Abstract:
An environmental condition monitor ( 200 ) configured for simple upgrade from analog signal output to any of a plurality of digital communication protocols. A display board ( 202 ) includes the analog signal acquisition and processing elements of the device and also includes a pre-positioned but initially inoperative digital communication output connector ( 214 ). A connector board ( 204 ) associated with the display board includes a connector ( 212 ) to which any one of a plurality of digital communication boards ( 210 ) may be selectively connected, depending upon which of a plurality of digital communication protocols is desired. Selective connection of a digital communication board completes a circuit whereby an analog output signal is converted to the desired digital output format and is then communicated back to the now-activated digital communication output connector ( 214 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of prior U.S. Provisional Application No. 61/165,613 filed 1 Apr. 2009, the content of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to environmental parameter monitoring instruments, and more particularly to a room pressure monitoring device. 
     BACKGROUND OF THE INVENTION 
     Environmental parameter measuring systems are well-known in the art for use with temperature control, security control, room pressure monitoring and a variety of other applications that allow a user to monitor and/or control an environment, either directly or remotely. Such systems may be physically supported in numerous ways on a horizontal surface such as a desk, table, floor or ceiling, or on a vertical surface such as a cubicle, wall, or the like. 
     Room pressure monitors are known instruments used to monitor air pressure in a controllable environment. Applications for room pressure monitors include infectious disease isolation rooms in hospitals, animal resource facilities, clean rooms, pharmaceutical manufacturing, asbestos abatement projects or other hazardous areas. Typically, air pressure in a controllable environment is maintained at a different pressure than an adjacent area in order to direct air flow and to prevent or to reduce the risk of cross-contamination. In the instance where a controllable environment contains toxins, for example, the controllable area should be kept under negative pressure relative to an adjacent clean area so that any air leakage will be in the direction of clean air leaking into the contaminated environment. 
     In order for a pressure monitor to work effectively, it must be properly installed, calibrated, serviced, and maintained. This is important because the differential pressures being monitored may be small but the consequences associated with instrument failure or inaccuracy could be significant. 
     Currently available room pressure monitors attach to a surface, such as a wall panel, and typically are shipped or sold as an assembled device, i.e., with the instrument operating components attached to a special outermost fitting or enclosure customized for the specific instrument. The fitting is mounted to a support beam or stud of the wall where it is then wired and connected to airflow tubing. Paneling, such as gypsum, is then used to finish the wall and conceal exposed wiring and tubing. The fitting is located behind the paneling but is sufficiently exposed to re-install the instrument operating components of the device. If the fitting is not installed precisely, the operating components may be difficult to install and/or the instrument may not fit flush to the wall surface and may not provide an air tight seal there between. It is also possible that the instrument operating components are lost or damaged during the disassembly/reassembly process. When these units require repair or calibration, the work involved typically requires at least partial disassembly and/or complete removal. 
     Current instruments are typically configured for either analog or digital communication. Analog instruments are sometimes discarded prior to the end of their useful life because the user decides to upgrade to a digital communication system. 
     Surface mounting of instruments are desired in many applications because they make use of otherwise unused space within a wall, and because the instrument is largely protected from impact damage by the surrounding wall. Also, the vertical face of a wall-mounted surface instrument tends to collect little dust or debris, and it may be relatively easy to clean and to disinfect compared to a horizontal surface of a free-standing instrument. However, there is an ongoing need for surface mounted instruments that provides simplified installation, servicing and upgrading. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention is explained in the following description and in view of the drawings that show: 
         FIG. 1  is a front view of an embodiment of the housing of a room pressure monitor showing a display module rotated to an uppermost or servicing position. 
         FIG. 2  is an embodiment of the room pressure monitor of  FIG. 1  with display module rotated to a lowermost position, as during operation or shipping. 
         FIG. 3  is a front view of a cover plate installed over the room pressure monitor of  FIGS. 1 and 2  in an operating position as seen by a user. 
         FIG. 4  is a partial perspective view of an embodiment of the room pressure monitor of  FIG. 1  sectioned along a horizontal plane, showing operating components, subsurface channeling, and how the cover plate may engage and disengage with the housing. 
         FIG. 5  is an exploded view of an embodiment of the invention showing an exemplary surface and fitting. 
