Fluidic devices were once a staple of control systems in harsh environments such as nuclear power plants or satellites, until they were superseded by electronic systems whose performance and size were rapidly improving. Nevertheless, the simplicity, robustness and autonomy of fluidic devices remain attractive features in many fluids engineering applications. In this study, a microfluidic oscillator, with a main jet only 20 μm wide, is produced, instrumented and tested. Particular to this study is the use of temperature micro-sensors that were embedded inside the oscillator in order to perform non-intrusive measurements. In addition, air is used as a working fluid and is fed at high pressures so that the flow is choked at the inlet. The pulsation of the oscillators can reach frequencies of up to 9kHz and it was possible to measure the resulting fluctuations at different points inside the micro-channels. The sensors were able to detect harmonics at up to 50kHz. With this spatial and temporal information, it finally becomes possible to probe the inner dynamics of the micro-meter scale oscillator and to better understand phenomena such as high-frequency microjet switching under highly compressible flow conditions.