Patent Abstract:
A device and method is provided for sensing or predicting when condensation having a given physical state is present or imminent and for suppressing such condensation from a surface, such as a vehicle windscreen, eyewear, goggles, helmet visor, computer monitor screen, window, electronic equipment, etc, by preventing or removing it. A first thermal sensor is in thermally conductive contact with the surface. A second thermal sensor is in an environment separated from the surface. A humidity sensor is in the environment of the second thermal sensor. A circuit causes a condensation suppression mechanism to be activated for preventing or removing condensation having the given physical state from the surface when a temperature sensed by the first thermal sensor, a temperature sensed by the second thermal sensor, and a humidity sensed by the humidity sensor indicate that a condensation condition is either present or imminent and requires prevention or removal at the surface.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part application of Patent Cooperation Treaty application PCT/US02/29422, filed Sep. 18, 2002, the entire disclosure of which is hereby incorporated herein by reference, which is a continuation of U.S. application Ser. No. 09/953,891, filed on Sep. 18, 2001, now U.S. Pat. No. 6,470,696, the entire disclosure of which is hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to devices and methods for sensing condensation conditions and for preventing or removing such condensation from surfaces such as vehicle windscreens, eyewear, goggles, helmet visors, computer monitor screen, windows, electronic equipment, etc., and especially devices and methods that use a thermal sensor and a humidity sensor in an adjacent ambient space with respect to the surface, or in thermally conductive contact with a thermoelectric cooler (TEC), for automatically and dynamically sensing condensation conditions when condensation appears on a surface or before such condensation actually appears on a surface. 
     BACKGROUND 
     The level of moisture in air at any time is commonly referred to as relative humidity. Percent relative humidity is the ratio of the actual partial pressure of steam in the air to the saturation pressure of steam at the same temperature. If the actual partial pressure of steam in the air equals the saturation pressure at any given temperature, the relative humidity is 100 percent. If the actual partial pressure is half that of the saturation pressure, the relative humidity is 50 percent, and so forth. 
     Dew point temperature, also known as condensation temperature or saturation temperature, is a function of the level of moisture or steam that is present in the air, and is the temperature at which air has a relative humidity of 100 percent. Condensation of moisture on a surface occurs when the temperature of that surface is at or below the dew point temperature of air surrounding the surface. 
     When air having a relatively high content of moisture comes into contact with a surface having a temperature at or below the dew point temperature, steam will begin to condense out of the air and deposit as water droplets onto the surface. At this time, a thin layer of liquid water comprised of small water droplets forms on the surface, creating a visual hindrance or “fog” to an observer looking at or through the surface. Once, formed, the condensation can be dispersed and removed either by raising the temperature of the surface, thereby changing the water into steam, or by lowering the relative humidity of the air surrounding the surface, thereby allowing the droplets to evaporate. 
     Steam, as a gas, exists in a saturated state at pressures and corresponding temperatures that are predictable and measurable. Notably, the standard for steam&#39;s thermodynamic properties, including saturation pressures and temperatures, in the United States and arguably the world, is the ASME (American Society of Mechanical Engineers) Steam Tables. These thermodynamic property tables are readily obtainable from ASME, as well as from engineering texts. 
     In that steam possesses certain characteristics and traits as a saturated gas that are measurable and exact, equations have been developed that permit the engineer to approximate and predict the properties of steam at a desired set of conditions when its properties are known at a different, or datum, set of conditions. Such an equation, in the case of gas saturation pressures and temperatures, is entitled the Clausius-Clapeyron Equation. This equation, which may be described in several variations, may be best stated for the purposes at hand in the following form:          ln              [       P   2                sat         P   1                sat         ]     =         Δ                 H     R     *     (       1     T   1       -     1     T   2         )                              
     where 
     P 1   sat  is the saturation partial pressure at state  1 , in units of psia; 
     P 2   sat  is the saturation partial pressure at state  2 , in units of psia; 
     ΔH is the heat of vaporization, equal to approximately 755,087.46 (ft−lbf)/lbm for steam; 
     R is the gas constant, equal to approximately 85.8 (ft−lbf)/(lbm−° R) for steam; 
     T 1  is the temperature at state  1 , in units of degrees Rankine; and 
     T 2  is the temperature at state  2 , in units of degrees Rankine. 
     Thus, using the Clausius-Clapeyron Equation, once steam &#39;s saturation pressure and temperature are known (the saturation pressure and temperature defining state  1  of the steam), given any other desired temperature, the saturation pressure at this temperature can be calculated to a high degree of accuracy (the temperature and calculated saturation pressure defining state  2  of the steam). Conversely, given any known state  1  conditions, for any desired saturated gas pressure, the saturation temperature can be calculated (the saturation pressure and calculated temperature defining state  2  of the steam). 
