Patent Publication Number: US-2023146813-A1

Title: Compensator in a detector device

Description:
BACKGROUND 
     The subject matter disclosed herein generally relates to detector devices, and more particularly to a detector device including a compensator. 
     Photoelectric detector devices, such as smoke detectors, typically use a light source transmitted at an angle relative to a photo detector that prevents a sufficiently high level of light from being detected by the photo detector under nominal conditions. When smoke is present, smoke particles scatter the light from the light source and some portion of the light is detected by the photo detector. The signal level detected by the photo detector can vary due to a number of effects, such as environmental conditions, component variations, component age, and the like. 
     BRIEF DESCRIPTION 
     According to one embodiment, a detector device includes a light source disposed within a chamber, a sensor disposed within the chamber, a compensator circuit electrically coupled with the sensor, and a controller. The controller is operable to receive a sensor signal generated by the sensor, determine a compensation factor to adjust the sensor signal, generate a compensation offset signal based on the compensation factor, and output the compensation offset signal to the compensator circuit to produce a compensated sensor signal as an adjustment to the sensor signal. The controller is further operable to energize the light source, monitor the compensated sensor signal with respect to an alarm limit, and trigger an alarm event based on the compensated sensor signal exceeding the alarm limit. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the compensator circuit includes an amplification circuit operable to amplify a sensor output of the sensor as an amplified sensor signal and a summing circuit operable to sum the amplified sensor signal with the compensation offset signal to produce the compensated sensor signal. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the summing circuit is an analog circuit. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include an analog-to-digital converter operable to sample and quantize the compensated sensor signal as a digital value and a digital-to-analog converter operable to convert the compensation offset signal from a digital signal to an analog signal prior to summing at the summing circuit. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the sensor signal received at the controller is the amplified sensor signal as sampled and quantized through the analog-to-digital converter when the compensation offset signal has a zero offset value. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the controller is further operable to de-energize the light source, determine one or more error sources of the sensor signal with the light source de-energized, and determine the compensation factor as an adjustment needed to reach a target baseline clean air value based on the one or more error sources. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the controller is further operable to determine whether the compensated sensor signal has increased above a baseline value and increase the compensation offset signal until the compensated sensor signal is at or below the baseline value. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the controller is further operable to detect a hush request, increase the compensation offset signal until the compensated sensor signal is below the alarm limit responsive to the hush request, and reset the compensation offset signal after a predetermined period of time elapses from detection of the hush request. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the controller is further operable to monitor a temperature sensor to determine a current temperature value and determine the compensation factor based on the current temperature value and a temperature to compensation offset mapping. 
     In addition to one or more of the features described above or below, or as an alternative, further embodiments may include where the controller is further operable to track an average value of the compensated sensor signal over an extended time period and decrease the compensation offset signal based on the average value until the compensated sensor signal is at or below a long-term target value. 
     According to another embodiment, a method of operating a detector device includes receiving, at a controller of the detector device, a sensor signal generated by a sensor of the detector device, determining a compensation factor to adjust the sensor signal, generating a compensation offset signal based on the compensation factor, and outputting the compensation offset signal to a compensator circuit to produce a compensated sensor signal as an adjustment to the sensor signal. The method can also include monitoring the compensated sensor signal with respect to an alarm limit and triggering an alarm event based on the compensated sensor signal exceeding the alarm limit. 
