System and method for high-sensitivity sensor

• US 8,963,728 B2
• Filed: 07/22/2014
• Issued: 02/24/2015
• Est. Priority Date: 05/27/2004
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Kates, Lawrence
• Primary Examiner(s): HUNNINGS, TRAVIS R
• Application Number:
  US14/338,249
• Publication Number:
  US 20140333445A1
• Time in Patent Office: 217 Days
• Field of Search: 340/577, 340/627, 340/628
• US Class Current: 340/628
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 2110/50 Air quality properties
• CPC Class Codes: F24F 7/007 with forced flow using ducting systems F24F7/06
• CPC Class Codes: G01N 33/0006 Calibrating gas analysers
• CPC Class Codes: G01N 33/0065 using more than one threshold
• CPC Class Codes: G01N 33/0075 for multiple spatially distributed sensors, e.g. for environmental monitoring transmission systems for measured values G08C
• CPC Class Codes: G08B 1/08 using electric transmission ; transformation of alarm signals to electrical signals from a different medium, e.g. transmission of an electric alarm signal upon detection of an audible alarm signal
• CPC Class Codes: G08B 17/10 Actuation by presence of smoke or gases , e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/11 using an ionisation chamber for detecting smoke or gas
• CPC Class Codes: G08B 19/00 Alarms responsive to two or more different undesired or abnormal conditions, e.g. burglary and fire, abnormal temperature and abnormal rate of flow
• CPC Class Codes: G08B 21/182 Level alarms, e.g. alarms responsive to variables exceeding a threshold
• CPC Class Codes: G08B 25/007 Details of data content structure of message packets; data protocols
• CPC Class Codes: G08B 25/009 Signalling of the alarm condition to a substation whose identity is signalled to a central station, e.g. relaying alarm signals in order to extend communication range
• CPC Class Codes: G08B 25/10 using wireless transmission systems G08B25/009 takes precedence
• CPC Class Codes: G08B 27/005 with transmission via computer network
• CPC Class Codes: G08B 29/26 by updating and storing reference thresholds
• CPC Class Codes: H04B 1/401 for selecting or indicating operating mode
• CPC Class Codes: H04B 1/69 Spread spectrum techniques

Abstract

A sensor unit that includes at least one sensor configured to measure an ambient condition is described. The controller can be configured to receive instructions, to report a notice level when the controller determines that data measured by the at least one sensor fails a report threshold test corresponding to a report threshold value. The controller can also be configured to obtain a plurality of calibration measurements from the at least one sensor during a calibration period and to adjust the threshold based on the calibration measurements. The controller can be configured to compute a first threshold level corresponding to background noise and a second threshold level corresponding to sensor noise, and to compute the report threshold value from the second threshold. In one embodiment, the sensor unit adjusts one or more of the thresholds based on ambient temperature.

Claims

1. A wireless device comprising:

a smoke chamber;

an emitter that operates to emit electromagnetic radiation into the smoke chamber;

a sensor for sensing a scattered portion of the electromagnetic radiation;

a calibration module configured to;

determine a first threshold value by performing operations comprising;

taking a plurality of first measurements from the sensor while the emitter is not operating and during a period when smoke is expected to be substantially absent from the smoke chamber;

averaging the plurality of first measurements; and

storing the average of the plurality of first measurements as the first threshold value; and

determine a second threshold value by performing operations comprising;

taking a plurality of second measurements from the sensor while the emitter is operating and during a period when smoke is expected to be substantially absent from the smoke chamber;

averaging the plurality of second measurements; and

storing the average of the plurality of second measurements as the second threshold value; and

a notification module configured to;

obtain a first operating measurement from the sensor while the emitter is not operating and during a period when it is unknown whether smoke is present in the smoke chamber;

obtain a second operating measurement from the sensor while the emitter is operating and during a period when it is unknown whether smoke is present in the smoke chamber; and

communicate a notification based on the first and second operating measurements and the first and second threshold values.

2. The wireless device of claim 1, further comprising:

a temperature sensor configured to measure an ambient temperature; and

a controller configured to apply a correction factor to the first threshold value based on the ambient temperature measurement.

3. The wireless device of claim 1, further comprising:

a temperature sensor configured to measure an ambient temperature; and

a controller configured to apply a correction factor to the second threshold value based on the ambient temperature measurement.

4. The wireless device of claim 1, wherein the notification module is further configured to:

compare the second operating measurement to the first operating measurement;

determine whether the second operating measurement is greater than the first operating measurement; and

communicate an indication that a fault condition has occurred when it is determined that the second operating measurement is not greater than the first operating measurement.