     SUMMARY 
     The invention provides a device and method for sensing or predicting when condensation is present or imminent and for suppressing such condensation from a surface by preventing it or removing it. A first thermal sensor is in thermally conductive contact with the surface. A second thermal sensor is in an environment separated from the surface. A humidity sensor is in the environment of the second thermal sensor. A circuit causes a condensation suppression mechanism to be activated for preventing or removing condensation having the given physical state from the surface when a temperature sensed by the first thermal sensor, a temperature sensed by the second thermal sensor, and a humidity sensed by the humidity sensor indicate that a condensation condition is either present or likely and requires prevention or removal at the surface. As used herein and in the claims, the term “suppress” encompasses prevention or preclusion of condensation conditions as well as, in the alternative, removal of existing condensation conditions. 
     The invention provides a convenient and practical mechanism for detecting condensation conditions quickly, before they manifest themselves on the surface. In certain embodiments the condensation suppression mechanism can be activated automatically when a condensation condition is detected, thereby providing convenience and safety where the surface is a windscreen of a vehicle, for example, or goggles, a helmet visor, computer monitor screen, window, electronic equipment enclosure. 
     In one embodiment of the invention, the second thermal sensor is in thermally conductive contact with a cooling device, and a circuit activates the cooling device in order to maintain the second thermal sensor at a temperature that is lower than a temperature of the first thermal sensor. The humidity sensor is in thermally conductive contact with the cooling device. The circuit causes the condensation suppression mechanism to be activated when the humidity sensor indicates a presence of high humidity conditions or condensation at the temperature that is lower than the temperature of the first thermal sensor. 
     In alternative embodiments of the invention, the environment of the second thermal sensor is in an adjacent ambient space with respect to the surface. The circuit determines that the condensation condition requires suppression at the surface by determining, from the temperature sensed by the second thermal sensor and the humidity sensed by the humidity sensor, the pressure of steam in the environment of the second thermal sensor. Then, the circuit may either determine a ratio of the pressure of steam in the environment of the second thermal sensor to the saturated steam pressure at the temperature sensed by the first thermal sensor, or determine a difference between a temperature sensed by the first thermal sensor and a dew point temperature associated with the pressure of steam in the environment of the second thermal sensor. 
     Thus, in certain embodiments of the invention, instead of measuring RH at an intentionally lowered temperature relative to the surface in question, RH (and temperature) can be measured in the surrounding ambient air adjacent to and in the proximity of the surface itself. Through calculation, the measurements taken in the surrounding ambient air can be extrapolated using the Clausius-Clapeyron Equation or any of its derivatives to determine whether condensation conditions exist on the surface in question or are imminent. Thus, it is not necessary physically to create a simulated (state  2 ) temperature in which a (state  2 ) relative humidity (RH) value can be measured. 
     Numerous additional features, objects, and advantages of the invention will become apparent from the following detailed description, drawings, and claims. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is a diagram of a surface in combination with a pair of thermal sensors in accordance with the invention. 
     FIG. 2 is a cross-sectional drawing of two options for incorporating a thermal sensor into a surface. 
     FIG. 3 is a cross-sectional drawing of thermoelectric cooler according to the invention in combination with a thermal sensor. 
     FIG. 4 is a block diagram of the electrical circuitry for an automatic sensing system according to the invention. 
     FIG. 5 is a block diagram of the electrical circuitry for two options of a condensation suppression system configured to be combined with the automatic sensing system of FIG.  4 . 
     FIG. 6 is a drawing of the thermoelectric cooler and thermal sensor of FIG. 3 within an air duct, the air duct being shown in partial cut-away view. 
     FIG. 7 is a flow diagram of a method for automatically sensing condensation conditions and for suppressing condensation from surfaces using the system illustrated in FIGS. 1-6. 
     FIG. 8 is a diagram of a surface in combination with a pair of thermal sensors and a humidity sensor in accordance with another embodiment of the invention 
     FIG. 9 is a cross-sectional drawing of two options for incorporating a thermal sensor into a surface. 
     FIG. 10 is a block diagram of electrical circuitry for automatic sensing systems according to the invention of the type shown in FIG.  8 . 
     FIG. 11 is a block diagram of the electrical circuitry for three embodiments of a condensation suppression system configured to be combined with the automatic sensing system of FIG.  10 . 
     FIG. 12 is a drawing of a condensation detection and suppression system, in accordance the invention, applied to a pair of goggles. 
     FIG. 13 is an exploded view of a portion of the electronic circuitry sensors juxtaposed relative to their protective hydrophobic cover as embodied in FIG.  12 . 
