US Patent 7665415 Substrate processing apparatus

LEDs in an LED display part are arranged so as to have approximately the same placing form as containers. When a chemical solution in a container is exhausted, a corresponding LED of the LED display part lights up. Prior to an operation of replacing the container, an operator allows a bar code reader to read a bar code of an unused container. A bar code reader collator collates the bar code data of the unused container with the bar code data of a container corresponding to the lighting LED, which is already registered in a data base. When the bar code reader collator judges that the chemical solutions in the both containers are identical, the display of the LED is changed from a lighting-up display to a flashing display. This makes it easy to recognize the disposing position of the empty container to be replaced, thereby effectively preventing incorrect replacement of the container.