Patent Document

FIELD OF THE INVENTION 
     The present invention relates generally to calibration equipment. More specifically, the present invention relates to portable calibration equipment for calibrating electrofusion controllers. 
     BACKGROUND OF THE INVENTION 
     It is known in the welding industry to use electric heat-weldable fittings (also known as electrofusion fittings) formed of thermoplastic materials to fuse two pipe segments together. Such fittings generally include an electrically resistive heating coil or element positioned adjacent to the inside surfaces of the fitting which are to be welded to one or more other thermoplastic members, such as plastic pipe sections. The electrically resistive heating element typically comprises a coil of wire positioned in the thermoplastic material of the fitting, which is connected to electric contacts attached to an outside surface of the fitting. Electrofusion is an effective method for installing branch connections in pipelines, as well as for tapping into a main gas pipeline. Many vendors supply electrofusion fittings, wherein each of the fittings has a particular fusion voltage and fusion time. Such vendors often have a proprietary method for identifying the fitting to be fused or for controlling various fusion process parameters, such as time and voltage applied to the fitting. 
     An electrofusion controller is a known piece of equipment that is connected to an electrofusion fitting and is used to weld many types of fittings to a variety of types of plastic pipe. The electrofusion controller provides the required energy (in the form of electrical current) to properly heat the resistive element embedded in the fitting. If the amount of energy provided is too small, the fitting will not be properly bonded to the pipe. If the amount of energy provided is too large, the plastic itself will begin to degrade. If the fusion is not properly controlled, the resulting joint will be faulty and could fail a pressure test before being put into service, or worse, prematurely fail when put into service. It is therefore vital that the controller provide the correct amount of energy. The electrofusion controller provides this energy by applying a regulated voltage or current output to the resistive element in the fitting for a predetermined amount of time, or until a pre-determined amount of energy has been applied. 
     Since it is the job of the controller to provide a regulated voltage or current for a pre-determined amount of time, it is important that the controller is capable of accurately measuring these parameters. Important parameters include, but are not limited to: output voltage, output current, time, ambient temperature and fitting resistance. Proper calibration of the controller is therefore essential for its proper operation. 
     Traditionally, calibration of electrofusion controllers is carried out by a trained technician in a laboratory environment. As a result, electrofusion controllers must be shipped to a qualified facility so that calibration can be performed (typically once per year). The resultant “down time” usually lasts one or more weeks (including time in transit), which is undesirable and can cost customers shipping fees and lost productivity. As such, there is a need to reduce the down time associated with calibration and to obviate the need to ship electrofusion controllers to remote locations to perform calibration. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an apparatus and method for portable calibration of electrofusion controllers. A portable self-contained calibration device is provided, which presents an electrofusion controller with dummy loads to simulate real fittings to be fused. The calibration device instructs the electrofusion controller to apply electricity to the dummy load. Then, the calibration device measures parameters outputted by the electrofusion controller (such as voltage, current, and time) with predefined parameters. If there is a difference between the expected value and the measured values, the calibration device adjusts the electrofusion controller&#39;s memory. The measurement is repeated with a second independent measurement device to provide accuracy. The calibration device of the present invention therefore allows for field calibration of electrofusion controllers, thereby obviating the need to ship such controllers to remote locations. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the invention will be apparent from the following Detailed Description of the Invention, taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a bock diagram showing a typical electrofusion control system; 
         FIG. 2  is a block diagram showing the portable calibration system of the present invention; 
         FIG. 3  is a block diagram showing the power supply sub-system of  FIG. 2  in greater detail; 
         FIG. 4  is a block diagram showing the microcontroller sub-system of  FIG. 2  in greater detail; 
         FIG. 5  is a block diagram showing the measurement sub-system of  FIG. 2  in greater detail; 
         FIG. 6  is a perspective view showing the portable calibration system of the present invention; 
         FIG. 7  is an interior view of the portable calibration system of the present invention; 
         FIG. 8  is another perspective view of the portable calibration system of the present invention; 
         FIG. 9  is a flowchart showing processing steps implemented by the portable calibration system of the present invention for calibrating an electrofusion controller; 
         FIG. 10  is a block diagram showing the wire resistance device of  FIG. 5  in greater detail; and 
         FIG. 11  is a block diagram showing the 1-wire resistance device of  FIG. 5  in greater detail. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to an apparatus and method for remote calibration of electrofusion controllers, as described in detail below with reference to  FIGS. 1-11 . As used herein, the term “control box” is also used to refer to an electrofusion controller. Furthermore, the terms “remote” and “portable” are used interchangeably throughout the application. 
