Abstract:
An electronic pressure instrument that is easy to monitor and calibrate, and is relatively small and functional, is disclosed. The electronic pressure instrument includes two pressure inputs for receiving two fluids, which can eventually be provided to a transducer for converting a pressure differential of the two fluids to an electrical signal. Positioned between the two pressure inputs and the transducer is a rotatable valve having a mechanical test port and a plurality of conduits for selectively directing at least one of the fluids to the transducer or the mechanical test port. When the valve is in a first position, the two fluids are directed to the transducer. When the valve is in a second position, the at least one fluid is directed to the mechanical test port.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to measurement instruments and, more particularly, to a flexible, efficient, and easy-to-use mechanical-to-electrical measurement instrument. 
     Measurement instruments are growing in popularity because of their small size and increasing functionality. However, despite the advances of size and functionality, many mechanical-to-electrical measurement instruments still require continual monitoring and calibration to retain measurement accuracy. 
     For example, an electronic device for measuring pressure (an electronic pressure gauge) must often be compared to a known reference, such as a mechanical pressure standard. This is often due to the inability of a pressure to electric transducer or other component(s) to maintain an accurate output. As a result, many such electronic devices include electronic output adjustments. For example, potentiometers or variable resistors are often included to allow a user to monitor and calibrate these electronic devices to a known reference. 
     In typical operation, an electronic pressure gauge goes through a routine monitoring cycle. Periodically, the output of the electronic pressure gauge is recorded. The pressure source is then measured by a reference pressure standard. If the output from the reference pressure standard is equal to the output from the electronic pressure gauge, then the gauge is assumed to be operating properly. 
     The electronic pressure gauge may also (or alternatively) go through a routine calibration cycle. A typical calibration cycle requires that the electronic pressure gauge be removed from the pressure source and connected to a source with a known output. To pass calibration, the electronic pressure gauge must provide an output that is equal (within limits) to the known output. The known output can be adjusted throughout an operating range to calibrate the electronic pressure gauge across that range. 
     What is needed is an electronic pressure gauge that is easy to monitor and/or calibrate, and is relatively small and functional. 
     SUMMARY OF THE INVENTION 
     A technological advance is achieved by an electronic pressure instrument that is easy to monitor and calibrate, and is relatively small and functional. In one embodiment, the electronic pressure instrument includes two pressure inputs for receiving two fluids, which can eventually be provided to a sensor/transducer for converting a pressure differential of the two fluids to an electrical signal. Positioned between the two pressure inputs and the transducer is a rotatable valve having a mechanical test port and a plurality of conduits for selectively directing at least one of the fluids to the transducer or the mechanical test port. When the valve is in a first position, the two fluids are directed to the transducer. When the valve is in a second position, the at least one fluid is directed to the mechanical test port. 
     In some embodiments, when the valve is in the second position, the at least one fluid is also directed to the transducer. 
     In some embodiments, when the valve is being rotated to the second position, at least one fluid is continually directed to the transducer. 
     In some embodiments, when the valve is in a third position, the first and second fluids are diverted from the transducer. In some embodiments, when the valve is in the third position, the conduits are operable to direct two different fluids from the mechanical test port to the transducer. 
     In some embodiments, the conduits are operable only when test lines have been engaged with the mechanical test port. 
     In some embodiments, the mechanical test port is operable to rotate the valve by engaging test lines with the mechanical test port and rotating the test lines. 
     In some embodiments, the valve includes a spring for returning the valve to the first position whenever the test lines are disengaged with the mechanical test port. 
     In some embodiments, the instrument includes an electrical test port for receiving an external electrical test device, thereby allowing the device to monitor an output of the transducer. 
     In some embodiments, a DIN rail clip is included for mounting the instrument onto a pair of DIN rails. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of two electronic pressure instruments according to different embodiments of the present invention. 
     FIG. 2 is an isometric cut-away view of one of the electronic pressure instruments of FIG.  1 . 
     FIG. 3 is a side cross-sectional view of the electronic pressure instrument of FIG.  2 . 
