black box vs instrument

black box

noun
  • A theoretical construct or device with known input and output characteristics but unknown method of operation. 

  • A flight recorder; the brightly colored cockpit voice recorders and flight data recorders in an aircraft designed to aid in determining the cause of an accident. 

  • A device used in phreaking that prevents the calling party from being billed for the call placed. 

  • A type of theater characterized by a lack of decoration or complex mechanisms. 

  • Any similar device on motor vehicles, such as rail event recorders and ship trip recorders. 

verb
  • To focus on the inputs and outputs without worrying about the internal complexity. 

instrument

noun
  • A tool, implement used for manipulation or measurement. 

  • A legal document, such as a contract, deed, trust, mortgage, power, indenture, or will. 

  • A device used to produce music. 

  • A means or agency for achieving an effect. 

  • A person used as a mere tool for achieving a goal. 

  • A measuring or displaying device. 

verb
  • To devise, conceive, cook up, plan. 

  • To perform upon an instrument; to prepare for an instrument. 

  • To apply measuring devices. 

How often have the words black box and instrument occurred in a corpus of books? (source: Google Ngram Viewer )