Flame detection system and received light quantity measuring method

A received light quantity measuring method of a flame detection system comprising:

• periodically applying a drive pulse voltage to an electrode of an optical sensor in a first state in which the optical sensor configured to detect light emitted from a light source is shielded from the light source;
• detecting a discharge current of the optical sensor in the first state;
• detecting a discharge of the optical sensor based on the detected discharge current in the first state;
• calculating a discharge probability in the first state based on a number of times of the periodically applying of the drive pulse voltage in the first state and a number of times of the detected discharge of the optical sensor during the periodically applying of the drive pulse voltage in the first state;
• periodically applying the drive pulse voltage to the electrode of the optical sensor in a second state in which the optical sensor is not shielded from the light source;
• detecting the discharge current of the optical sensor in the second state;
• detecting the discharge of the optical sensor based on the detected discharge current in the second state;
• calculating a discharge probability in the second state based on a number of times of the periodically applying of the drive pulse voltage in the second state and a number of times of the detected discharge of the optical sensor during the periodically applying of the drive pulse voltage in the second state;
• and
• calculating a received light quantity received by the optical sensor in the second state based on
• a reference received light quantity received by the optical sensor,
• a reference pulse width of the drive pulse voltage,
• a known discharge probability of a regular discharge in the second state when a pulse width of the drive pulse voltage is the reference pulse width and the received light quantity received by the optical sensor is the reference received light quantity,
• a known discharge probability of an irregular discharge in the second state caused by a noise component other than a discharge occurring due to a photoelectric effect of the optical sensor,
• the calculated discharge probability in the first state, and
• the calculated discharge probability in the second state.