An improved immersible oxygen probe for molten metals has a gas permeable body including an immersion end and a support end adapted for being supported by a lance. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. in the event that the validation fails certain critical functions of the platform are inhibited to prevent fraudulent operation of the platform. Racks are coupled to the frame at the first side portion thereof.