         FIG. 6  is a block diagram of an embodiment of an environmental condition monitor allowing for interchangeable communication protocols. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the invention is illustrated and described herein.  FIG. 1  is a front view of an embodiment of housing  10  of a room pressure monitor  20  in a servicing position. Housing  10  may be a polycarbonate, plastic, or other known material. Housing  10  has an internal volume  35  shaped and sized to receive components  85  and has a front mounting flange (or collar)  15  used for positioning the housing  10  in a desired plane when mounted. 
     Attached by hinge  40  along a top portion of housing  10  is a display module  45  that supports an active electronic display  50 . The term “display” is used herein to refer to an active electrical component that responds to an electronic signal and provides a visual or other humanly perceptible output, and it may include printed circuit board elements, thin film transistors (TFT), a liquid crystal display (LCD) or other desired type of input/output that may be interactive and communicate with components  85  either wirelessly or by a flex cable (not shown). The term “display module” is used herein to refer to the mechanical support structure to which the “display” is mounted. Display  50  can attach to display module  45  by screws, spring clips or other such fasteners  55  such that display  50  can be replaced in the field by simply removing fasteners  55  and unplugging a flex cable, for example. If the display includes a circuit board separate from an output screen, each of these may be secured to the display module separately or the screen may be secured to the board with the board being secured to the display module, and each may be replaced separately as needed. Because display  50  and display module  45  are independent of housing  10 , an advantage of an embodiment of the present invention is that a display  50  larger than housing  10  may be used. This overcomes a problem of prior art devices where all of the instrument constituents had to fit within the specialized fitting (housing), thus mandating the use of relatively large specialized enclosures and/or undersized displays. 
     It is a further embodiment of the invention that display  50  remains functional while display module  45  is rotated about hinge  40 , in order to permit use while accessing internal housing  35  for field calibration, firmware upgrades, etc. Accordingly, display module  45  can rotate approximately 180° from a lowermost operating position as shown in  FIG. 2  to an uppermost maintenance position as shown in  FIG. 1 . An intermediary of these two positions is shown in  FIG. 5 . A mechanism may be used to selectively restrain movement of display module  45  and/or to hold it in a selected position, for instance when accessing operating components  85 . Such mechanisms may include a detent, ratchet, pin, friction joint, pressure cylinder or any other known mechanism for selectively restraining motion. In other embodiments display module  45  may be hinged on other locations of housing  10  or attached by a slide or swivel in order to provide access. Additionally, hinge  40  can be coupled to a slide, swivel, or combinations thereof. 
     Mounting flange (or collar)  15  can be secured to practically any surface by glue, solder, nails, screws or the like, or it may be secured to a standard electrical rough-in box (as shown in see  FIG. 5 ). Collar  15  may have oversized openings  25  formed there through to accept screws  130  and provide a high degree of adjustment for positioning housing  10  relative to an affixing structure. As shown in  FIG. 1 , depressions  135  may be formed on the backside of module  45  that correspond to locations of the screws  130  so that when module  45  is in a lowermost shipping or operating position, heads of screws  130  do not interfere with module  45 , hinge  40  or cover  60 . Hole  165  corresponds to hole  160  and may be used to fixedly connect module  45  to housing  10  during shipping, handling or installation.  FIG. 2  illustrates an embodiment of the invention when instrument  20  is assembled for shipping (or in optional operating mode). Screw  170  is shown connecting holes  160  and  165  thereby joining module  45  with housing  10  for keeping pressure monitoring instrument  20  safe during packaging, shipping and/or use. 