     FIGS. 4 a  and  4   b  are functional diagrams of a valve cylinder of the electronic pressure instrument of FIG. 2 being in an operating mode position. 
     FIGS. 5 a  and  5   b  are functional diagrams of a valve cylinder of the electronic pressure instrument of FIG. 2 being in a monitoring mode position. 
     FIGS. 6 a  and  6   b  are functional diagrams of a valve cylinder of the electronic pressure instrument of FIG. 2 being in a calibrating mode position. 
     FIG. 7 is an isometric view of another embodiment of a valve cylinder. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1, the reference numeral  10  refers to a measurement system embodying features of the present invention. In one embodiment, the measurement instrument  10  includes two electronic pressure instruments  12  and  14 . Each instrument  12 ,  14  includes a plurality of faces, including a front face  12   f,    14   f,  a back face  12   b,    14   b,  and a top face  12   t,    14   t,  respectively. The two electronic pressure instruments  12 ,  14  are similarly configured, except where explicitly describe below. Therefore, to describe the similar configuration, only the electronic pressure instrument  14  will be discussed. 
     The back face  14   b  of the electronic pressure instrument includes a mounting system. In one embodiment, a DIN rail clip  16  is used to selectively mount the instrument  14  to a mounting rail  18 . The mounting rail  18  includes a rail channel  20  in a conventional DIN rail geometry that allows standard components to be mounted to the rails. Conventionally, DIN rails are used for items such as junction boxes and circuit breakers, but are used in the present embodiment to attach the two electronic pressure instruments  12  and  14 . 
     The integration of the DIN rail clip  16  for the mounting rail  18  directly addresses the cost of installation by reducing labor and the potential size of the electronic pressure instruments  12  and  14 . Conventionally, a system includes some type of programmable controller along with other associated test devices, such as low pressure differential sensors. Even the smallest sensor available uses a two hole mounting scheme to affix the sensor to the cabinet. Several actions result from this conventional mounting scheme. The installer must drill and tap two holes, by hand, for each transducer to be mounted on a panel. The panel is quite large because of the amount of equipment that is assembled thereon. The fact that several transducers are used often makes the panel even larger because the end to end mounting technique used (a result of the transducer package) forces the width of the panel to grow. These all add to the cost of installation. 
     The top face  14   t  of the electronic pressure instrument  14  includes two fluid inputs  22 ,  24 . The inputs  22 ,  24  are for connecting with two fluid sources (not shown) in a leak proof manner and directing the fluid into the pressure instrument  14 . It is understood that discussion of fluid flow and fluid movement are, in the present embodiment, directed towards fluid pressure measurement. 
     The front face  14   f  of the electronic pressure instrument  14  includes a plurality of indicators  30 . In one embodiment, the indicators  30  are light emitting diodes. The front face  14   f  also includes two test ports  32   a,    32   b  (collectively designated with the numeral  32 ). The test ports  32  allow two probes (not shown) to be inserted to measure an electrical output of the pressure instrument  14 . The probes may form a serial or parallel connection with the test ports  32 , as needed. 
     The front face  14   f  also includes a plurality of calibration devices  34   a,    34   b.  In one embodiment, the calibration devices are two potentiometers that can be manually adjusted. The calibration devices can be used for a calibration mode, discussed in greater detail, below. The front face  14   f  also includes a plurality of electrical outputs  36 ,  38 . In one embodiment, the electrical outputs  36 ,  38  produce the electrical voltage differential (or current, as desired) responsive to a pressure differential from the two inputs  22 ,  24 . This operation is also discussed in greater detail, below. 
     The two electronic pressure instruments  12 ,  14  are different in that the front face  14   f  of the instrument  14  includes a valve port  40 . The valve port  40  allows an external probe (not shown) to be selectively connected to the instrument  14  and to perform various monitoring and/or calibration activities. These activities are discussed in greater detail, below. 
     Referring now to FIGS. 2 and 3, another embodiment of an electronic pressure instrument is designated with the reference numeral  50 . Components of the electronic pressure instrument  50  that are identical to those of electronic pressure instruments  12  and  14  (FIG. 1) are similarly numbered. 
     The electronic pressure instrument  50  includes a plastic shell  52  with a plurality of faces, including a front face  52   f.  The front face  52   f  includes a plurality of indicators  54 . In one embodiment, the indicators  54  are light emitting diodes (LED&#39;s) that are activated to indicate the conditions identified in Table  1 , below. 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 LED 
                 Condition 
               
