Technical term for a device that controls or regulates a system, such as in engineering or industrial contexts.
This controller keeps the temperature constant.
制御装置 is a more general term for control equipment or apparatus, while 制御器 often implies a specific controller unit or regulator.
Standard kanji spelling for a control device, using 器 (device/instrument).
Alternate spelling using 機 (machine); less common but seen in some technical contexts.
Compound of 制御 (control) and 器 (device/instrument). The alternate form 制御機 uses 機 (machine).