     Technical effects of embodiments of the present disclosure include compensating a detector of a detector device to enhance detection capabilities. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, that the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG.  1    is a perspective view of an example of a detector device according to an embodiment; 
         FIG.  2    is an exploded view of the detector device of  FIG.  1    according to an embodiment; 
         FIG.  3    is a schematic diagram of a control system of a detector device according to an embodiment; 
         FIG.  4    is a circuit diagram of a compensator circuit of a detector device according to an embodiment; 
         FIG.  5    is a plot of compensation provided by a compensator circuit according to an embodiment; and 
         FIG.  6    is a process flow diagram of a method of operating a detector device using a compensator circuit according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     Referring now to  FIGS.  1 - 3   , an example of a detector device  20  is illustrated. The detector device  20  includes a housing assembly  22  having a first, upper housing portion  24  and a second, lower housing portion  26  that is removably connected to the first housing portion  24 . The detector device  20  further includes a control system  30  including at least one detector circuit  32  and at least one alarm circuit  34  described in more detail below with reference to  FIGS.  3  and  4   . When the first and second housing portions  24 ,  26  are connected, the first and second housing portions  24 ,  26  enclose the control system  30  and other components necessary to operation of the detector device  20 . As used herein, the terms “upper”, “lower”, and the like are in reference to the detector device  20  in use as it is mounted on a surface, such as a ceiling in a building for example. Therefore, the upper housing portion  24  is typically closer to the ceiling than the lower housing portion  26 , and the lower housing portion  26  is typically the portion of the detector device  20  that will face downward toward the floor of the building. In some embodiments, the detector device  20  may be mounted on a wall such that upper housing portion  24  is closer to the wall than the lower housing portion  26 , and the lower housing portion  26  is typically the portion of the device  20  that will face outward toward the interior space of the room or space to be monitored. 
     In the non-limiting embodiment of  FIG.  2   , the upper housing portion  24  includes a base plate  36  and a trim plate  38  disposed upwardly adjacent the base plate  36 . The trim plate  38  is typically positioned adjacent to or flush with a mounting surface, such as a ceiling or wall for example. As shown, both the trim plate  38  and the base plate  36  include a centrally located opening  40 ,  42  respectively, having a similar size and shape. In embodiments where the detector device  20  is “hardwired”, a power source  44  located within the mounting surface, such as an AC power supply, for example, may extend into the aligned openings  40 ,  42 . 
     A printed circuit board  46  is disposed generally between the base plate  36  and an adjacent surface of the lower housing portion  26 . The printed circuit board  46  includes the circuitry and/or components associated with the at least one detector circuit  32  and at least one alarm circuit  34 . In embodiments where the detector device  20  is “hardwired”, the printed circuit board  46  is directly connected to the power source  44 . In such embodiments, part of the printed circuit board  46  may extend into the central opening  40 ,  42  of the upper housing portion  24  to connect to the power source  44 . The printed circuit board  46  may be adapted to receive one or more batteries sufficient to provide power thereto to operate the detector device  20  for an extended period of time. The power provided by the batteries may be the sole source of power used to operate the detector device  20 , or alternatively, may be supplemental to the power source  44 , for example in the event of a failure or loss of power at the power source. 
     The detector device  20  can include a light transmission device  74 , such as a light pipe for example, positioned within the housing  22  generally between the printed circuit board  46  and the lower housing portion  26 . The light transmission device  74  can be a passive device formed from a clear or generally transparent plastic material and configured to diffuse and evenly distribute the light generated as an external indicator, such as a light emitting diode or other display element. 
     A sound generation mechanism  48  may be disposed between the printed circuit board  46  and the lower housing portion  26 . The sound generation mechanism  48  receives power from the printed circuit board  46  to generate a noise in response to detection of a condition. Coupled to the lower housing portion  26  is an actuatable mechanism  50 , such as a button. The actuatable mechanism  50  may be a button configured to perform one or more functions of the detector device  20  when actuated. Examples of operations performed via the actuatable mechanism  50  include, but are not limited to, a press to test function, an alarm “hush”, a low battery “hush”, and end of life “hush”, radio frequency enrollment of additional detector devices  20  such as in a detection system including a plurality of detector devices  20  configured to communicate with one another wirelessly, and to reset the detector device  20  once removed from its packaging, for example. 
