Abstract:
A pressure monitoring apparatus ( 10 ) including features that simplify in-situ calibration procedures. A pressure monitoring module ( 12 ) of the apparatus is coupled to external pressure lines ( 14, 16 ) and an external electrical interface ( 24 ) via an easily removable monitoring module plug ( 32 ). The monitoring module can be disconnected from the pressure lines and external interface and then connected to a portable calibration module ( 42 ) by simply replacing the monitoring module plug with a calibration module plug ( 50 ). The calibration module plug provides an electro-pneumatic interface between the monitoring module and the calibration module. The monitoring module may be electronically interrogated and automatically calibrated via a processor of the calibration module. The monitoring module plug may be inserted onto the calibration module plug to provide actual system pressures to the now-calibrated apparatus for final documentation. Touch-screen ( 28 ) interface with the monitoring module provides an one-touch calibration of Zero and Span.

Description:
[0001]    This application claims benefit of the 30 Sept. 2008 filing date of U.S. provisional application 61/101,481. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to the field of fluid pressure monitors for ambient air conditions for rooms, and to the calibration of such monitors. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fluid pressure monitors are used in a large variety of applications over a wide range of pressures and with varying requirements for accuracy. Very low differential ambient air pressures, on the order of a full scale range of 0.1 inch of water or less, must be measured with a high degree of accuracy in applications such as manufacturing clean rooms, medical isolation wards, and various HVAC systems. Periodic calibration of such devices is required to ensure and to document their proper operation. 
         [0004]    U.S. Pat. No. 5,693,871, incorporated by reference herein, describes a pressure generator that may be used to calibrate differential pressure transducers that operate at very low differential pressures. 
         [0005]    U.S. Pat. No. 6,584,421, also incorporated by reference herein, describes an instrument calibration device that incorporates a portable computer as its user interface in order to simplify the use of the device for calibrating a variety of instruments and for recording the results of such calibrations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The invention is explained in the following description in view of the drawings that show: 
           [0007]      FIG. 1  is a schematic illustration of a room pressure monitoring apparatus in an operational configuration. 
           [0008]      FIG. 2  is a schematic illustration of the room pressure monitoring apparatus of  FIG. 1  in a calibration configuration including a portable calibration module. 
           [0009]      FIG. 3 . is a schematic illustration of the room pressure monitoring apparatus of  FIG. 2  in a further calibration configuration. 
           [0010]      FIG. 4  is a Starting screen display of the monitoring module of the room pressure monitoring apparatus of  FIG. 1 . 
           [0011]      FIG. 5  is a Menu screen display of the monitoring module of the room pressure monitoring apparatus of  FIG. 1 . 
           [0012]      FIG. 6  is a Calibration screen display of the monitoring module of the room pressure monitoring apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    The assignee of the present invention provides calibration equipment for instrument calibration service that satisfies ISO documentation standards requirements, that is performed in compliance with ANSI/NCSL Z540-1-1994, and that is certified per NIST traceable primary standards. For the owners and operators of large numbers of pressure transducers, on-site calibration may be an economically viable alternative to shop-based calibration. Portable calibration devices, such as the Model 869 Micro-Cal™ calibration system sold by the assignee of the present invention, provide the capability to deliver a highly accurate calibration source directly to the location of a pressure monitoring installation. A pressure transducer is removed from its operating position, inserted into the Model 869 Micro-Cal™ calibration system, and then reinstalled immediately following the calibration procedure, thereby avoiding the downtime and expense associated with shipment to a central calibration service location. 
         [0014]      FIGS. 1-3  are schematic illustrations of an improved pressure monitoring apparatus  10  in various configurations, such as may be used for low differential pressure applications for example. A monitoring module  12  of the pressure monitoring apparatus  10  is illustrated in  FIG. 1  in an operational configuration as it functions as an active transducer in an operating system, such as a room pressure monitoring application. A monitored pressure (room pressure) and a reference pressure are provided to the device by respective room and reference pressure lines  14 ,  16 . A differential pressure sensor  18  of any known type, such as capacitive, inductive, strain gauge for example, converts the difference in pressure between the two lines  14 ,  16  into an electrical signal  21 , such as a frequency output proportional to measured pressure. An electrical terminal  22  is provided for removable electrical connection of the appropriate monitoring module electrical connections  20  to various external electrical interfaces  24 , such as a power supply, remote display, remote controller, etc. For simplification of the drawings, electrical connections are illustrated in these figures as single lines that may represent a plurality of power, control and/or signal functions as known in the art. A controller  26 , such as any known microprocessor and memory (EPROM), provides the appropriate control, memory and processing functions and operatively interconnects the various components of the monitoring module  12 . User interface may be provided by an input/output device or devices such as touch screen  28 . All of these components may be supported directly or indirectly by a frame  30  that is mountable to a wall, rack or other desired support structure or surface. 