     FIG. 14 is a flow diagram of a method for automatically sensing condensation conditions and for suppressing such conditions from a surface using the system illustrated in FIGS.  10  and  11 . 
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     With reference to FIG. 1, an automatic sensing and condensation prevention and removal system according to the invention includes two thermal sensors  2  and  6 . Thermal sensor  2  is mechanically affixed to or embedded within a surface  1  from which condensation conditions are to be sensed and/or condensation is to be removed, such as a windscreen, goggles, a visor for a military helmet, pilot helmet, space-suit helmet, or other type of helmet, a computer monitor screen (such as a screen for a commercial electron beam or LCD computer monitor placed outdoors or in a high-humidity environment, such as in an industrial panel), a window or other transparent or translucent pane or enclosure (such as common windows in office buildings or enclosures that may house documents or other sensitive materials such as artwork and artifacts in museums or historic works), including plastics, an electronic equipment enclosure (such as a transparent or non-transparent enclosure for computer equipment, telecommunications equipment, etc. that might be placed outdoors or in high-humidity environments in which condensation might appear on the inside surface of the enclosure). 
     Each of the thermal sensors is a thermocouple formed by the thermal fusion of two dissimilar but electrically insulated metal conductors. In particular, the thermal fusion of metal conductors  3  and  4  forms thermal sensor  2  and the thermal fusion of metal conductors  3  and  7  forms thermal sensor  6 . Conductors  4  and  7  are of the same electro-conductive material and are of the same length. 
     If the temperatures of the bodies sensed by thermal sensors  2  and  6  are exactly the same, the thermocouple circuit through conductors  4  and  7  creates no electrical current. If the temperatures are not identical, a current is generated through this thermocouple circuit through conductors  4  and  7 , this current being proportional to the temperature difference of the two thermocouple junctions, as was first discovered by Thomas Seebeck in 1821. 
     The integrated sensing and condensation prevention and removal device creates an intentional temperature difference between thermocouples  2  and  6  by the thermoelectric cooling effect of a thermoelectric cooler (TEC) onto which thermocouple  6  is mechanically affixed. 
     With reference to FIG. 2, thermal sensor  2  may be mechanically affixed to surface  1  by an adhesive  5  (Option  1 ), or thermal sensor  2  may be embedded within surface  1  (Option  2 ). 
     With reference to FIG. 3, thermal sensor  6  is mechanically affixed by means of an adhesive  17  to the exterior face of the cold junction side  9  of thermoelectric cooler (TEC)  8 . The exterior face of the hot side  10  of TEC  8  may be mechanically bonded or otherwise attached to an optional heat sink  12 . A humidity sensor  13 , illustrated as a thin-film capacitive sensor but which may be any other sensing device that performs a similar function, is bonded by a mechanical bond  18  to thermocouple  6 . Thus, TEC cold-side face  9 , thermocouple  6 , and capacitive sensor  13  will always be at the same temperature. With reference to FIG. 6, TEC  8 , thermal sensor  6 , and thin-film capacitive sensor  13  are placed within the recirculation or outside air duct  58 , with heat sink  12  being attached to air duct  58 . 
     With reference to FIG. 4, as the above-mentioned intentionally-created temperature difference is created between thermocouples  2  and  6 , and, consequentially, as current is developed within the thermocouple circuit, the resultant voltage difference across conductors  4  and  7  is measured and amplified by voltage amplifier circuit  19 . This voltage signal is adjusted and offset for any impressed thermocouple effects due to any dissimilar metal junctions created by the connection of conductors  4  and  7  to voltage amplifier circuit  19  itself. The voltage signal is thereafter fed to TEC controller circuit  20 , within which the signal is compared to a pre-established differential voltage set point. Thereafter, TEC controller circuit  20 , supplied with an electrical power source and electrically grounded at ground  28 , electrically modulates a voltage that is applied to TEC  8  by conductors  14  and  15 , in order to maintain the cold face of TEC  8  at a temperature level that is a predetermined amount below the temperature of the windscreen, goggles, helmet visor, computer monitor screen, window, electronic equipment enclosure, or other surface. 
     The integrated sensing and condensation prevention and removal device is operated in a manner such that a constant difference is dynamically maintained between the temperature established at thermal sensor  6  by the action of TEC  8  and the temperature measured at the surface by thermal sensor  2 . Therefore, regardless of the temperature of the surface, the temperature established at the cold-side face of TEC  8  onto which thermal sensor  6  is affixed will always be lower than that of the surface by a predetermined amount. 
