Flame detector having visible light related processing circuits and infrared related circuits respectively coupled to photodiodes to establish instantaneous dc related signal changes and peak-to-peak ac signals over a predetermined time interval

• US 9,449,485 B2
• Filed: 09/03/2014
• Issued: 09/20/2016
• Est. Priority Date: 09/03/2014
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Lapp, Theodore Raymond
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US14/476,094
• Publication Number:
  US 20160063831A1
• Time in Patent Office: 748 Days
• Field of Search: 250/554, 250/221, 250/205, 250/339.05, 250/339.14, 250/339.15, 340555-557
• US Class Current: 1/1
• CPC Class Codes: G01J 5/0802 Optical filters
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
• CPC Class Codes: G08B 29/188 Data fusion; cooperative systems, e.g. voting among different detectors

Abstract

A flame detector incorporates visible and near infrared sensors in common with processing circuits to form processed instantaneous, dc type, signal values minus an average value and peak-to-peak ranges of values of ac-type signals over a measurement time interval on the order of three seconds. The resulting values are further processed to determine the presence of a fire condition by comparing them to a predetermined threshold.

Claims

1. A flame detector comprising:

a first, visible light sensing photodiode;

visible light related processing circuits, coupled to the first photodiode to establish instantaneous dc related signal changes and peak-to-peak ac signals over a predetermined time interval;

a second, near infrared sensing photodiode;

infrared related processing circuits, coupled to the second photodiode to establish instantaneous dc related signal changes and peak-to-peak ac signals over a predetermined time interval; and

control circuits to determine the presence of a fire condition using amplitude components of the processed visible light and near infrared signals.

2. A detector as in claim 1 where a respective filter is associated with each photodetector.

3. A detector as in claim 1 where the visible light processing circuits and the near infrared processing circuits establish dc related signal values based on instantaneous signal values reduced by an average signal value.

4. A detector as in claim 1 where a range of established ac related values is based on a predetermined measurement time.

5. A detector as in claim 3 where a respective filter is associated with each photodiode.

6. A detector as in claim 5 where a range of established ac related values is based on a predetermined measurement time.

7. A detector as in claim 1 where additional circuits establish a measurement window for the presence of near infrared signals.

8. A detector as in claim 7 where additional circuits detect that the near infrared dc signal exceeds a predetermined threshold, and in response thereto, opens a window of a predetermined minimum length.

9. A detector as in claim 8 where a determination is made whether a processed near infrared ac signal exceeds a threshold based on a visible light related signal.

10. A detector as in claim 9 where a time interval that has passed since a most recent change in direction of the near infrared related signal is determined.

11. A method of operating a visible light sensor and a near infrared sensor to make a fire determination comprising:

providing a visual light sensor and a near infrared sensor;

processing selected amplitude values of signals received from the sensors;

establishing that an amplitude of a near infrared processed signal exceeds a predetermined threshold;

establishing a renewal window of a predetermined minimum duration; and

determining, using at least the processed amplitude values for both sensors, the presence of a fire.

12. A method as in claim 11 where processing includes forming instantaneous signal values reduced by an average value for each sensor.

13. A method as in claim 11 which includes forming ac peak-to-peak signal values over a predetermined measurement time interval.

14. A method as in claim 13 where processing includes forming instantaneous signal values reduced by an average value for each sensor.

15. A method as in claim 14 which includes comparing a timer count to a predetermined value, and responsive thereto, signaling the presence of a fire.