     In the illustrated, non-limiting embodiment, the actuatable mechanism  50  is received within an opening formed in the lower housing portion  26 , and is operably coupled to a control system  30  of the printed circuit board  46 . Although the actuatable mechanism  50  is shown positioned at the center of the lower housing portion, embodiments where the actuatable mechanism  50  is located at another position are also within the scope of the disclosure. Further, it should be understood that in embodiments where the actuatable mechanism  50  performs multiple operations, there may be only a single actuatable mechanism  50  located on the detector device  20  and no other mechanism is required. Alternatively, the detector device  20  may include a plurality of actuatable mechanisms  50 , each being operable to perform a distinct function or the actuatable mechanism  50  may be divided to form a plurality of actuatable mechanisms. In embodiments where the detector device  20  includes a plurality of separate actuatable mechanisms  50 , the actuatable mechanisms  50  may be located at any location relative to the housing  22 . 
     With reference to  FIG.  3   , a schematic diagram of an example of a control system  30  of the detector device  20  of  FIGS.  1  and  2    is shown in more detail. The control system  30  includes a controller  60  operable to receive an input from the at least one detector circuit  32 , for example, from a chamber  62 . It should be understood that the detector device  20  may be adapted for detection of a variety of hazardous conditions, including but not limited to smoke, carbon monoxide, explosive gas, and heat, for example. Further, while the discussion herein refers to controller  60 , one skilled in the art will recognize that the functionality and intelligence associated with this element may be embodied in a microcontroller, a microprocessor, a digital signal processor (DSP), a programmable logic device (PLD), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other intelligent, programmable device with associated input/output interfaces, memory, and supporting circuitry. Therefore, the use of the term “controller” herein shall be construed to cover any of these structures. 
     The detector circuit  32  includes a sensor  64  operable to detect light from a light source  63  and conditioned by a compensator circuit  65  electrically coupled to the sensor  64  and controlled by controller  60 . The sensor  64  can be, for instance, a photo detector sensor. The controller  60  also receives an input from a user-actuated switch  66  input, for example, coupled to the actuatable mechanism  50 . The controller  60  can also receive inputs from a temperature sensor  67 , an ambient light sensor  80 , and/or other sensors (not depicted). The controller  60  utilizes the inputs from these components  64 ,  65 ,  66 ,  67 ,  80  to generate an output alarm condition when the sensed environmental conditions so dictate. An alarm circuit  34  is utilized to broadcast via the sound generation mechanism  48  an appropriate audible sound, depending on which condition has been detected. The alarm circuit  34  may include both tone and synthesized voice message generation capabilities, or may be a simple piezo-electric type device. The detector device  20  can also include a visual warning system  68  with an external indicator circuit  72  and an external indicator  70 . The external indicator  70  can be a light emitting diode or other display element used to externally convey status and alerts. It should be understood that the detector device  20  illustrated and described herein is intended as an example only and that a detector device  20  having any configuration and capability is contemplated herein. 
     In embodiments, the controller  60  energizes the light source  63  during normal operation, and the sensor  64 , which is physically offset from the light source  63  in the chamber  62 , detects light from the light source  63  as scattered by particles in the chamber  62 . The compensator circuit  65  can amplify the output of the sensor  64  and apply a compensation offset signal as further described herein. 
       FIG.  4    depicts an example of the compensator circuit  65  in greater detail. The compensator circuit  65  includes an amplification circuit  402  operable to amplify a sensor output  404  of the sensor  64  as an amplified sensor signal  406 . In the example of  FIG.  4   , the amplification circuit  402  includes a first stage amplifier  408  to provide an initial amplification to the sensor output  404  and a second stage amplifier  410  to further scale the sensor output  404  as the amplified sensor signal  406 , which may be optimized for a voltage range of an analog-to-digital (A/D) converter  412 , e.g., about 0 to 2.5 volt range. In some embodiments, the voltage range of the A/D converter  412  can be different, such as about 0 volts to 5 volts, about −5 volts to +5 volts, and other such ranges. The A/D converter  412  can be part of the controller  60  or external to the controller  60  of  FIG.  3   . The compensator circuit  65  also includes a summing circuit  414  operable to sum the amplified sensor signal  406  with a compensation offset signal  416  to produce the compensated sensor signal  418 . In the example of  FIG.  4   , the summing circuit  414  is an analog circuit with a summing amplifier  420  operable on analog versions of the amplified sensor signal  406  and the compensation offset signal  416 . The A/D converter  412  is operable to sample and quantize the compensated sensor signal  418  as a digital value. Notably, a single instance of the A/D converter  412  can detect an offset compensated or a non-offset compensated instance of a sensor signal from the sensor  64  based on the value of the compensation offset signal  416 . 
