Air quality sensor

• US 9,857,301 B1
• Filed: 04/13/2015
• Issued: 01/02/2018
• Est. Priority Date: 04/14/2014
• Status: Active Grant

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Nourbakhsh, Illah, Schapiro, Joshua, Bartley, Chris, Taylor, Michael
• Primary Examiner(s): Barbee, Manuel L
• Application Number:
  US14/684,542
• Time in Patent Office: 995 Days
• CPC Class Codes: G01N 15/06 Investigating concentration of particle suspensions by weighing G01N5/00; investigating sedimentation of particle suspensions G01N15/04; investigating individual particles G01N15/10
• CPC Class Codes: G01N 15/075 by optical means
• CPC Class Codes: G01N 15/1429 Signal processing
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/0046 in gas, e.g. smoke
• CPC Class Codes: G01N 2015/1486 Counting the particles
• CPC Class Codes: G01N 33/0062 concerning the measuring method, e.g. intermittent, or the display, e.g. digital
• CPC Class Codes: G01N 33/007 Arrangements to check the analyser calibrating G01N33/0006

Abstract

Air quality sensor comprises an optical particle sensor and a programmable processor circuit. The optical particle sensor detects particles having a size of 10 microns or less in diameter in ambient air of the optical particle sensor. The programmable processor circuit continuously computes updated air quality measures for the ambient air using an estimation algorithm based on pulses in an output signal from the particle sensor over time, such as a cumulative particle density value and/or a cumulative particle weight value. The optical particle sensor may comprise a LED and accordingly detect particles based on reflection of light energy from the LED by particles in a chamber of the sensor.

Claims

1. An air quality sensor comprising:

an optical particle sensor for detecting particles having a size of 10 microns or less in diameter in ambient air of the optical particle sensor, wherein the optical particle sensor outputs an output signal;

wherein the optical particle sensor comprises a LED and detects particles based on reflection of light energy from the LED by particles in a chamber of the optical particle sensor; and

a programmable processor circuit in communication with the optical particle sensor that is programmed to continuously compute updated air quality measures for the ambient air using an estimation algorithm based on pulses in the output signal from the optical particle sensor over time;

wherein the programmable processor circuit computes the updated air quality measures by performing operations that comprise;

adjusting a current value of the air quality measure at a first rate proportional to a difference between the current value and a raw value from the optical particle sensor, scaled by a constant, when the raw value is non-zero; and

exponentially decaying the current value of the air quality measure toward zero at a second rate when the raw value is zero, wherein the second rate is less than the first rate.

2. The air quality sensor of claim 1, wherein the air quality measure comprises a particle density value.

3. The air quality sensor of claim 1, wherein the air quality measure comprises a particle weight value.

4. The air quality sensor of claim 1, wherein the output signal of the optical particle sensor has a duty cycle that is approximately proportional to the number of particles detected by the optical particle sensor.

5. The air quality sensor of claim 1, wherein the estimation algorithm comprises a combination of linear proportional transfer functions from sensor events to calibrated air quality values.

6. The air quality sensor of claim 5, wherein parameters of the estimation algorithm are calibrated by minimizing error relative to a reference particle detector.

7. The air quality sensor of claim 6, wherein the reference particle detector comprises a laser-based reference particle detector.

8. The air quality sensor of claim 1, further comprising a display in communication with the processor circuit that displays real-time and historical air quality measures computed by the processor circuit.

9. The air quality sensor of claim 8, wherein the display displays the real-time and historical air quality measures in separate views upon receiving a user display selection input.

10. The air quality sensor of claim 9, wherein the display comprises a touch screen display for receiving the user display selection inputs.

11. The air quality sensor of claim 9, wherein the display of the historical air quality measures comprises a graph of the air quality measure over a time period of one or more hours.

12. The air quality sensor of claim 1, further comprising a wireless transceiver circuit in communication with the processor circuit, wherein the wireless transceiver circuit is for wirelessly transmitting the air quality measures computed by the processor circuit to a remote server via an electronic data communication network.