       FIG. 3  represents the appearance of monitor  20  to an end user when cover plate  60  is attached. As shown, cover plate  60  installs over housing  10  and/or display module  45  and furnishes a clean, flush mounting with no visible fasteners. Further, cover plate  60  protects against ingress/egress of gas, particles, or unwanted debris or other forms of contamination. Attachment of the cover is illustrated in  FIG. 4 , which is a partial perspective view of an embodiment of the invention sectioned along a horizontal plane showing pawl  65  engagement with housing  10 . As shown, a cover plate  60  includes pawl  65  extending rearward from and generally perpendicular to a plane of the cover plate  60 . A receiving opening  70  is formed on housing  10  that is shaped and positioned to receive pawl  65 , such that movement of pawl  65  into opening  70  deflects pawl  65  causing it to snap into a flush or mated position. Prior to engaging with housing  10 , pawl  65  may bypass display module  45  or pass through opening  75  formed in display module  45  in various embodiments. In the embodiment illustrated, two pawls  65  are formed on opposite sides of cover plate  60  and engage with a series of notches  80  formed in corresponding openings of housing  10 . As shown, cover plate  60  may be attached to housing  10  with display module  45  in an operating position by inserting pawl(s)  65  through the corresponding opening(s)  75 ,  70  until pawl  65  engages the plurality of notches  80  in sequential order as the cover  60  is moved toward the housing  10 . As cover plate  60  is further urged toward display module  45 , pawl  65  will engage with the next notch in series  80 . Ideally, the process continues until movement of the pawl  65  toward the housing  10  is restricted at an installed position when the first and second seals are seated and the cover plate  60  is secured against the instrument mounting surface (item  150  of  FIG. 5 ) and cover plate  60  can be urged no closer to display module  45 . There is a spring action from the pawl  65  which secures cover plate  60  in place without need for additional fasteners. Furthermore, the range of engagement of pawl  65  with series of notches  80  allows cover plate  60  to be held flush with a surface even if the installation of housing  10  and/or front mounting flange or collar  15  is not in a perfect plane parallel to mounting surface  150 . In an embodiment illustrated by  FIG. 4 , a seal such as gasket  110  is interposed between cover plate  60  and display  50  (or optionally between the cover  60  and the display module  45 , not shown) and another seal such as gasket  120  is interposed between cover plate  60  and a mounting surface  150  about a perimeter of the cover for protection against contamination ingress into the housing  10 . Interposed gaskets  110 ,  120  ensure protection against dust and water spray ingress to a degree sufficient to achieve an ingress protection rating such as IP  54  even if there is some unevenness in the mounting surface  150 . Acceptable gaskets may include 35 durometer closed cell foam or molded elastomeric materials as are typically used in sealing applications. Gasket  120  may further provide for correction of misalignment between housing collar  15  and mounting surface  150  by filling any space that may exist there between. Since the display  50  may also function as a touch screen input device, the cover plate  60  includes a window aligned with the display  50  when in its installed position to allow for tactile contact with the display. Typically the window is simply an opening, thus requiring gasket  110  to prevent the ingress of contaminants. However, one may appreciate that depending upon the functionality of the display  50 , in certain embodiments the window may be a transparent material that is permanently attached to and sealed against the cover  60 , thereby eliminating the need for gasket  110 . 
     Cover plate  60  may be formed of plastic, sheet metal, or other relatively flexible material. Removal of plate  60  may be facilitated by a slight bending such that the pawl  65  is at least partially disengaged from the series of notches  80  and allows plate  60  to be removed from receiving opening  70  and/or display module opening  75 . As shown in  FIG. 4 , a user could push against the front of plate  60  with a thumb at the location of the arrow in  FIG. 4  to slightly bend cover plate  60  inward at that location, thereby rotating pawl  65  causing it to disengage and lift away from the series of notches  80 . Grasping of cover plate  60  for removal may be facilitated by forming finger indentations  140  on the edge of the cover plate  60  or by slots formed for a tool such as a flat blade screwdriver. Even if pawl  65  is not lifted completely away from series of notches  80 , any degree of disengagement of pawl  65  from the notches  80  would reduce the force necessary to pull cover plate  60  away from the surface  150 . 
