To prevent misassembly possible when diodes with different characteristics are handled on the same production line because of convenience of part supply though diodes with the same temperature characteristic should be used in temperature detection using diodes for detection temperature in a plurality of parts inside an ink jet printer.

In a non-volatile memory inside the printer, a correlation between ID information and a voltage for each of diodes having different temperature characteristics is held in a table form. In assembly of the printer, a diode ID to be used is written in the non-volatile memory by means of a switch 25. An actually detected voltage and a recorded output voltage under a room temperature are compared with each other in a comparison part 17. If they are different from each other, misassembly is determined.