13. A method of determining the quality of ambient air, comprising:

detecting particles having a size of 10 microns or less in diameter in ambient air with an optical particle sensor, wherein the optical particle sensor comprises a LED and detects particles based on reflection of light energy from the LED by particles in a chamber of the optical particle sensor, and wherein the optical particle sensor outputs an output signal; and

computing, by a programmable processor circuit that is in communication with the optical particle sensor, a continuously updated air quality measure for the ambient air using an estimation algorithm based on pulses in the output signal from the optical particle sensor over time;

wherein computing the continuously updated air quality measure comprises;

adjusting a current value of the air quality measure at a first rate proportional to a difference between the current value and a raw value from the optical particle sensor, scaled by a constant, when the raw value is non-zero; and

exponentially decaying the current value toward zero at a second rate when the raw value is zero, wherein the second rate is less than the first rate.

14. The method of claim 13, wherein the output signal of the optical particle sensor has a duty cycle that is approximately proportional to a number of particles detected by the optical particle sensor.

15. The method of claim 13, further comprising, prior to computing the air quality measures, calibrating parameters of the estimation algorithm by minimizing errors relative to a reference particle detector.

16. The method of claim 13, further comprising displaying, by a display that is in communication with the processor circuit, real-time and historical air quality measures computed by the processor circuit.

17. The method of claim 13, further comprising, wirelessly transmitting the computed air quality measures, by a wireless transceiver circuit that is in communication with the processor circuit, to a remote server via an electronic data communication network.

18. An air quality sensor comprising:

an optical particle sensor for detecting particles having a size of 10 microns or less in diameter in ambient air of the optical particle sensor;

wherein the optical particle sensor comprises a LED and detects particles based on reflection of light enemy from the LED by particles in a chamber of the optical particle sensor;

a programmable processor circuit in communication with the optical particle sensor for computing a continuously updated air quality measure for the ambient air based on an output signal from the optical particle sensor;

wherein the programmable processor circuit computes the continuously updated air quality measure by performing operations that comprise;

adjusting a current value of the air quality measure at a first rate proportional to a difference between the current value and a raw value from the optical particle sensor, scaled by a constant, when the raw value is non-zero; and

exponentially decaying the current value of the air quality measure toward zero at a second rate when the raw value is zero, wherein the second rate is less than the first rate;

a memory unit for storing the continuously updated air quality measures computed by the processor circuit; and

a display in communication with the processor circuit that displays real-time and historical air quality measures computed by the processor circuit and stored in the memory unit.

19. The air quality sensor of claim 18, wherein the display displays the real-time and historical air quality measures in separate views upon receiving a user display selection input.

20. The air quality sensor of claim 19, wherein the display comprises a touch screen display for receiving the user display selection inputs.

21. The air quality sensor of claim 19, further comprising a wireless transceiver circuit in communication with the processor circuit, wherein the wireless transceiver circuit is for wirelessly transmitting the air quality measures computed by the processor circuit to a remote server via an electronic data communication network.

22. A method of determining the quality of ambient air comprising:

detecting particles having a size of 10 microns or less in diameter in ambient air with an optical particle sensor, wherein the optical particle sensor comprises a LED and detects particles based on reflection of light energy from the LED by particles in a chamber of the optical, particle sensor;

computing, by a programmable processor circuit that is in communication with the optical particle sensor, continuously updated air quality measures for the ambient air based on an output signal from the optical particle sensor;

wherein computing the continuously updated air quality measures comprises;

adjusting a current value of the air quality measure at a first rate proportional to a difference between the current value and a raw value from the optical particle sensor, scaled by a constant, when the raw value is non-zero; and

exponentially decaying the current value toward zero at a second rate when the raw value is zero, wherein the second rate is less than the first rate;

storing, in a memory unit associated with the processor circuit, the continuously updated air quality measures computed by the processor circuit; and

visually displaying, on a display in communication with the processor circuit, real-time and historical air quality measures computed by the processor circuit and stored in the memory unit.

23. The method of claim 22, wherein displaying the real-time and historical air quality measures comprises displaying the real-time and historical air quality measures in separate views upon receiving a user display selection input.

24. The method of claim 23, wherein the display comprises a touchscreen interface, and where the method further comprises receiving the user display selection inputs via the touchscreen interface.

25. The method of claim 23, further comprising wireless transmitting, by a wireless transceiver circuit that is in communication with the processor circuit, the air quality measures computed by the processor circuit to a remote server via an electronic data communication network.