               
                   
               
             
             
               
                 54a 
                 the pressure differential is positive, and exceeds a preset limit 
               
               
                 54b 
                 the pressure differential is within positive operating limits 
               
               
                 54c 
                 there is no pressure differential 
               
               
                 54d 
                 the pressure differential is within negative operating limits 
               
               
                 54e 
                 the pressure differential is negative, and exceeds a preset limit 
               
               
                   
               
             
          
         
       
     
     The front face  52   f  also includes two test ports  56   a,    56   b.  The test ports  56   a,    56   b  allow two probes  57   a,    57   b,  respectively, to be inserted to measure an electrical output of the pressure instrument  50 . The probes may form a serial or parallel connection with the test ports  56   a,    56   b,  as needed. In the case of a serial connection for measuring electrical current, a silicon diode (not shown) can be placed inside the pressure instrument  50  between the two ports  56   a,    56   b.  The low impedance of an amp meter shunts all the current through the meter. This allows a user to know the current output of the sensor, in case an electrical problem exists elsewhere in the electronic pressure instrument  50 , without disconnecting the instrument. 
     The front face  52   f  also includes a plurality of electrical calibration devices  58   a,    58   b.  In one embodiment, the electrical calibration devices are two potentiometers that can be manually adjusted. The calibration devices  58   a,    58   b  can be used for a calibration mode, discussed in greater detail, below. 
     The front face  52   f  also includes a plurality of electrical outputs. In the present embodiment, three electrical lines  62   a,    62   b,    62   c  are connected to three screw-type terminals  64   a,    64   b,    64 c, respectively. The electrical lines  62   a,    62   b,    62   c  further connect to another electrical device (not shown) to provided an electrical representation of the pressure difference between two fluids flowing through the two fluid inputs  22 ,  24 . The terminals  64   a,    64   b,    64   c  can be used to attach additional electrical lines, test equipment, or facilitate other applications. 
     The electronic pressure instrument  50  includes a pressure transducer  70  that receives fluid from two fluid tubes  72 ,  74 , measures the pressure difference between the fluids in the tubes, and converts the pressure difference to an electrical output. For the sake of example, the pressure transducer  70  may be a sensor device as described in U.S. Pat. No. 4,996,627, which is hereby incorporated by reference. The electrical output is then provided to the two electrical lines  62   a,    62   b  and two screw-type terminals  64   a,    64   b.  The third electrical line  62   c  and third terminal  64   c  provide an electrical common voltage. 
     The valve port  40  includes two apertures  82   a,    82   b  that are adapted to receive a probe  84 . The probe  84  includes two test lines  86   a,    86   b,  for engaging with the apertures  82   a,    82   b,  respectively. In one embodiment, the apertures  82   a,    82   b  remain leak proof unless and until the test lines  86   a,    86   b  are inserted. At that time, fluid may flow through the apertures  82   a,    82   b  and the test lines  86   a,    86   b,  respectively. In one embodiment, the probe  84  includes a hand unit  87  so that a person&#39;s hand can easily insert and remove the test lines  86   a,    86   b  into the valve port  40 . Also, the probe  84  is configured with two depressions  88 ,  90  so that the probe can be easily rotated, thereby rotating the valve port  40  when engaged. 
     The valve port  40  is attached to a rotatable selecting valve cylinder  100 . The valve cylinder  100  includes a plurality of apertures for selectively connecting the valve port  40 , the two fluid tubes  72 ,  74 , and the two fluid inputs  22 ,  24 . By rotating the valve port  40 , and thus the valve cylinder  100 , the electronic pressure instrument  50  can be placed in various modes of operation: a normal mode, a monitor mode, and a calibrate mode. 
     Referring to FIGS. 4 a  and  4   b,  the electronic pressure instrument  50  is in the normal operation mode when the valve port  40 , and hence the valve cylinder  100 , is rotated into a first position, as illustrated. The valve port  40  may be easily rotated by engaging the probe  84  (FIG. 3) with the valve port and manually turning the probe accordingly. In this first position, apertures  102   a,    102   b  align with the two fluid inputs  22 ,  24 , respectively, and apertures  104   a,    104   b  align with the two fluid tubes  72 ,  74 , respectively. Aperture  102   a  is connected to aperture  104   a  by an internal routing mechanism  106   a,  and aperture  102   b  is connected to aperture  104   b  by an internal routing mechanism  106   b.  In the present embodiment, the routing mechanisms are conduits formed in the valve cylinder  100 . Fluid can thereby flow from the pressure source  107 , through the fluid inputs  22 ,  24 , through the conduits  106   a,    106   b,  through the fluid tubes  72 ,  74 , and to the sensor  70 . 
