Interferometric observations at 10 micron combine the difficulties of the relatively new interferometric techniques with the problems of overcoming the strong and highly variable thermal background which are typical of thermal infrared observations. In particular, the detector subsystem must comply to strict requirements in terms of stability, of read noise, and of read out speed. Here we present the results obtained during laboratory test of MIDI, the Mid-IR interferometric instrument for VLTI. We selected as detector for the MIDI instrument a Raytheon 320x240 IBC array. We will discuss some of the aspects of the foreseen operation of MIDI, and the methods adopted to implement those on our detector system. We will show our results on detector stability, on its performances (in particular Quantum efficiency and read-out noise), and on the reaction to high fluxes. By using the possibility of hardware windowing, frame times of the order of 2 ms can be reached. Finally, we will show the characteristics of the detector when used in interferometric mode during tests of the whole MIDI instrument with both monochromatic and broad band calibration sources.