Abstract:
An electrical connector apparatus for use with a field device includes a housing having a first end and a second end, an electrical feedthrough subassembly, and a visual indicator viewable from outside the housing. The first end of the housing is configured to mechanically connect to the field device. The electrical feedthrough subassembly extends through at least a portion of the housing and includes a plurality of electrical conductors configured to provide a removable electrical connection at the second end of the housing and a flameproof barrier disposed between the first and second ends of the housing. The visual indicator has a plurality of illumination modes indicative of a power state of the electrical feedthrough subassembly.

Description:
BACKGROUND 
       [0001]    The present invention relates to electrical connectors for use with field devices used at industrial process facilities. 
         [0002]    Industrial process facilities utilize field devices (i.e., industrial process transmitters) to measure, actuate and otherwise control and monitor industrial processes. Examples of field devices include process sensors (for sensing temperature, pressure, flow, etc.), process actuators, process control modules, process alarm modules, process diagnostic modules, etc. In a typical industrial process facility, there will be a relatively large number of field devices deployed at a variety of locations, as desired for particular applications, and each field device can communicate with a distributed control system (DCS) that controls field device operation. Field devices typically have a housing that is specially designed to protect sensitive internal circuitry from the sometimes harsh environments in the industrial process facility, where risks of fires and explosions must be contemplated and equipment appropriately protected. 
         [0003]    The installation and maintenance of field devices in an industrial process facility can be demanding. Many existing field devices do not include displays (e.g., an LCD) like some newer devices, nor do many existing field devices have integral terminal blocks that provide transient protection. The lack of displays or other visual indicators can make it burdensome for facility maintenance personnel to check to see that each and every field device is installed and functioning properly, such as to make sure each field device is powered. Even where a number of field devices are collected in one area of the industrial process facility, it can still be burdensome to check those devices manually without the aid of visual indicators. For instance, safety regulations can limit the ability for workers to open enclosures that are powered, so an indication regarding the power state of field devices can help workers know when enclosures can be opened. 
       SUMMARY 
       [0004]    An electrical connector apparatus for use with a field device includes a housing having a first end and a second end, an electrical feedthrough subassembly, and a visual indicator viewable from outside the housing. The first end of the housing is configured to mechanically connect to the field device. The electrical feedthrough subassembly extends through at least a portion of the housing and includes a plurality of electrical conductors configured to provide a removable electrical connection at the second end of the housing and a flameproof barrier disposed between the first and second ends of the housing. The visual indicator has a plurality of illumination modes indicative of a power state of the electrical feedthrough subassembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of a universal process transmitter connector according to the present invention. 
           [0006]      FIG. 2  is a side view of the universal process transmitter connector engaged with a field device. 
           [0007]      FIG. 3  is a cross-sectional view of the universal process transmitter connector taken along line  3 - 3  of  FIG. 1 . 
           [0008]      FIG. 4  is a schematic illustration of electrical feedthrough circuitry of the universal process transmitter connector. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    In general, the present invention provides a universal process transmitter (UPT) connector for providing power via an electrical feedthrough to a field device for use in an industrial process facility. The UPT connector simultaneously provides a number of benefits in a single, relatively compact package. The UPT connector includes visual indicators that can indicate whether power is being supplied to the field device. The visual indicators can include light-emitting diodes (LEDs) spaced around about the UPT connector that illuminate when power is provided. The UPT connector also includes transient protection circuitry for protecting sensitive internal circuits of a connected field device from surges and other transient events. Furthermore, the UPT connector provides a flameproof and explosionproof barrier (or seal), to prevent flames and pressurization from exiting the field device through the UPT connector, or vice-versa. The UPT connector can be configured to provide quick-connect capability, such as eurofast® or minifast® connection compatibility, and can be housed in a substantially cylindrical connector housing. 
         [0010]      FIG. 1  is a perspective view of a UPT connector  10  having a housing  12  that defines opposite first and second ends  14  and  16 , respectively. In the illustrated embodiment, the housing  12  is substantially cylindrical in shape and has external threads  18  and  20  at the respective first and second ends  14  and  16 . A plurality of planar surfaces  22  are provided on the housing  12  in between the first and second ends  14  and  16  to enable a tool (e.g., a general-purpose wrench) to grip and torque the UPT connector  10 . In the illustrated embodiment, there are six planar surfaces  22  configured like a hex nut. The housing  12  can be made of a metallic material. 
         [0011]    A central portion  24  of the housing  12  is located between the first and second ends  14  and  16 . More particularly, in the illustrated embodiment, the central portion  24  is located between the plurality of planar faces  22  and the second end  16  of the housing  12 . The central portion  24  can have a slightly larger diameter than the first and second ends  14  and  16 , which can both have approximately the same diameter (e.g., approximately 1.27 cm or 0.5 inch). 
         [0012]    Visual indicators  26  are positioned along the central portion  24  of the housing  12 , and are viewable from outside the housing  12 . In the illustrated embodiment, the visual indicators  26  include three LEDs that can be illuminated to indicate the status of a parameter associated with the UPT connector  10 , for example, to illuminate to indicate that power is currently provided through the UPT connector  10 . The LEDs can be any color, though a green color may be desirable for applications where illumination of the visual indicators  26  designates a desirable, normal, “on” or similar operational condition of the UPT connector  10 . Greater or fewer visual indicators  26  can be provided in alternative embodiments, as desired for particular applications. The visual indicators  26  can be circumferentially spaced around the housing  12 , for instance, the three visual indicators  26  can be circumferentially spaced approximately 120° apart from each other. Operation of the visual indicators  26  is explained further below. 