5. The wireless device of claim 1, wherein the notification module is further configured to:

calculate a recomputed first threshold value based on the first operating measurement;

compare the first threshold value to the recomputed first threshold value; and

communicate an indication that a fault condition has occurred when it is determined that the recomputed first threshold value differs from the first threshold value by more than a certain error threshold.

6. The wireless device of claim 1, wherein the notification module is further configured to:

calculate a recomputed second threshold value based on the second operating measurement;

compare the second threshold value to the recomputed second threshold value; and

communicate an indication that a fault condition has occurred when it is determined that the recomputed second threshold value differs from the second threshold value by more than a certain error threshold.

7. The wireless device of claim 1, wherein:

the calibration module is further configured to determine a third threshold value as a function of the first and second threshold values; and

the notification module is further configured to communicate a smoke condition based on a comparison of the first and second operating measurements and the third threshold value.

8. The wireless device of claim 7, wherein the notification module is further configured to communicate the smoke condition further based on a rate of increase calculated from the first and second operating measurements.

9. The wireless device of claim 8, wherein the notification module is further configured to communicate the smoke condition further based on the relative difference between the first and second operating measurements and the third threshold value.

10. A method of operating a wireless device, the method comprising:

determining a first threshold value by performing operations comprising;

taking a plurality of first measurements from a sensor of the wireless device while an emitter of the wireless device is not operating and during a period when smoke is expected to be substantially absent from the smoke chamber, the emitter emitting electromagnetic radiation into a smoke chamber and the sensor sensing a scattered portion of the electromagnetic radiation;

averaging the plurality of first measurements; and

storing the average of the plurality of first measurements as the first threshold value; and

determining a second threshold value by performing operations comprising;

taking a plurality of second measurements from the sensor while the emitter is operating and during a period when smoke is expected to be substantially absent from the smoke chamber;

averaging the plurality of second measurements; and

storing the average of the plurality of second measurements as the second threshold value;

obtaining a first operating measurement from the sensor while the emitter is not operating and during a period when it is unknown whether smoke is present in the smoke chamber;

obtaining a second operating measurement from the sensor while the emitter is operating and during a period when it is unknown whether smoke is present in the smoke chamber; and

communicating a notification based on the first and second operating measurements and the first and second threshold values.

11. The method of operating a wireless device of claim 10, further comprising:

determining whether a dangerous condition exists based on the first and second operating measurements and the first and second threshold values; and

causing a gas shutoff valve to shut off a gas supply when it is determined that a dangerous condition exists.

12. The method of operating a wireless device of claim 10, wherein the plurality of first measurements and the plurality of second measurements are taken as part of a calibration sequence executed in response to the wireless device having powered up.

13. The method of operating a wireless device of claim 10, further comprising:

taking a plurality of operating measurements from the sensor; and

operating a fan of the wireless device between taking measurements of the plurality of operating measurements, the fan being arranged within the wireless device such that operation of the fan clears smoke from the smoke chamber.

14. The method of operating a wireless device of claim 13, further comprising operating the fan based on instructions wirelessly received by the wireless device.

15. The method of operating a wireless device of claim 10, further comprising:

taking a third operating measurement from the sensor while the emitter is operating; and

communicating a smoke condition when it is determined that the third operating measurement exceeds the second threshold value by a certain amount.

16. A wireless device comprising:

means for operating a sensing means of the wireless device to sense a scattered portion of electromagnetic radiation emitted into a smoke chamber by emitting means of the wireless device;

means for determining a first threshold value by performing operations comprising;

taking a plurality of first measurements with the sensing means while the emitting means is not operating;

averaging the plurality of first measurements; and

storing the average of the plurality of first measurements as the first threshold value; and

means for determining a second threshold value by performing operations comprising;

taking a plurality of second measurements with the sensing means while the emitting means is operating and during a period when smoke is expected to be substantially absent from the smoke chamber;

averaging the plurality of second measurements; and

storing the average of the plurality of second measurements as the second threshold value;

means for obtaining a first operating measurement from the sensing means while the emitting means is not operating;

means for obtaining a second operating measurement from the sensing means while the emitting means is operating; and

means for communicating a notification based on the first and second operating measurements and the first and second threshold values.

17. The wireless device of claim 16, further comprising means for causing the wireless device to determine a third threshold value as a function of the first and second threshold values.

18. The wireless device of claim 17, further comprising:

means for taking a third operating measurement from the sensing means while the emitting means is operating; and

means for communicating a smoke condition when it is determined that the third operating measurement exceeds the third threshold value by a certain amount.

19. The wireless device of claim 16, further comprising means for recalculating the second threshold value during operation of the wireless device.

20. The wireless device of claim 16, further means for adjusting a power level of the emitting means based on either or both of the first or second threshold values.