Flame detection system and received light quantity measuring method

Patent metadata

Field	Value
Publication number	US-11428575-B2
Application number	US-202016820034-A
Country	US
Kind code	B2
Filing date	Mar 16, 2020
Priority date	Mar 19, 2019
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

A flame detection system includes: an optical sensor that detects light generated from a light source; an applied voltage generating circuit that periodically applies a drive pulse voltage to the optical sensor, discharge determining portion that detects a discharge from the optical sensor, a discharge probability calculating portion that calculates a discharge probability based on a number of times of application of the drive pulse voltage and a number of times of discharge detected in the a first state in which the optical sensor is shielded from light and a second state in which the optical sensor can receive light, a sensitivity parameter storing portion storing known sensitivity parameters of the optical sensor; and a received light quantity calculating portion that calculates the received light quantity by the optical sensor in the second state based on the sensitivity parameters and the discharge probabilities calculated in the first and second states.

First claim

The invention claimed is:

1. A flame detection system comprising:
an optical sensor configured to detect light emitted from a light source;
an applied voltage generating portion configured to periodically apply a drive pulse voltage to an electrode of the optical sensor;
a current detecting portion configured to detect a discharge current of the optical sensor;
a discharge determining portion configured to detect a discharge of the optical sensor based on the discharge current detected by the current detecting portion;
a discharge probability calculating portion configured to calculate a discharge probability based on a number of times of application of the drive pulse voltage applied by the applied voltage generating portion and a number of times of discharge detected by the discharge determining portion during the application of the drive pulse voltage for each of a first state in which the optical sensor is shielded from the light source and a second state in which the optical sensor is not shielded from the light source;
a storing portion configured to store, in advance as known sensitivity parameters of the optical sensor,
a reference received light quantity received by the optical sensor,
a reference pulse width of the drive pulse voltage,
a 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, and
a 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; and

a received light quantity calculating portion configured to calculate the received light quantity received by the optical sensor in the second state based on
the sensitivity parameters stored in the storing portion,
the discharge probability calculated by the discharge probability calculating portion in the first state, and
the discharge probability calculated by the discharge probability calculating portion in the second state.

2. The flame detection system according to claim 1 , further comprising:
a light shield provided between the light source and the optical sensor; and
a shutter control unit configured to cause the light shield to perform an opening and closing operation to switch between the first state and the second state,

in which
the discharge probability calculating portion calculates the discharge probability based on the number of times of application of the drive pulse voltage by the applied voltage generating portion and the number of times of discharge detected by the discharge determining portion during the application of the drive pulse voltage respectively in the first state created by the light shield and the second state created by the light shield.

3. The flame detection system according to claim 1 , further comprising:
a received light quantity determining portion configured to determine a presence or an absence of light from the light source by comparing the received light quantity which is calculated by the received light quantity calculating portion with a received light quantity threshold value.

4. The flame detection system according to claim 1 , wherein
the received light quantity calculating portion is configured to calculate a received light quantity Q received by the optical sensor in the second state by

Q
=

Q
0

·

log

(

1
-

P

a
⁢
A

)

T

T
0

·

(

1
-

P

b
⁢
A

)

⁢

1
-
P

1
-

P
*

where
Q 0 is the reference received light quantity received by the optical sensor,
T 0 is the reference pulse width of the drive pulse voltage,
P aA is the discharge probability of the regular discharge,
P bA is the discharge probability of the irregular discharge,
P* is the discharge probability calculated by the discharge probability calculating portion in the first state,
P is the discharge probability calculated by the discharge probability calculating portion in the second state, and
T is the pulse width of the drive pulse voltage in the first and second states.

5. 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 p

Assignees

• Azbil Corp

Inventors

• Onuma Shun
• Mori Raita

Classifications

• G01J5/0805

  Means for chopping radiation · CPC title

• G01J5/00

  Radiation pyrometry, e.g. infrared or optical thermometry · CPC title

• G01J2001/444

  Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting · CPC title

• G01J5/0018 Primary

  Flames, plasma or welding · CPC title

• G01J2001/4466

  Avalanche · CPC title