Which of the following best describes the measurement process in a pyrheliometer?

• A. Sunlight → window in pyrheliometer → thermopile → heat is converted to electrical signal → recorded
• B. Sunlight → window in pyrheliometer → heat is converted to electrical signal → thermopile → recorded
• C. Window in pyrheliometer → sunlight → thermopile → heat is converted to electrical signal → recorded
• D. Sunlight → heat is converted to electrical signal → window in pyrheliometer → thermopile → recorded