     Ambient air or outside air flows over thin-film capacitive sensor  13 . The capacitance of capacitive sensor  13  will be proportional to the relative humidity of the surrounding air. Because capacitive sensor  13  is maintained at a temperature less than that of the windscreen, goggles, helmet visor, computer monitor screen, window, electronic equipment enclosure, or other surface, the humidity level sensed will always be greater than that at the surface, and any liquid condensation will always form on capacitive sensor  13  before it forms on the surface. 
     Thin-film capacitive sensor  13  is connected by conductors  22  and  23  to capacitance-to-voltage circuit  29 . Conductor  23  and capacitance-to-voltage circuit  29  are connected to a common electrical ground  40 . Capacitance-to-voltage circuit  29  is supplied regulated 2.5-volt DC power by conductor  27  from voltage regulator circuit  26 , which is in turn energized by an electrical power source and an electrical ground  28 . Capacitance-to-voltage circuit  29  includes two #7556 timing integrated circuits  30  and  33 , resistors  34 ,  35 ,  37 , and  39 , and filter capacitors  31 ,  38 , and  41 . Timing integrated circuits  30  and  33  are electrically grounded at junctions  32 ,  36 ,  42 , and  44 . 
     Capacitance-to-voltage circuit  29  transforms the constant 2.5-volt DC supply voltage into a high-frequency AC signal. Thin-film capacitive sensor  13  is integrated into capacitance-to-voltage circuit  29  in a manner such that any capacitance of capacitive sensor  13  is transformed into a positive DC voltage relative to ground  44 , at conductor  43  of capacitance-to-voltage circuit  29 . The capacitance of capacitive sensor  13  increases as humidity increases, thereby resulting in an increased voltage at conductor  43 . The capacitance of capacitive sensor  13  is at a maximum when liquid moisture condenses onto capacitive sensor  13 . This condensation of liquid moisture onto capacitive sensor  13 , occurs when the temperature of capacitive sensor  13  is at or below the dew point of the ambient air. 
     With reference to FIG. 5, the output signal of the capacitance-to-voltage circuit is connected by conductors  45  and  46  to comparator circuit  47 . This output signal is compared to a set point voltage previously established in comparator circuit 47. If the signal is less than a pre-established set point, the signal is interpreted as meaning that fogging of the surface is not present or imminent. If the signal is equal to or greater to the pre-established set point, the signal is interpreted as meaning that fogging of the surface is present, imminent or likely to occur, in which case the system activates condensation suppression action. 
     If the signal from the capacitance-to-voltage circuit is equal to or greater than the pre-established set point, an electrical signal is directed to switching circuit  50  through conductors  48  and  49 , thereby causing the internal electronic or mechanical contactors of switching circuit  50  to close. Thereafter, electrical power is directed from switching circuit  50  through conductor  51 , which branches into conductors  53  and  54 . Conductor  53  is connected to a single-speed or multiple-speed fan  55  located within duct  58 . When fan  55  is energized, it rotates or increases its speed in order to generate or increase the volume of airflow directed toward the windscreen, goggles, computer monitor screen, window, electronic equipment enclosure, or other surface. The TEC, the thermal sensor mechanically bonded thereto, and the capacitive sensor are positioned within duct  58  upstream of fan  55 . 
     FIG. 5 illustrates a first option (Option  1 ), according to which electrical power is applied by conductor  54  to electrical heating coil  57 . Both fan  55  and heating coil  57  are electrically grounded by grounds  56  and  59  respectively. Energization of heating coil  57  raises the temperature of the air flowing over the heating coil element and thereafter flowing to and onto the face of the surface, thereby raising the temperature of the surface and the ambient space surrounding it so as to preclude condensation, or alternately if condensation is present, vaporizing water droplets deposited thereon. 
     According to a second option (Option 2), electrical power is applied by conductor  54  to an electric motor or solenoid actuator  60 , which is electrically grounded by ground  61 . Electric motor or solenoid actuator  60  is connected by linkage arm  63  to damper  62 , which moves as indicated in FIG. 5 so as to divert the airstream to an adjacent but interconnecting and parallel duct  65  within which a heater core  64  is mounted. Heater core  64  raises the temperature of the airstream passing through parallel duct  65 . Thereafter, the heated air is directed toward and onto the face of the surface, thereby raising the temperature of the surface and the ambient space surrounding it so as to preclude condensation, or alternately if condensation is present, vaporizing water droplets deposited thereon. 
     As a further option, the hot side face of the TEC may be used to provide heat, in lieu of the heating coil  57  or heater core  64 , to the air flowing toward and onto the face of the surface, thereby precluding condensation, or alternatively if condensation is present, vaporizing water droplets deposited thereon. 
