Abstract: In FIGS. 5 and 7, a temperature chamber 4 encloses a centrifugal-fan wheel 8 that is mounted concentric with a test ring 2 such that the fan's radially expelled air, indicated by arrows 12, flows across the ring in parallel with the test ring surfaces and is circulated via heating/cooling elements back to the fan inlet. The test ring includes guide holes 36 and electronic components 32 with terminals 34. It can be rotated via a pin wheel 22 with drive pins 24 that engage in guide holes 36 . A vertically mobile contact head 26 includes guide pins 28 and contact pins 42 that are connected with an external test instrument 51. Each time the ring is rotated a step, the contact head moves down to first engage guide pins 28 with the guide holes 36—thereby accurately aligning the contact pins 42 with the terminals 34—and, upon further down movement, connecting the contact pins 42 with terminals 34.