         [0015]    The apparatus  10  also includes a monitoring module plug  32  that may be selectively attached or removed from the monitoring module  12 . The monitoring module plug  32  provides a plug-in connect/release fluid connection between the room and reference pressure lines  14 ,  16  and respective pressure ports  34 ,  36  of the differential pressure sensor  18 . The pressure lines  14 ,  16  may be installed over barbed tips to provide a tight fluid seal and strong mechanical connection which need not be disturbed during subsequent calibration procedures. The fluid seal between the monitoring module plug  32  and the monitoring module  12  may include a flexible gasket or O-ring (not shown). Additionally, the plug may be held in place once installed on the monitoring module  12  by friction or by any type of known locking device, such as screws or clips for example (not shown). 
         [0016]    The monitoring module plug  32  may also include electrical conductor(s) that provide plug-in connect/release electrical continuity between the electrical terminal  22  and the various other electrical connections  20  of the monitoring module  12  when the plug  32  is installed on the monitoring module  12 . One embodiment of the monitoring module plug  32  was made by modifying a standard D-sub electrical connector to include fluid passages in the location normally occupied by the screw fasteners. Accordingly, when the monitoring module plug  32  is disconnected from the monitoring module  12 /frame  30 , the pressure ports  34 ,  36  and the electrical connections  20  are disconnected from the respective pressure lines  14 ,  16  and external electrical interfaces  24 . 
         [0017]      FIG. 2  illustrates the pressure monitoring apparatus  10  in a calibration configuration where the monitoring module plug  32  has been removed, thereby making the pressure ports  34 ,  36  and the electrical connections  20  available for connection to a portable calibration module  42 . The calibration module  42  includes a calibration pressure source  44  such as the pressure generator described in U.S. Pat. No. 5,693,871 discussed above. The calibration pressure source  44  provides precise, controllable and repeatable fluid pressures to pressure outlets  46 ,  48 . These pressure outlets are selectively fluidly connected to the monitoring module pressure ports  34 ,  36  by an electro-pneumatic interface  49 . The electro-pneumatic interface  49  is connected at its proximate end to the calibration module  42  in any desired manner. At its distal end, the electro-pneumatic interface  49  may include a calibration module plug  50  adapted for selective installation on the monitoring module  12 /frame  30  in place of the monitoring module plug  32  to enable calibration of the pressure sensor  18 . The electro-pneumatic interface  49  includes fluid passages  52 ,  54  for interconnecting the monitoring module pressure ports  34 ,  36  with the calibration module pressure outlets  46 ,  48 , and it also includes electrical conductor(s)  56  for interconnecting calibration module electrical connections  58  with the monitoring module electrical connections  20 . Here again, to simplify the drawings, all power, control and signal conductors are graphically illustrated as a single line. Also, no power supply is illustrated, but one skilled in the art will appreciate that a battery pack or other source of power would be associated with the portable calibration module  42 . The electro-pneumatic interface  49  may be fabricated as a single integrated Electro-pneumatic Interface Cable (EPIC), although one skilled in the art will recognize that multiple cables/plugs may be used in other embodiments to accomplish similar functions. 
         [0018]    As can be seen in  FIG. 2 , the external electrical interfaces  24  are isolated from the monitoring module in the calibration configuration, and the monitoring module electronic components  26 ,  28  are interconnected with the calibration module processor  60 . Interrogation, control and operation of the monitoring module  12  may be accomplished via the calibration module  42  in this configuration. For example, an EPROM of controller  26  may be interrogated by the calibration module  42  to identify the type of monitoring module  12  that is connected to the EPIC, whereupon data related to that identity may be recalled from memory and used by the calibration module  42 , such as for automatically selecting an appropriate full scale pressure for the calibration process, or an accuracy code, or a serial number as examples. The processor  60  may then execute programmed instructions for automatic calibration of the monitoring module  12 , such as: 
         [0019]    apply a zero differential pressure across the pressure outlets  46 ,  48  (thereby across the pressure ports  34 ,  36  via fluid passages  52 ,  54 ); 
         [0020]    setting a resulting output of the pressure transducer  18  to a desired zero value by responsively programming data in EPROM of controller  26 ; 
         [0021]    applying the previously determined full scale pressure across the pressure outlets  46 ,  48 ; and 
         [0022]    setting a resulting output of the pressure transducer  18  to a desired full scale value by responsively programming data in EPROM of controller  26 . 
