Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1998-10-01
2001-04-24
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S628000, C340S629000, C340S578000, C250S574000, C356S438000
Reexamination Certificate
active
06222456
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to ambient condition detectors. More particularly, the invention pertains to photoelectric-type smoke detectors with variable sample rates.
BACKGROUND OF THE INVENTION
Smoke detectors have been extensively used to provide warnings of potential or actual fire conditions in a region being monitored. Photoelectric-type smoke detectors sample the contents of a smoke chamber intermittently.
Known photoelectric detectors sample the smoke chamber at a first rate in a quiescent state. In the event that a smoke sample exceeds a preset threshold, the sample rate is increased. If the level of smoke exceeds a threshold for several additional samples, an alarm condition will be indicated.
While known detectors do provide a variable sample rate, it is only in response to the presence of a predetermined smoke density. It would be desirable to be able to vary the rate even for low levels of smoke density without requiring the excessive power that can be required to operate continuously at a relatively high sample rate. Preferably such added functionality could be achieved without any significant increase in either cost or manufacturing complexity.
SUMMARY OF THE INVENTION
A detector samples an ambient condition at a predetermined rate. Circuitry in the detector analyzes the sampled values as they are being received. If the values meet a predetermined profile, such as a profile of a developing fire, the sampling rate is increased.
In one aspect, the circuitry recognizes the presence of a predetermined profile based on processing samples from an ambient condition sensor. For example, if three amplitude values in a row consecutively increase, the sample rate can be increased. If four sampled amplitudes in a row consecutively increase, the sample rate can again be increased.
Recognizing a pre-established profile and increasing the sample rate in response thereto provides additional benefits. Other processing such as smoothing of the sampled values to eliminate uncorrelated noise or carrying out other forms of preliminary processing will be accelerated due to the increased sample rate.
Yet another benefit of the present apparatus and process is that the average power consumption of the respective detector is only increased when the likelihood of a condition to be detected has increased. In systems having large numbers of detectors, the ability to reduce average power or current is particularly advantageous.
In yet another aspect, other recognizable profiles which can be used to produce increased sample rates include increased gradient values of the sampled amplitudes or the value of an integral of the sampled amplitudes. An alternate way in which a sample rate modifying profile can be established is to incorporate a second, different sensor into the detector.
The output signal from the second sensor can be processed. If a selected profile is recognized, the sample rate of the primary sensor can be increased.
Hence, where a selected profile has been recognized, the sample rate will be increased. If the profile is no longer being recognized, perhaps due to changing ambient conditions, the sample rate can be returned to its quiescent value. As a result, average power consumption will be reduced.
In yet another aspect, a detector can include multiple sensors. These multiple sensors can include a fire sensor or a non-fire sensor as a second sensor. In the case of more than one fire sensor, the sampling rate would increase if more than one fire sensor is giving an indication of a fire condition. In the case of the non-fire sensor, the sampling rate of the fire sensor would not increase or would decrease if the non-fire sensor is giving an indication of a non-fire condition.
A particular detector could include a photo-electric, optical, type sensor and an ionization sensor. These are normally sampled at a 5 second rate. Methods of implementing variable sampling for this example are:
a. if either sensor senses a potential fire condition, then the sampling interval of both the optical sensor and the ionization sensor will be decreased to 2.5 seconds; or
b. if the optical sensor senses a potential fire condition, the sampling interval of the ionization sensor will be decreased to 2.5 seconds. This reverse situation results in decreasing the sampling interval of the optical sensor; or
c. if both sensors sense a fire condition, then the sampling interval of both sensors will be decreased to 2 seconds (Otherwise, the sampling intervals are unchanged); or
d. if neither sensor senses a potential fire condition, then the sampling interval will be increased to 7.5 seconds.
Alternately, the sampling rate could increase linearly with the level of indication of the sensed condition. For example the sample interval could be shortened from a 5 second interval, with no indication, to a 4 second interval with a mild indication, to a 3 second interval with a stronger indication. Finally, the interval can be reduced to a 2 second interval with a very strong indication.
The rate is alterable by downloading different values into the detectors from a common control unit. The common control unit may determine that other devices are sensing a condition and set the remainder of the system or certain other devices to increase their sampling rate.
In yet another aspect, where the sampled signal is processed or filtered, both the sampling rate and the processing can be altered in response to a recognized fire profile. For example, where a predetermined profile has been recognized:
a) the sampling rate can be increased, (and the interval decreased) and the type of filtering changed or the degree of filtering decreased—both promote a faster response; or
b) the sampling rate can be increased—to promote a faster response—without altering the type or degree of filtering—thereby providing more information and a greater discrimination of a developing ambient condition; or
c) where there are two sensors, if one sensor is responsive to nuisance or false alarm causing conditions, the sampling rate of both sensors could be increased along with increasing the filtering of one or both sensor outputs to minimize false alarms.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.
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paten
Hofsass Jeffery
La Anh
Pittway Corporation
Rockey Milnamow & Katz Ltd.
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