The Fourier and Z transforms are important subjects in communication and electronic engineering careers. Given the difficulties posed by the mathematics involved in these transforms, we perform an investigation with students from a Mexican university regarding the understanding achieved once they had successfully completed a course on these subjects. A ten-question test was used  for the investigation, in which a conceptual map was used for its design, according to the ideas of Richard Skemp about instrumental understanding and relational understanding. Non-structured interviews were also performed to deepen the students’ conceptions. The results show that the students achieve an instrumental learning but not a relational one, and it could be determined that their lack of relational understanding is because they only instrumentally learn the mathematical objects on which the construction of these transforms is based.

instrumental understanding, relational understanding, Fourier transform, Z-transform.