     A digital-to-analog (D/A) converter  422  is operable to convert the compensation offset signal  416  from a digital signal to an analog signal prior to summing at the summing circuit  414 . Similar to the A/D converter  412 , the D/A converter  422  can be part of the controller  60  or external to the controller  60  of  FIG.  3   . The compensation offset signal  416  generated by the controller  60  can adjust the amplified sensor signal  406  as the compensated sensor signal  418  prior to sampling by the A/D converter  412 . Performing signal adjustments external to the controller  60  and in an analog format can preserve the available range of the A/D converter  412  and enhance corrections beyond the levels possible with only digital adjustments, as described herein. By performing compensation in the analog domain prior to conversion to the digital domain, the range of detectable signals can be shifted down from a value that would otherwise saturate the A/D converter  412  upon conversion to the digital domain. For instance, if the A/D converter  412  saturates with an input value of 2.5 volts, any voltage level above 2.5 volts cannot be discerned. However, if compensation shifts a 2.7 volt signal down by 0.5 volts to 2.2 volts, values between 2.5-2.7 volts that would not otherwise be distinguishable (i.e., both appear as 2.5 volts at the controller  60  due to saturation of the A/D converter  412 ) become observable levels of 2.0-2.2 volts at the A/D converter  412 . 
       FIG.  5    illustrates an exemplary plot  500  of the compensation provided by the compensator circuit  65  of  FIGS.  3  and  4    according to an embodiment and is described in reference to  FIGS.  1 - 5   . The A/D converter  412  has a fixed A/D range  502  that can be expressed in volts or counts. A clean air value  504  can be tracked as a sampled value of a sensor signal from the sensor  64  as observed at the A/D converter  412  and may initially be equivalent to the amplified sensor signal  406  when the compensation offset signal  416  is inactive or has a zero offset value. A detection margin  506  represents a difference between an alarm limit  508  and the clean air value  504 . The alarm limit  508  represents a value that, when exceeded, triggers the alarm circuit  34  to broadcast an appropriate audible sound via the sound generation mechanism  48 . The maximum number of counts of the A/D converter  412  represents a saturation limit  510 , where voltages that exceed the saturation limit  510  cannot be accurately read beyond the A/D range  502 . A saturation margin  512  represents a difference between the saturation limit  510  and the clean air value  504  in the example of  FIG.  5   . 
     Over time, the clean air value  504  can drift higher due to various effects, such as light ingress, temperature, humidity, dust, and other factors which affect the capacity of sensor  64  to detect light from a light source  63 . As the clean air value  504  increases, the detection margin  506  is decreased if the alarm limit  508  remains fixed. There may be limited capacity to increase the alarm limit  508  before reaching the saturation limit  510 . As the clean air value  504  increases, the saturation margin  512  also decreases. The reduction in detection margin  506  may increase the risk of nuisance triggering of the alarm circuit  34  as a lesser amount of particles, such as smoke particles, is needed to push the sensor signal read by the A/D converter  412  above the alarm limit  508 . 