         [0023]    The zero differential pressure may be accomplished within the calibration module  42  by appropriate control of valves  61  to shunt both sides of the calibration pressure source  44  to atmosphere. 
         [0024]    As can be seen in  FIG. 2 , the calibration module plug  50  includes monitoring module interface connections  62  for selective connection with the monitoring module  12 . In addition, the calibration module plug  50  may have operating system interface connections  64  on an opposed side for selective connection with the operating system fluid connections via the monitoring module plug  32 , as illustrated in  FIG. 3 . In the configuration of  FIG. 2  during the above-described calibration steps, the operating system interface connections  64  are closed with a blank plug  66 . After the calibration steps have been completed, the blank plug  66  may be removed and replaced with the monitoring module plug  32  previously described with reference to  FIG. 1 . This allows the pressure ports  34 ,  36  as well as the calibration module pressure outlets  46 ,  48  to be exposed to pressure generated in the monitored operating system and delivered by the room and reference pressure lines  14 ,  16 . This configuration is useful for comparing and recording data generated by the pressure sensor  18 /monitoring module  12  and data coincidently generated by the calibration module  42  in response to actual system pressures delivered via the room and reference pressure lines  14 ,  16 . In this manner, the monitoring module  12 , the calibration module  42  and the system operator&#39;s supervisory monitoring system may be reconciled. 
         [0025]    The pressure monitoring apparatus  10  enables calibration of the monitoring module  12  without removing the device from its operational location, and without removing any hard wired connection from the electrical terminal  22 , and without removal of tubing for pressure lines  14 ,  16  from the monitoring module  32 . Furthermore, the touch screen user interface device  28  provides further capability for in-situ calibration of the device. Programmed code may be executed by the controller  26  for providing a simplified user interface for calibration via the touch screen  28 .  FIG. 4  illustrates a Starting Screen display  68  as may be provided during normal operation of the pressure monitoring apparatus  10 . The real-time measured pressure may be displayed as a numeric value  70  and/or as a graphical presentation  72  showing the location of the real-time actual value in relation to the alarm setpoint limits. The real time display of the entry door status may also be displayed via the touch screen display  28  by a text message or by using color change indication. In addition, Silence and Reset buttons  74 ,  76  may be provided for the operator to use in response to an alarm. The alarm may be provided by an auxiliary device, such as a sound generating device and/or a light emitting device, and/or the alarm may be displayed on the touch screen  28  via a color indication, flashing display or other manner. A Menu selection  78  may also be provided on the Starting Screen display  68 . 
         [0026]    In response to a touch of the Menu selection  78 , a Menu Screen  80  is displayed as illustrated in  FIG. 5 . The Menu Screen  80  includes Setup selections  82 , a Test selection  84  and a Calibration selection  86 . 
         [0027]    In response to a touch of the Calibration selection  86 , a Calibration Screen  88  is displayed, as illustrated in  FIG. 6 . The Calibration Screen  88  includes a Zero selection  90  and a Span selection  92 . Upon removal of the monitoring module plug  32  from the frame  30  (thereby exposing the pressure ports  34 ,  36  to the same atmospheric pressure and a zero pressure differential) and in response to a touch of the Zero selection  90 , the controller  26  may be programmed to set the output of the pressure sensor  18  to a desired zero value (e.g. 0 volts DC or 4 ma, for example) by appropriate data recordation in the controller EPROM. A known full scale pressure may then be applied to the measured room pressure port  34 , and in response to a touch of the Span selection  92 , the controller  26  may similarly set the output of the pressure sensor  18  to a desired full scale value (e.g. 10 volts DC or 20 ma, for example). Thus, calibration of the unit is accomplished in a rapid and convenient manner without the removal of the monitoring module  12  from its operating location. 
         [0028]    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. 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.