     As yet a further option, since there will not be any ductwork per se in a helmet or goggles, or within certain other equipment having surfaces to be defogged, fan  55 , heating coil  57  and heater core  64  may be replaced by a heating coil embedded in or on the visor, etc., as micro-fine electro-resistive wires, or by an infrared source positioned so as to radiate onto the surface. 
     With reference to FIG. 7, once the automatic sensing and condensation prevention and removal system is powered up, the difference in temperature between the windscreen, goggles, helmet visor, computer monitor screen, window, electronic equipment enclosure, or other surface and the TEC is monitored to determine whether it is lower than a pre-established set point, and the TEC is energized to the extent necessary-to raise the difference to the set point. Also, the capacitive sensor is monitored to determine whether it indicates the presence of condensation. If the capacitive sensor indicates the presence of condensation a fan is energized, and either a heating coil or a damper actuator is activated. 
     With reference to FIG. 8, an alternative embodiment of an automatic sensing and condensation preclusion and removal system according to the invention includes two thermal sensors  68  and  71 . Thermal sensor  68  is mechanically affixed to or embedded within surface  66 , for which condensation conditions are to be monitored and/or from which condensate liquid is to be removed. Surface  66  can be, for example, a windscreen for a vehicle, a visor for a military helmet, pilot helmet, space-suit helmet, or other type of helmet, a visor for safety or non-safety apparatus, goggles, glasses, or other type of visor or goggle, a full-face air purifying respirator mask, a self-contained breathing apparatus (SCBA) mask, or other type of respirator mask, a computer monitor screen (such as a screen for a commercial electron beam or LCD computer monitor placed outdoors, in a cool or cold environment or in a high-humidity environment, such as in an industrial panel), a window or other transparent or translucent pane or enclosure (such as common windows in office buildings or enclosures that may house documents or other sensitive materials such as artwork and artifacts in museums or historic works), including plastics, an electronic equipment enclosure (such as a transparent or non-transparent enclosure for computer equipment, telecommunication equipment, cameras, projection equipment, transmitters, receivers, transceivers, or like components or objects that may be placed outdoors or in cool or cold environments or in high-humidity environments in which condensation might appear), optical equipment such as telescopes, binoculars, instrument bezels, viewing windows, eyeglasses and prescription lenses, electronic circuitry and circuit boards, and like components. 
     As schematically shown, the sensors may each be a thermocouple, formed by the fusion of two dissimilar metal conductors, a resistance temperature detector (RTD), a thermistor, or any electronic thermal measurement device performing the same function. Thermal sensor  68  is electrically connected to conductors  69  and  70 , while thermal sensor  71 , positioned adjacent to and in close proximity to surface  66 , at distance  72 , in the ambient surroundings  67 , is electrically connected to conductors  73  and  74 . Additionally, a humidity sensor  75 , illustrated as a thin-film capacitive relative humidity sensor, but which may be any other sensing device that performs a similar function is positioned immediately adjacent to thermal sensor  71 , but also may be mechanically affixed to or otherwise mechanically attached to thermal sensor  71 , it also being in close proximity to surface  66 , at distance  72 , in the ambient surroundings  67 . Capacitive sensor  75  is electrically connected to conductors  76  and  77 . 
     With reference to FIG. 9, thermal sensor  68  may be mechanically affixed to surface  66  by means of adhesive  78  (Option  1 ), or thermal sensor  68  may be imbedded within surface  66  (Option  2 ). 
     With reference to FIG. 10, in one embodiment of the circuitry for a condensation detection and suppression system of the type shown in FIG. 8, thermal sensor  79 , illustrated as a negative temperature coefficient (NTC) thermistor, but which may be any other temperature-sensing device that performs a similar function, is positioned within ambient space  81 . Thin-film relative humidity sensor  80  is also positioned within the ambient space  81 , in close proximity to thermal sensor  79 . A second thermal sensor  82  is embedded within or affixed to surface  83 . The first thermal sensor  79  is part of a voltage divider circuit, formed by a DC voltage source, resistor  86 , conductors  84  and  85 , and ground  87 . Similarly, the second thermal sensor  82  is part of a second voltage divider circuit, formed by a DC voltage source of the same potential, resistor  90 , conductors  88  and  89 , and ground  91 . As is illustrated in this embodiment, the resistance of each thermal sensor is proportional to the temperature of the material surrounding it. Thus, in the ambient space, the resistance of thermal sensor  79 , and hence the voltage across thermal sensor  79 , is proportional to the temperature of the air in the ambient space, resulting in a finite voltage input through conductor  84  to the analog-to-digital converter (ADC)  92  relative to ground  93 . ADC  92  is supplied power through conductor  104  by voltage regulator circuit  103  that is connected to a DC power source. 