     When compensation is active  514 , the controller  60  generates a compensation offset signal  416  and outputs the compensation offset signal  416  through the D/A converter  422  as an analog signal to the summing circuit  414  of the compensator circuit  65 . The compensation offset signal  416  can be a negative offset to reduce the amplified sensor signal  406  at the summing circuit  414  or a positive offset to increase the amplified sensor signal  406  at the summing circuit  414 , producing the compensated sensor signal  418  as an adjustment to the sensor signal as sampled by the A/D converter  412 . The plot  500  illustrates how an uncompensated clean air value  516  can continue to increase absent compensation, while a compensated clean air value  518  can provide additional detection margin  506  and saturation margin  512  as compared to the uncompensated clean air value  516  by decreasing the uncompensated clean air value  516  before reaching the A/D converter  412 . Performing the compensation as an analog offset can effectively expand the range of offset signals that can be applied to the full range of the D/A converter  422  and the full range of the A/D converter  412 , rather than being limited to only the A/D range  502  of the A/D converter  412  as would be the case for a digital-only compensation. For example, if the D/A converter  422  supports a range of 0-2.5 volts and the A/D converter  412  supports a range of 0-2.5 volts, a maximum offset of 2.5 volts by the D/A converter  422  can shift a 4.9 volt signal at the A/D converter  412  down to 2.4 volts, thus making the signal observable without saturating the A/D converter  412 . It will be understood that various relationships can exist based on gain values and operative ranges of the A/D converter  412  and the D/A converter  422 . 
       FIG.  6    shows a process flow of a method  600  of operating the detector device  20  of  FIG.  1   , in accordance with an embodiment of the disclosure. The method  600  is described in reference to  FIGS.  1 - 6    and can include additional steps beyond those depicted in  FIG.  6   . 
     At block  602 , controller  60  receives a sensor signal generated by the sensor  64 . At block  604 , the controller  60  determines a compensation factor to adjust the sensor signal. The compensation factor can be set based on a number of conditions or modes of operation. For example, the compensation factor can adjust for manufacturing variations, ambient light, variations in the chamber  62 , circuit leakage in the printed circuit board  46 , temperature variations, electrical component variations, humidity, dust, and other factors as further described herein. At block  606 , controller  60  generates a compensation offset signal  416  based on the compensation factor. 
     At block  608 , controller  60  outputs the compensation offset signal  416  to the compensator circuit  65  to produce a compensated sensor signal  418  as an adjustment to the sensor signal. An amplification circuit  402  of the compensator circuit  65  is operable to amplify a sensor output  404  of the sensor  64  as an amplified sensor signal  406 . A summing circuit  414  of the compensator circuit  65  is operable to sum the amplified sensor signal  406  with the compensation offset signal  416  to produce the compensated sensor signal  418 . The A/D converter  412  is operable to sample and quantize the compensated sensor signal  418  as a digital value. The D/A converter  422  is operable to convert the compensation offset signal  416  from a digital signal to an analog signal prior to summing at the summing circuit  414 . The sensor signal received at the controller  60  can be the amplified sensor signal  406  as sampled and quantized through the A/D converter  412  when the compensation offset signal  416  has a zero offset value (e.g., no positive or negative offset adjustment). 
     At block  610 , controller  60  monitors the compensated sensor signal  418  with respect to an alarm limit  508 . During normal operation, controller  60  can periodically energize the light source  63  to support monitoring for increases in the compensated sensor signal  418  indicative of particles, such as smoke particles. The controller  60  can trigger an alarm event based on the compensated sensor signal  418  exceeding the alarm limit  508 . 
     As previously noted, the compensation described herein can adjust for a number of conditions using the compensator circuit  65 . The controller  60  can use the compensator circuit  65  to establish a consistent setting for a clean air value  504  in dark conditions of the chamber  62 . For example, the controller  60  can de-energize the light source  63 , determine one or more error sources included in a clean air value  504  of the sensor signal with the light source  63  de-energized, and determine the compensation factor as an adjustment needed to reach a target baseline clean air value based on the one or more error sources quantified from a combination of factors, such as printed circuit board leakage, component variations, light ingress, and the like. The clean air value  504  while the light source  63  is de-energized represents a starting value for comparison to the alarm limit  508  with detection margin  506 . In some embodiments, the ambient light sensor  80  can also be used, for instance, to establish an ambient light level external to the chamber  62  to further fine tune the correction factor. The compensation offset signal  416  can be adjusted through the D/A converter  422  (e.g., 1.5 volts+/−0.5 volts) until the compensated sensor signal  418  reaches a target baseline clean air value, e.g., 100 millivolts as the target baseline clean air value, for example. This can compensate for manufacturing differences in components of the chamber  62  and other components of the detector device  20  while at nominal temperature/humidity conditions. 
