Dynamic Alarm Sensitivity Adjustment and Auto-Calibrating Smoke Detection

• US 20110018726A1
• Filed: 09/30/2010
• Published: 01/27/2011
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Universal Security Instruments Incorporated
• Original Assignee: Universal Security Instruments Incorporated
• Inventors: Gonzales, Eric V.
• Granted Patent: US 8,766,807 B2
• Time in Patent Office: Days
• US Class Current: 340/628
• CPC Class Codes: G08B 17/11 using an ionisation chamber for detecting smoke or gas
• CPC Class Codes: G08B 29/185 Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system
• CPC Class Codes: G08B 29/22 Provisions facilitating manual calibration, e.g. input or output provisions for testing; Holding of intermittent values to permit measurement

Abstract

A microprocessor controlled hazardous condition detection system containing a sensor package, the sensor package containing sensors exposed to the ambient environment. The system also includes an alarm means coupled to the sensor package through a microprocessor having volatile and non-volatile memory. The microprocessor includes a memory storage device containing a plurality of alarm thresholds stored therein. Each of the plurality of alarm thresholds is associated with a predetermined set of ionization levels in the ambient environment. The microprocessor receives periodic ionization readings from the sensor package, and conditions the received readings by removing a selected amount of noise and attenuation therefrom. The microprocessor accumulates the conditioned ionization readings, selects and employs an optimized alarm threshold from the plurality of stored alarm thresholds, based on a set of the accumulated ionization readings. Upon detecting ionization levels in the ambient environment greater than the ionization levels linked to the selected alarm threshold the microprocessor causes the alarm means to generate an alarm condition.

Claims

1. A microprocessor controlled hazardous condition detection system comprising:

a housing containing a sensor package, said sensor package containing sensors said sensors being exposed to the ambient environment and taking periodic readings of predetermined environmental conditions;

an alarm means coupled to said sensor package, disposed in said housing;

a microprocessor coupled to said alarm means and sensor package, said microprocessor having volatile and non-volatile memory, said non-volatile memory having an alarm differential value and a clean air default value stored therein;

wherein a default alarm threshold is determined by adding said differential value to said clean air default value;

wherein upon system power-up, said default air alarm threshold is loaded into said volatile memory;

said microprocessor receives periodic readings of predetermined environmental conditions from said sensor package, stores said periodic readings in said volatile memory, calculates the average of a plurality of said periodic readings and generates a new alarm threshold by shifting the default air alarm threshold loaded into said volatile memory by a value derived from the difference in the calculated average environmental reading and said clean air default value;

wherein upon detection of an ambient environmental condition outside of said alarm threshold stored in said volatile memory said microprocessor causes said alarm means to generate an alarm condition.

2. The system of claim 1, wherein said alarm differential value is stored in said non-volatile memory at the point of manufacture.

3. The system of claim 1, wherein said clean air default value is stored in said non-volatile memory at the point of manufacture.

4. The system of claim 1, wherein said sensor package comprises at least one sensor for detecting smoke.

5. The system of claim 4, wherein said at least one sensor for detecting smoke is an ionization type sensor.

6. The system of claim 5, wherein said sensor package further comprises at least one smoke sensor that is of the photoelectric type.

7. The system of claim 5, wherein said sensor package comprises at least one gas sensor.

8. The system of claim 5, wherein said microprocessor shifts the default air alarm threshold loaded into said volatile memory by a value greater than the difference in the calculated average environmental reading and said clean air default value to decrease system sensitivity.

9. A microprocessor controlled hazardous condition detection system comprising:

a housing containing a sensor package, said sensor package containing an ionization type smoke sensor, said smoke sensor being exposed to the ambient environment and taking periodic readings of the ionization level in the ambient environment;

an alarm means coupled to said sensor package, disposed in said housing;

a microprocessor having volatile and non-volatile memory coupled to said sensor package and said alarm means said non-volatile memory having an alarm differential value and a clean air default value stored therein;

wherein a default alarm threshold is determined by adding said differential value to said clean air default value;

wherein said microprocessor receives periodic readings of the ionization levels in the ambient environment from said sensor package, stores said periodic readings in said volatile memory, calculates an average of a plurality of said periodic readings over a predetermined period of time, and generates a new alarm threshold by shifting the default air alarm threshold loaded into said volatile memory by a value generated from the difference in the calculated average environmental reading and said clean air default value;

wherein upon detection of an ambient environmental condition outside of said alarm threshold stored in said volatile memory said microprocessor causes said alarm means to generate an alarm condition.

10. The system of claim 9 wherein said alarm means is coupled to said microprocessor through an ASIC sensitivity set pin, said microprocessor using said ASIC sensitivity set pin to synchronize microprocessor active and inactive periods with the active and inactive periods of said ASIC.