     Similarly, the resistance of thermal sensor  82 , and hence the voltage across thermal sensor  82 , is proportional to the temperature of surface  83 , resulting in a finite voltage input to ADC  96  through conductor  94  relative to ground  95 . ADC  96  is supplied power through conductor  106  by a voltage regulator circuit  105  that is connected to a DC power source. 
     Ambient air or outside air flows over thin-film capacitive sensor  80  in the ambient space  81 . The capacitance of capacitive sensor  80  is proportional to the relative humidity of the surrounding air. Thin film capacitive sensor  80  is connected by conductors  97  and  98  to the capacitance-to-voltage circuit  99 , the relative humidity level thus resulting in a finite voltage input to ADC  101  through conductor  100  relative to ground  102 . The capacitance-to-voltage circuit  99  is supplied power through conductor  108  by a voltage regulator circuit  107  that is connected to a DC power source. ADC  101  is supplied power through conductor  110  by a voltage regulator circuit  109  that is connected to a DC power source. 
     Alternatively, a single voltage regulator connected to conductors  104 ,  106 , and  110  and a single DC power source be may used instead of individual voltage regulators  103 ,  105  and  109 . 
     The voltage level across ambient space thermal sensor  79  is converted in ADC  92  to a digital signal, thereafter being appropriately modified to account for any sensor error or non-linearity, as necessary, by calibration data  111 . Similarly, the voltage level across surface thermal sensor  82  is converted in ADC  96  to a digital signal, thereafter being appropriately modified to account for any sensor error or non-linearity, as necessary, by calibration data  112 . The voltage level across the output conductor  100  relative to ground  102  of the ambient space relative humidity sensor circuit  99  is converted in ADC  101  to a digital signal, thereafter being appropriately modified to account for any sensor error or nonlinearity, as necessary, by calibration data  113 . 
     Internal timer  114  sets the period of data sampling (or data polling) for sample-and-hold buffers  115 ,  116 , and  117 , such that the acquisition of temperature and relative humidity data occurs concurrently. Each buffer may be configured to retain such data in flash memory or in a stack arrangement, such that the newest data replaces the data previously recorded. Subsequently, digital measurement data of ambient space temperature, surface temperature, and ambient space relative humidity are input to central processing unit (CPU)  118  for analysis. CPU  118 , which retains a pre-programmed digital instruction set, accesses a set-point database  119  during computation to establish whether condensation preclusion or removal action is indicated. In such an event, CPU  118  initiates a signal-to-switching circuit  120 , thereby causing internal electronic or mechanical contactors to close. Thereafter, DC electrical power relative to ground  122  is directed from switching circuit  120  through conductor  121  thus energizing components downstream. 
     With reference to FIG. 11, conductor  121  at the output of switching circuit  120  branches into two conductors  123  and  124 . Conductor  123  is connected to a single-speed or multi-speed fan  125  located within duct  129 . When fan  125  is energized, it rotates or increases its speed in order to generate or increase the volume of airflow directed toward the surface, thereby raising the temperature of the surface and the ambient space surrounding it so as to preclude condensation, or alternately if condensation is present, vaporizing water droplets deposited thereon. 
     FIG. 11 illustrates a further option (Option  3 ), according to which electrical power is applied by conductor  124  to electric heating coil  127 . Both the fan and the heating coil are electrically grounded by grounds  126  and  128  respectively. Energization of heating coil  127  raises the temperature of the air flowing over the heating coil element and thereafter flowing to and onto the face of the surface, thereby raising its temperature and the ambient space surrounding it and precluding condensation, or alternatively if condensation is present, vaporizing water droplets deposited thereon. 
     According to a further option (Option  4 ), electrical power is supplied by conductor  124  to an electric motor or solenoid actuator  130 , which is electrically grounded by ground  131 . Electric motor or solenoid actuator  130  is connected by linkage arm  133  to damper  132 , which moves as indicated in FIG. 11 so as to divert the airstream to an adjacent but interconnecting and parallel duct  135  within which a heater core  134  is mounted. Heater core  134  raises the temperature of the airstream passing through parallel duct  135 . Thereafter, heated air is directed toward and onto the face of the surface, thereby raising the temperature of the surface and the ambient space surrounding it so as to preclude condensation, or alternately if condensation is present, vaporizing water droplets deposited thereon. 