     The controller  60  can also adjust the compensation factor to null effects of light ingress. For example, the controller  60  can determine whether the compensated sensor signal  418  has increased above a baseline value, and increase the compensation offset signal  416  until the compensated sensor signal  418  is at or below the baseline value. As ambient light leaks into the chamber  62 , the clean air value  504  may increase as observed by the compensated sensor signal  418 . The baseline value of the clean air value  504  may have previously been tuned to a value, e.g. a value of 100 millivolts, using the compensator circuit  65 . Light ingress can be confirmed using the ambient light sensor  80  to observe light levels external to the chamber  62 . When the compensated sensor signal  418  drifts above 100 millivolts due to light ingress, the compensation offset signal  416  can be increased, which results in a decrease of the compensated sensor signal  418 . Incremental increases of the compensation offset signal  416  can continue until the compensated sensor signal  418  reaches a clean air value  504  of 100 millivolts in this example. 
     The controller  60  can also use the compensator circuit  65  to implement a hush feature to temporarily remove an alarm limit trip condition and silence the sound generation mechanism  48 . For example, the controller  60  can detect a hush request (e.g., through actuatable mechanism  50  and switch  66 ), increase the compensation offset signal  416  until the compensated sensor signal  418  is below the alarm limit  508  responsive to the hush request, and reset the compensation offset signal  416  after a predetermined period of time elapses from detection of the hush request. When the alarm circuit  34  triggers sound from the sound generation mechanism  48 , a user may determine that the inducing event has ended or is not a true emergency (e.g., a result of cooking food). Rather than adjusting the alarm limit  508  further upward in the A/D range  502  at risk of hitting the saturation limit  510 , the controller  60  uses the compensator circuit  65  to temporarily drive the compensated sensor signal  418  down below the alarm limit  508  by adjusting the compensation offset signal  416 . Prior to adjusting the compensation offset signal  416  for a hush event, the controller  60  can store a copy of the compensation offset signal  416 . After a pre-determined period of hush time has elapsed, e.g., fifteen minutes, the controller  60  can restore the compensation offset signal  416  with the previously saved value such that future alarm events will be triggered and other intermediate adjustments to the compensation offset signal  416  are not lost. 
     As another example, the controller  60  can monitor the temperature sensor  67  to determine a current temperature value. The controller  60  can determine the compensation factor based on the current temperature value and a temperature-to-compensation offset mapping. The temperature-to-compensation offset mapping can change a step size in compensation adjustments in the compensation offset signal  416  for higher or lower temperatures using, for example, a predetermined lookup table. The temperature to compensation offset mapping may be set up as absolute temperature based adjustments or relative adjustments depending upon a rate of temperature change versus time. 
     As a further example, the controller  60  can use the compensator circuit  65  to null effects of dust ingress into the chamber  62 . The controller  60  can track an average value of the compensated sensor signal  418  over an extended time period and decrease the compensation offset signal  416  based on the average value until the compensated sensor signal  418  is at or below a long-term target value. The long-term target value may be 100 millivolts as a clean air value, for example. If the dust ingress results in an average drop in the compensated sensor signal  418 , a decrease in the compensation offset signal  416  can be incrementally performed until the compensated sensor signal  418  increases back to the long-term target value. 
     As described above, embodiments can be in the form of processor-implemented processes and devices for practicing those processes, such as a processor. Embodiments can also be in the form of computer program code containing instructions embodied in tangible media, such as network cloud storage, SD cards, flash drives, floppy diskettes, CD ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes a device for practicing the embodiments. Embodiments can also be in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into an executed by a computer, the computer becomes an device for practicing the embodiments. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. 
     The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.