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Figure 2
Simplified circuit diagram: 256 NTC sensors, each provided with a standard diode (1N4148) are placed on a 16 × 16 grid with rows and columns are chosen via four 8-channel multiplexers (MAX 4051). Addressing of the channels is accomplished by a PC controlled I/O-board (Quancom: PCI TTL-I/O 32), resulting signals are amplified (MAX 4166) and read in by an A/D-converter.