     Referring to FIGS. 5 a  and  5   b,  the electronic pressure instrument  50  is in the monitoring operation mode when the valve port  40 , and hence the valve cylinder  100 , is rotated into a second position, as illustrated. In this second position, apertures  108   a,    108   b  align with the two fluid inputs  22 ,  24 , respectively, and apertures  110   a,   110   b  align with the two fluid tubes  72 ,  74 , respectively. Aperture  108   a  is connected to aperture  110   a  by a conduit  112   a,  and aperture  108   b  is connected to aperture  110   b  by a conduit  112   b.  Conduit  112   a  is also connected to aperture  82   a  and conduit  112   b  is also connected to aperture  82   b,  both on the valve port  40 . Fluid can thereby flow from the pressure source  107 , through the fluid inputs  22 ,  24 , through the conduits  112   a,    112   b,  through the fluid tubes  72 ,  74 , and to the sensor  70 . The fluid can also flow through the conduits  112   a,    112   b,  through the test lines  86   a,    86   b,  and to a monitoring device (FIG.  2 ). 
     Referring to FIGS. 6 a  and  6   b,  the electronic pressure instrument  50  is in the calibrating operation mode when the valve port  40 , and hence the valve cylinder  100 , is rotated into a third position, as illustrated. In this third position, the two fluid inputs  22 ,  24  (and hence the pressure source  107 ) are shut off from the two fluid tubes  72 ,  74 , respectively. Apertures  114   a,    114   b  in the valve cylinder  100  align with the two fluid tubes  72 ,  74 , respectively and connected to apertures  82   a,    82   b  through conduits  116   a,    116   b,  respectively. Fluid can thereby flow to and from a calibration device through the test lines  86   a,    86   b  (FIG.  2 ), through the conduits  116   a,    116   b,  and to the sensor  70 . 
     With the above described monitoring and calibration mode operations, no additional devices are required and no manual disconnections must be performed. Once the test lines  86   a,    86   b  are inserted, monitoring and/or calibration can be readily performed. In some embodiments, a spring  100  returns the valve cylinder  100  to the first position, so that after monitoring mode or calibration mode operation has been completed, the test lines  86   a,    86   b  can be simply removed from the apertures  82   a,    82   b  and the pressure instrument  50  returns to normal operating mode. 
     Referring now to FIG. 7, another embodiment of the valve cylinder is identified with the reference numeral  120 . The valve cylinder  120  has many of similar elements as valve cylinder  100  (FIGS.  4 - 6 ), the similar elements retaining the same reference numeral. However, the valve cylinder  120  allows a fluid to continuously flow from the fluid inputs  22 ,  24  to the sensor  70  when the valve cylinder is being rotated from the operating mode position to the monitor mode position (illustrated). 
     To accomplish the continuous flow, two apertures  122   a,    122   b  connect with the fluid input  22  when the valve cylinder  120  is in the monitor mode position, and only one aperture  122   a  connects with the fluid input  22  when the valve cylinder  120  is in the operating mode position. In addition, the aperture  122   a  is beyond the sealing portion of an o-ring  123 a surrounding the aperture  122   b.  That is, the aperture  122   a  remains connected to the fluid input  22  while the valve cylinder is being rotated from operating mode to monitoring mode position. In this way, a fluid  124  can flow from the fluid source, through the aperture  122   a,  through the aperture  104   a,  and to the sensor  70 . The aperture  122   a  is surrounded by two o-rings  125   a,    125   b  so that the fluid  124  is securely directed to the aperture  104   a.  In contrast, the aperture  122   b  is only connected to the fluid input  22  when the valve cylinder is in monitoring mode. In this way, a fluid  126  can flow from the fluid source, through the aperture slot  122   b  (only when the valve cylinder is in the monitoring mode), through a conduit  128 , and through the aperture  82   a.    
     In a similar manner, a fluid  130  can continuously flow from the fluid input  24 , through an aperture  132   a  and through the aperture  104   b.  The aperture  132   a  is surrounded by two o-rings  125   b,    125   c  so that the fluid  130  is continually directed towards the aperture  104   b  while the valve cylinder  120  is being rotated between the operating and monitoring modes. However, a fluid  134  is directed through an aperture  132   b,  through a conduit  136 , and through the aperture  82   b.  An o-ring  123   b  surrounds the aperture  132   b  so that the fluid  134  flows only when the valve cylinder is in the monitoring mode. 
     Additional modifications, changes, and substitutions are intended in the foregoing disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.