     According to a further option (Option  5 ), electrical power is supplied by conductor  124  to TEC controller circuit  136 , which is electrically grounded by ground  128 . TEC controller circuit  136  subsequently energizes TEC  138 , through electrical conductors  139  and  140 . TEC  138  is positioned relative to duct  129  such that its cold side face directly contacts the exterior surface of, and is mechanically attached, bonded, or otherwise affixed to duct  129 . In the same location, heat sink  141  is mechanically attached, bonded or otherwise affixed to the inside surface of duct  129 . Heat sink  141  is comprised of a thermally conductive material, which may be constructed with fins, protrusions, or similar extensions, as illustrated. Duct  129  extends past TEC  138  and heat sink  141 , thereafter attaching to a 180-degree elbow  144  of the same cross-sectional area and dimensions as duct  129 , and positioned within the same plane. Thereafter, elbow  144  attaches to a further duct  143 , of the same cross-sectional area and dimensions as duct  129 , and is positioned within the same plane as the distal end of elbow  144 . Duct  143  extends parallel to duct  129  such that it extends past TEC  138  as illustrated. The hot side of TEC  138  directly contacts the exterior surface of, and is mechanically attached to, bonded to, or otherwise affixed to duct  143 . In the same location, heat sink  142  is mechanically attached to, bonded to, or otherwise affixed to the inside surface of duct  143 . Heat sink  142  is comprised of a thermally conductive material, which may be constructed with fins, protrusions, or similar extensions, as is illustrated. 
     In addition to energizing TEC controller  136 , switching circuit  120  also concurrently energizes a single-speed or multi-speed fan  125  through conductor  123 . Fan  125  is located within duct  129  and is electrically grounded by ground  126 . When fan  125  is energized, it rotates or increases its speed in order to generate or increase the volume of airflow directed through duct  129 , the airstream flowing past and through TEC cold side heat sink  141 , causing moisture in the airstream to be condensed into droplets  145  and to be removed and thereafter past and through TEC hot side heat sink  142 , so as to be re-heated and directed toward the surface, thus directing warmed and dehumidified air toward the surface so as to provide condensation suppression action. Water droplets  145  pass to the lower interior surface of elbow  144  in which an opening and drain trap  146  are affixed. Drain trap  146  is constructed with a loop seal so that air passing through duct  129  and elbow  144  are precluded from escaping through trap  146  by the coalesced condensate  147  collected therein. As further moisture droplets  145  are created that then pass to elbow  144  and into trap  146 , the increased volume of condensate  147  within trap  146  causes a hydraulic pressure imbalance, resulting in the ejection of condensate, as is illustrated. 
     A further illustrative embodiment of a condensation detection and suppression system is shown in FIG.  12 . Goggles  148  may be intended for underwater use such as by swimmers, but may also be of the type used by construction workers, carpenters, skiers, hazardous materials workers, the military, pilots, etc. Goggles  148  have a transparent faceplate  149 , whose inner surface is to be monitored for defogging purposes, and have a circular hole  150  cut out of upper horizontal seal  151 . A sensor circuit board  152 , positioned in an inverted fashion and containing a humidity sensor and a temperature sensor, is mounted to the underside of a main circuit board  154 . The humidity sensor and temperature sensor reside within a protective enclosure  153 , which may be fabricated in part out of a hydrophobic material, so as to permit the transference of gases across its boundary but be impermeable to liquid water. Sensor circuit board  152  and protective shroud  153  extend beneath and protrude below the bottom plane of hermetically sealed enclosure  155  such that, when enclosure  155  is affixed to goggles  148  thus mating with upper horizontal seal  151 , circuit board  152  and protective shroud  153  insert within hole  150 . In such a position, the humidity and temperature sensors (and protective shroud) are placed within the enclosed ambient space formed by the goggles&#39; inner surfaces and the wearer&#39;s face. 
     Main circuit board  154  also contains CPU  156 , voltage regulators  157 , ADC&#39;s  158 , and integrated switching mechanism  159 . Batteries  160  and  161 , positioned within cylindrical recesses  162  and  163 , supply direct-current electrical power to main circuit board  154  and sensor circuit board  152 . Gasketed threaded end caps  164  and  165  provide hermetic sealing of battery enclosures  162  and  163  respectively. 
     FIG. 13 illustrates the juxtaposition of the device&#39;s ambient-space humidity and thermal sensor with respect to the hydrophobic protective enclosure. Shown rotated along a horizontal axis 180-degrees from that depicted in FIG. 12, humidity sensor  166  and thermal sensor  167  are mounted on common sensor circuit board  168  (corresponding to circuit board  152  of FIG.  12 ). Protective enclosure  169  (corresponding to protective enclosure  153  of FIG.  12 ), also shown rotated from its position as depicted in FIG. 12, is of a size and volume sufficient to completely envelop the circuit board  168  and its components. Hydrophobic cover  169  ensures that, should liquid water flood the ambient space (in this case, the space between the inner surface of the goggles and the wearer&#39;s face), the device will still work once the water is cleared off of the inner surface of the goggles. Liquid water can still remain in the bottom of the ambient space, but any that splashes or floods the top of the ambient space (where the sensors reside) is prevented by the protective hydrophobic cover from fouling the sensors. 