         [0013]      FIG. 2  is a side view of the UPT connector  10  engaged with an exemplary field device  30 , which can be a process sensor (for sensing temperature, pressure, flow, etc.), process actuator, process control module, process alarm module, process diagnostic module, process signal wireless relay transmitter, etc. The field device  30  includes a housing  32  that defines a connection structure  34 . In the illustrated embodiment, the connection structure is an internally threaded cylindrical portion of the housing  32 . The first end  14  of the housing  12  of the UPT connector  10  is threadably engaged to the connection structure  34  of the field device  30 , through in  FIG. 2  the first end  14  of the housing  12  is not visible. The second end  16  of the housing  12  of the UPT connector  10  can be connected to another structure in a similar manner. 
         [0014]    Circuitry for operation of the field device  30  is located and protected within the housing  32 , which is often made of a metallic material and configured to provide suitable protections against fire, explosion, etc. in a variety of industrial process facility locations. As explained further below, the UPT connector  10  can provide a connection between the field device  30  and a suitable power supply (not shown) in order to power the internal circuitry of the field device  30 . 
         [0015]      FIG. 3  is a cross-sectional view of the UPT connector  10  taken along line  3 - 3  of  FIG. 1 . As shown in embodiment illustrated in  FIG. 3 , three wires  36 ,  38  and  40  extend through the housing  12  between its first and second ends  14  and  16 . In a conventional configuration, two wires  36  and  38  provide power and the third wire  40  provides a connection to ground. The UPT connector  10  can be configured to be compatible with commercially available quick-connect structures for ease of connection and disconnection. For instance, the UPT connector  10  can be configured to provide compatibility with Turck Interlink BT eurofast® or minifast® connections or Rosemount ½ inch NPT or M20 connections. The use of quick-connect structures is desirable for speedy installation and disassembly, as well as for reducing the need for tools. 
         [0016]    A barrier  42  is provided within the UPT connector  10  located between the opposite first and second ends  14  and  16  of the housing  12 . The barrier  42  provides a flameproof and explosionproof seal within the UPT connector  10 , thereby preventing flames, pressurized gas, etc. from passing out of the field device  30  through the UPT connector  10 , or vice-versa. Commercial techniques such a brazing or glass-to-metal sealing can be used to form the barrier  42  to meet suitable flameproof and explosionproof rating requirements. 
         [0017]    The three wires  36 ,  38  and  40  are electrically connected to a circuit board  48  potted within the housing  12 . The circuit board  48  is electrically wired to the visual indicators  26  (only one is visible in  FIG. 3 ). 
         [0018]      FIG. 4  is a schematic illustration of electrical feedthrough circuitry of the UPT connector  10 . The circuitry of the UPT connector  10  includes the circuit board  48  having a transient protection circuit  50  for providing protection against line surges and other transient events, a visual indicator circuit  52  for providing a visual indication that the UPT connector  10  is powered, positive and negative terminals  54  and  56 , respectively, for electrical connection to a DC power source, and positive and negative terminals  58  and  60 , respectively, for electrical connection to a field device. 
         [0019]    The transient protection circuit  50  functions in a conventional manner and includes a lightning tube connected to ground, a pair of resistors  64  for limiting charge to diodes in the circuit, low-capacitance diodes  66  to rectify a charge, a first transient absorber  68  (e.g., a Transorb® assembly of mutually opposed Zener diodes, available from Vishay Americas, Shelton, Conn.), and a second transient absorber  70  connected to ground. The configuration and operation of the transient protection circuit  50  is similar to known transient protection circuits. By providing the transient protection circuit  50  within the UPT connector  10 , the need for a separate, external transient protector is eliminated, which can save space and installation time. 
         [0020]    The visual indicator circuit  52  includes redundant diodes  72  connected in parallel, a DC-DC converter  74 , a pulse circuit  76 , and a plurality of LEDs  78 . The diodes  72  drop voltage across a loop of the visual indicator circuit  52  for powering the LEDs  78 . The diodes  72  are provided redundantly to enable the LEDs  78  to remain illuminated even if there is a failure of one diode  72 . The DC-DC converter  74  can have a known configuration, and in one embodiment can have a 0.7 VDC input and a 1.8 VDC output. The pulse circuit  76  provides a duty cycle for supplying current to the LEDs  78  intermittently, which can allow power savings while still giving the appearance that the LEDs  78  are continuously illuminated to the naked eye. The pulse circuit  76  can have a well-known configuration. In the illustrated embodiment, three LEDs  78  are provided in parallel, such that all three LEDs  78  are illuminated together whenever power is provided through the UPT connector circuit. Because the LEDs  78  draw power from the supply that also is delivered to power the field device, the LEDs  78  cease to be illuminated when there is a lack of power through the UPT connector  10  to the field device. This provides “on” and “off” visual indications of the power state of the electrical feedthrough circuitry. 
         [0021]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the particular size of the UPT connector can vary for compatibility with nearly any type component, cable, etc.