     Since calibration of monitor  20  and operating components thereof may involve access to internal volume  35 , the present invention provides access to and optimal use of internal volume  35 . An embodiment of the invention therefore includes using wall(s) of housing  10  to serve as additional or optional paths for communicating with operating components  85  or display  50 .  FIG. 4  illustrates an embodiment where a subsurface channel(s)  90  is formed within a wall of housing  10 . Subsurface channel  90  may be produced when fabricating housing  10  by known processes such as injection molding or by mechanical material removal such as drilling. As shown, subsurface channel  90  may be used as part of a flow path for delivery of measured room pressure to a sensor  85  or for additional wiring or other uses. In one embodiment, an input fluid connection  95  may be provided by forming a threaded hole  100  part-way through housing  10  from the rear portion. Threaded hole  100  could be in fluid communication with subsurface channel  90  and may be supplied with working fluid via input fluid connection  95 . An outlet from subsurface channel  90 , optionally surrounded by a gasketed seal  115 , may further be formed to open into housing  10  and used for delivering working fluid to a pressure sensor  85 . Because there is no flow requirement for such a pressure measuring working fluid, the size of subsurface channel  90  may be small. Working fluid may be delivered to any location about housing  10 . Consequently, the use for internal tubing is greatly reduced if not eliminated within internal volume  35 , thereby saving valuable interior space. 
     In order to eliminate the need of having a custom fitting or losing operating components during installation of the custom fitting, an embodiment of the invention includes housing  10  connected to a universal electrical box, such as typically provided during building construction rough-in. As shown in  FIG. 5 , housing  10  may mount to an opening of a surface  150  and connect to a rough-in box  145 , such as a known double deep triple ganged box, by screws  130  that connect with screw receiving ports  155  on the box flange or by other means such as clips or ties. In this embodiment, the triple ganged box  145  provides anchoring support for instrument  20  as well as industry standard attachment points  147  for access to power, wiring and/or other components as necessary. Unlike prior art devices where a surface mounted instrument is mounted within a specialized fitting, the device of  FIG. 5  can be installed into a readily available “off the shelf” roughed-in triple ganged box  145 . This allows the installer to run all of the wiring and plumbing during the construction rough-in phase without having to purchase and store the room pressure monitor in advance of final installation. This saves the unit from being lost or damaged on site. Housing  10  is able to fit within a typical rough-in box  145  without restricting the size of display  50 . Furthermore, the installation can be made flush to surface  150  with interior  35  sealed from the external environment in spite of some imprecision in the installation of rough-in box  145  due to the degrees of mounting freedom provided via screws  30 ,  130 , oversized slots  25 , and gaskets  110 ,  120 . 
     A basic room pressure monitor may be designed for analog communication with other instruments and systems. In an analog installation, analog control signals are received from and sent to control hardware, and analog signals may operate a local display associated with the monitor. Some time after installation of an analog room pressure monitor, the user or building owner may elect to install a digital communication network within the building to permit monitoring and control of the multiple sensors and equipment such as air flow control valves in the building. Such digital communication networks are inherently more reliable and robust than analog communication systems. This modification necessitates upgrading the analog room pressure monitor to communicate over the digital network. Such an upgrade may require the replacement of the room pressure monitor instrument, or if the instrument is so configured, by field installation of a digital communication board in the analog room pressure monitor and connection of that board to the digital communication network. 
       FIG. 6  illustrates certain elements of a room pressure monitor  200  according to the present invention, including the capability to communicate with other building system components according to a digital communication protocol over a digital communication network. The room pressure monitor  200  includes an electrical component board such as display board  202  and a connector board  204  that are electrically connected by a ribbon conductor  206  comprising a plurality of conductors  208 . The connector board  204  further connects to a digital communication board  210  through a pin/socket connector  212 , comprising pins on the digital communication board  210  received within sockets on the connector board  204 . 
     Although not illustrated in  FIG. 6 , the display board  202  includes analog and digital components for measuring and displaying the sensed room pressure and additional components ancillary thereto. In addition to providing electrical connectivity between the display board  202  and the digital communication board  210 , the connector board  204  includes power supply components for supplying power to the various elements of the room pressure monitor  200 . 
     The connector board  204  further includes a connector  214  for connection to elements of the digital communication network. Typically, the connector  214  comprises a three-pin connector: a first pin for carrying transmitted signals, a second pin for carrying received signals and a third ground pin. One skilled in the art will appreciate that conductors other than metal pins may be used to carry some or all of the signals described herein in certain embodiments, such as optical fiber signal conductors. In operation, pressure readings are supplied to the display board for processing and display. The pressure readings are also provided to the communication board  210  via the connector  212 . On the communication board the pressure values are properly formatted to the operative digital communication protocol or format. The digital communication output signal is then supplied to the connector  214 , via conductors of the connector  212 , the connector board  204 , the ribbon conductor  206  and the display board  202 . 