     With reference to FIG. 14, the ambient space temperature, ambient space relative humidity, and surface temperature levels held in the sample-and-hold buffers are supplied to the central processing unit for analysis according to either of two alternatives as shown. In the first alternative, the CPU computes or determines, through direct calculation (using the Clausius-Clapeyron Equation or any of its derivatives), by accessing an internal look-up table, or by sequentially accessing a look-up table and interpolating or extrapolating and calculation, the theoretical saturated steam pressure in the ambient space at the ambient space temperature. Thereafter, the CPU multiplies this ambient space saturated steam pressure value by the ambient space relative humidity level supplied to it, so as to determine the actual partial pressure of steam in the ambient space. Thereafter, the CPU computes or determines, through direct calculation (using the Clausius-Clapeyron Equation or any of its derivatives), by accessing an internal look-up table, or by sequentially accessing a look-up table and interpolating or extrapolating and calculation, the theoretical saturated steam pressure at the surface temperature previously provided to the CPU. Finally, the CPU compares, by division, the ambient space steam partial pressure to the saturated steam pressure at the surface temperature, to obtain a “pseudo RH” value. This computed value is then compared to the value limit or limits stored in a set-point database. For example, if the value is 1.0 or greater, then condensation either exists on the surface being monitored or is imminent, and defogging action is initiated. If the value is about 0.93 to 1.0, condensation is likely, and preclusive defogging action is initiated. If the value is less than about 0.93, condensation is not likely, and no action is required. Thus, in the event that the computed value is within the bounds or constraints of the database, no action is taken to preclude condensation conditions or remove condensation on the surface. The device then nulls input data values, returns and re-polls the sample and hold buffers and performs a further computational analysis as previously described. In the event that the computed value is outside the bounds or constraints of the database, action is taken to preclude condensation conditions and/or remove condensation on the surface. While this action continues, the device nulls input data values, returns and re-polls the sample and hold buffers, and performs a further computational analysis as described. Condensation preclusion and/or removal action continues until such time that the ratio of the computed ambient space steam partial pressure to the saturated steam at the surface temperature is within the bounds or constraints of the set-point data base. 
     In a second alternative, the CPU computes or determines, through direct calculation (using the Clausius-Clapeyron Equation or any of its derivatives), by accessing an internal look-up table or by sequentially accessing a look-up table and interpolating or extrapolating and calculation, the theoretical saturated steam pressure in the ambient space at the ambient space temperature provided to the CPU. Thereafter, the CPU multiplies this ambient space saturated steam pressure value by the ambient space relative humidity level supplied to it, so as to determine the actual partial pressure of steam in the ambient space. Thereafter, the CPU computes or determines, through direct calculation (using the Clausius-Clapeyron Equation or any of its derivatives), by accessing an internal look-up table or by sequentially accessing a look-up table and interpolating or extrapolating and calculation, the dew-point temperature of the ambient space steam partial pressure. This value is subtracted from the temperature of the surface, to result in a “pseudo dew point difference” value. Finally, if the CPU-computed value is within the bounds or constraints of the database, no action is taken to preclude condensation conditions or remove condensation on the surface. The device then nulls input data values, returns and re-polls the sample and hold buffers, and performs a further computational analysis as previously described. In the event that the value is outside the bounds or constraints of the database, action is taken to preclude condensation conditions and/or remove condensation on the surface. For example, if the value is greater than about seven, condensation is not likely, and no action is required. If the value is zero or less, then condensation either exists on the surface being monitored or is imminent, and defogging action is initiated. If the value is between zero and about seven, condensation is likely, and preclusive defogging action is initiated. While this action continues, the device nulls input data values, returns and re-polls the sample-and-hold buffers, and performs a further computational analysis as described. Condensation preclusion and/or removal action continues until such time that the difference between the ambient space dew-point temperature and surface temperature is within the bounds or constraints of the set-point database. 
     There have been described devices and methods for sensing condensation conditions, and for preventing and removing such condensation from surfaces. It will be apparent to those skilled in the art that numerous additions, subtractions, and modifications of the described devices and methods are possible without departing from the spirit and scope of the appended claims. For example, instead of the condensation preclusion and/or removal mechanisms being activated directly by the circuitry disclosed herein, the circuitry could provide a warning to a user of a vehicle that includes the windscreen, the goggles, the helmet that includes the visor, the computer monitor that includes the screen, the room or enclosure that includes the window, the electronic equipment that includes the enclosure, etc., thereby causing the condensation preclusion and/or removal mechanism to be activated by the user.

Technology Classification (CPC): 5