For over a decade, the IES laboratory has been working in collaboration with the CEA on the development of acoustic instrumentation in the nuclear field. As part of this collaboration, the IES acoustics team is developing a miniaturized gas composition sensor for in situ measurements of gas composition in a fuel rod. The first experimental use of an acoustic sensor to measure gas composition dates back to 2010 with the REMORA 3 experiment, which estimated the release of fission gas in an experimental fuel rod. Unlike the sensor tested during REMORA 3, this new sensor should be able to operate at 300°C, a performance made possible by the use of a piezoelectric element based on bismuth titanate (NBT). The material is screen-printed onto an alumina substrate. The manufacturing process and initial characterization were presented in the previous version of ANIMMA 2021 [1]. In this article, we will focus on the performance of this type of sensor by characterizing different gas mixtures representative of the gases inside a fuel rod, in order to estimate relative deviations under laboratory conditions.