     Although the digital signal output connector  214  is present in the analog portion of the room pressure monitor, i.e., on the connector board  204 , digital data communication does not begin until a digital communication board is plugged into the connector  212  and the board activated. One such digital protocol is know as BACnet, a data communication protocol developed for building automation and control networks under the auspices of the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE). Another known digital protocol is the LonWorks® networking platform developed by the Echelon Corporation. 
     According to one embodiment of the present invention, the room pressure monitor  200  may be provided with basic analog communication circuitry, i.e., the display board  202  and the connector board  204 . The connector board  204  enables simple field connection of either a BACnet or LonWorks® communication board  210  to the connector  212 , i.e., a communication board operative according to the BACnet protocol or a communication board operative according to the LonWorks® protocol. While the number and function of individual conductors within the connector  212  for proper functioning of BACnet and LonWorks® boards may be different, the present invention allows for a combination of those functionalities into the single connector  212  in order to preserve real estate on the connector board  204 . This may be accomplished in one embodiment by configuring the connector  212  with a sufficient number of pins such that while some pins perform the same function in both protocols, dissimilar functions can be accommodated on different pins so that some pins may remain unused by one protocol. 
     Furthermore, when a digital communication board  210  operative according to any selected protocol (e.g., BACnet and LonWorks®) is plugged into the connector  212 , a processor on the display board  202  may interrogate the digital communication board  210  via the ribbon conductor  206  and the connector board  204 . The processor recognizes that the communication board has been plugged into the connector and further determines the type of communication protocol operative on the communication board  210 . According to one embodiment, this may be accomplished automatically by measuring an electrical parameter value on the digital communication board  210 . The electrical parameter value may be determined from a component value such as a unique resistor value or by sensing a short circuit or a voltage value on the digital communication board  210 . Different resistance values or voltages identify different digital communication protocols. According to another embodiment, this determination is accomplished with a user input that provides a protocol identifier via an I/O device. According to yet another embodiment, the processor determines the digital value (a high or a low voltage) on one or more pins of the connector  212 . These digital values are determined by the protocol operative on the digital communication board  210 . 
     After the processor on the display board determines the operative digital communication protocol, the processor enables certain features of the operative communication protocol. For instance, the processor ensures that a unique identification code is appended to all LonWorks® communication signals and enables functions of the room pressure monitor that the communication protocol can accommodate. Also, the display identifies the operative communication protocol under control of the processor on the display board. 
     This single connector dual protocol functionality can be implemented not only on the connector  212  but also on the connector  214  so that the end user can access any available communication protocol via a single output connector, such as the common RS485 connector, typically provided at the rear of the instrument. Furthermore, some or all input/output connectors may be color coded to facilitate rapid and error free field connection. This allows the user to add or change the protocol without the need to remove and rewire the room pressure monitor  200 . 
     When the communication board is detected, the connector  212  is energized for activating and communicating with the digital communication board  210 . The outputs from the display board  202 , such as the room pressure reading, are supplied to the communication board  210  where the information is properly formatted according to the communication protocol associated with the communication board  210 . The analog outputs from the monitor may remain active after the digital communication board  210  has been plugged into the connector  212 . 
     The external digital communication network will receive the digital data output signal from the instrument  200  and may also communicate to the instrument via the digital communications board  210 . For example, the network may interrogate the instrument  200  to determine the current value of pressure, temperature, relative humidity or other measured environmental parameter. The network may also read the measurement range of the instrument  200 , its serial number, alarm setpoint range, etc. If an alarm occurs, the alarm will be transmitted onto the network. The network supervisor can also write to the instrument  200  to reconfigure the unit remotely or to silence an alarm remotely. 
     Although the invention has been described with reference to the BACnet and LonWorks® digital communication protocols, those skilled in the art recognize that the teachings of the invention can be applied to other digital communication protocols and to other communication formats and hardware, such as optical communication over optical fibers. 
     The features described herein simplify the installation and maintenance of surface mounting systems, such as room pressure monitors as sold by the assignee of the present invention. While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. For example, these features may be embodied in instruments other than room pressure monitors, such as a temperature sensor, a humidity sensor, security systems, or other systems. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.