Patent Application
20090072737
Embodiments are generally related to sensor methods and systems. Embodiments are also related to ultraviolet flame sensor for detecting run-on condition.
Flame sensors are used to sense the presence or absence of a flame in a heater or burner, for example, or other apparatus. Flame detector systems are available to sense various attributes of a fire and to warn individuals when a fire is detected. For example, flame detector systems utilizing ultraviolet (“UV”) sensors are known. In the flame detector system, UV radiation emitted from the flames of a fire is detected by the detector's UV sensor. When a sufficient amount of UV radiation is detected, the flame detector system goes into alarm to warn individuals of the flame.
Typically, the UV sensor can be constructed of a sealed UV glass tube with a pair of electrodes and a reactive gas enclosed therein. A constant voltage is typically applied across the UV sensor in order to adequately sense UV radiation. In the presence of UV radiation of a certain wavelength (typically in the range of 100-300 nm), the sensor discharges the voltage to indicate detection of UV radiation. After the UV sensor discharges, the voltage across the sensor must be refreshed to allow the sensor to continue to detect UV radiation. Typically, once a UV sensor discharges, it is refreshed at a periodic interval.
The performance of the UV sensor is known to degrade over time. It can therefore be important to monitor the performance or “health” of the UV sensor to identify when performance of the sensor degrades. One mode of failure is the state where the current flow across the two electrodes occurs spontaneously without the presence of the ultraviolet light from the flame. In this case the sensing tube is indicating the presence of a flame when in fact no flame is present. This condition is commonly referred to in the industry as “run-on”. A drawback for flame detector tubes that use photoemission for a metal surface followed by a discharge is that the when the tubes degrade they can fail do to run-on. Run-on is the condition in which the tube keeps firing even after ultraviolet light is not present.
In an effort to address the foregoing difficulties, it is believed that additional electrodes that are sensitive to a breakdown condition can be utilized to detect run-on conditions.
The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is, therefore, one aspect of the present invention to provide for improved sensor methods and systems.
It is another aspect of the present invention to provide for improved ultra violet flame sensor for detecting run-on conditions.
The aforementioned aspects and other objectives and advantages can now be achieved as described herein. A UV flame sensor for detecting a run-on condition in a flame detector tube is disclosed. The sensor comprises a pair of secondary electrodes that are enclosed in a mesotube to form a breakdown chamber in order to detect run-on conditions. These secondary electrodes are exposed to UV through an aperture in a cathode plate and are energized continuously by a lower voltage. The mesotube is expected to breakdown when a run-on condition occurs of. The secondary electrodes can be placed in the same gas environment as the primary electrodes that may take different forms, shapes and locations.
Secondary electrodes can be placed into the mesotube that are not related to the normal function of the primary electrodes. The lower voltage can be applied to the secondary electrodes and current can be obtained from the breakdown when UV light is present. The secondary electrodes can be exposed to UV, which get discharged when run-on condition occurs. Another mode of operation is that the secondary electrodes not exposed to UV and the run-on condition can be determined by identifying the discharge when UV light is detected. The secondary electrodes are located at greater distance so does not discharge until hydrogen levels decrease to a ‘dead’ level.
The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the detailed description, serve to explain the embodiments disclosed herein.
The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.
Ultra-violet sensors do not actually come in contact with the flame in a burner as do flame rod electrodes. The Ultra violet flame sensor detects the ultraviolet light, radiated from a flame but is insensitive to other ranges of emitted light such as visible or infrared light. Referring to
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When the voltage potential drops far enough the conduction stops. This causes the voltage to rise again. If Ultraviolet light is still present from the flame the conduction process will start again when the voltage has risen far enough. This continual sequence results in a series of pulses emitted from the sensor 100 when the flame is present. This series of pulses is then detected as a flame present signal by the burner control. The mesotube 120 is expected to break down when run-on condition occurs. The secondary electrodes 140 can be placed in the same gas environment as the primary electrodes 130 that may take different forms, shapes and locations. The secondary electrodes 140 can be placed into the mesotube 120 that are not related to the normal function of the primary electrodes 130. The secondary electrodes 140 can be exposed to UV without discharging until run-on condition occurs. Another mode of operation is that the secondary electrodes 140 not exposed to UV and the run-on condition can be determined by identifying the discharge when UV light is detected. The secondary electrodes 140 are located at greater distance so does not discharge until hydrogen levels decrease to a ‘dead’ level.
It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
