An instrumented cylinder is developed for simultaneous measurements of instantaneous focal heat transfer coefficients and dynamic behavior around a horizontal immersed tube in high-temperature fluidized beds. The cylinder contains one thin-him thermocouple probe and one capacitance probe. The oscillator of the capacitance probe is enclosed inside the cylinder, this arrangement ensuring a very stable noise-free output of the oscillator. Typical data obtained in a 160x230 mm cross-sectional high-temperature fluidized bed of 1.815 mm average diameter silica sand particles at 1034 degrees C are presented.