM traces, template based attack and collision attack. After reading the paper, the reader is sufficiently informed of any context of SEMA. This paper is the practical realization of SEMA which is focused on AES implementation. The visual inspection of EM trace of AES is performed step by step and the result is the determination of secret key hamming weight.