       FIG. 1  is a block diagram showing a typical electrofusion control system implemented in a typical installation, indicated generally at  10 . The installation  10  includes an input power source  12  connected via a input cable  14  to a electrofusion controller  16 , which is connected via an output cable  18  to fitting adaptors  20   a - 20   b  placed on a fitting  22 . Of course, the arrangement and number of components shown in  FIG. 1  could be varied as desired without departing from the spirit or scope of the present invention. The electrofusion controller  16  provides the required energy to properly heat the element embedded in the fitting  22 . As described below, the electrofusion controller  16  could be programmed to output a certain voltage and current, or it could select the appropriate outputted voltage and current based on programmed instructions. The appropriate outputted parameter could be a function of, among other variables, ambient temperature. 
       FIG. 2  is a block diagram showing the portable calibration system of the present invention, indicated generally at  30 . The calibration device  30  includes an enclosure  32  (which could be in the form of a plastic, durable, suitcase-style enclosure, a metal enclosure, etc.), an aluminum enclosure  34  positioned within the enclosure  32 , a power supply sub-system  36 , a power receptacle and/or battery connector  38 , a cooling fan  40 , a data port  42 , an Ethernet connection  44 , a microcontroller sub-system  46 , a measurement sub-system  48 , and a high-power load enclosure  50 . It is noted that the enclosures  34  and  50  need not be manufactured from aluminum, and that other materials could be used, such as materials with high temperature resistances. Aluminum is advantageous because it facilitates cooling the calibration device  30 . The electronics, specifically the measurement sub-system  48  need to be kept cool. The power supply sub-system  36  is connected to a standard wall plug  52  (e.g., 120 or 240 volts AC) via the a power supply input cable  56 , to provide power to the system. The electrofusion controller  16  is connected to the power receptacle  38  through the input cable  14 , and is further in communication with the data port  42 . The electrofusion controller  16  is also connected to a control box adaptor  54  via the output cable  18 . The control box adapter is further connected with the measurement sub-system  48  via input cable  58 . The data port  42  could be an RS232 serial connection, or any other suitable type of data connection (e.g., parallel cable, twisted pair wire, coaxial cable, etc.) which allows for bidirectional communication between the system  30  and the controller  16 . 
       FIG. 3  is a block diagram showing the power supply sub-system  36  of  FIG. 2  in greater detail. The power supply sub-system  36  includes a fuse  72  connected to power supply input cable  56  and further connected to cooling fan  40 , the transformer having a primary winding  62  and power receptacle  38 B. Primary winding  62  is further connected to secondary winding  64  of the transformer which is connected to a full wave bridge rectifier  66  which, in turn, is connected to voltage regulator  68  which is further connected to the measurement sub-system  48  to provide power to the measurement sub-system  48 . Secondary winding  64  is further in communication with the measurement sub-system so that measurement sub-system  48  can measure the input voltage for calibration. Additionally, the full wave bridge rectifier  66  is connected to a voltage regulator  68  for providing DC power (e.g., 3.3 volts DC) to the microcontroller sub-system  46 . Optionally, a battery connector  38 A can be connected to measurement sub-system  48 , so that the voltage of control box battery  74  can be measured if required for calibration. The battery connector  38 A is also used to provide power to a DC control box  70  during the calibration process. 
       FIG. 4  is a block diagram showing the microcontroller sub-system  46  of  FIG. 2  in greater detail. The microcontroller sub-system  46  includes an embedded computer  80  (e.g., a microcontroller, microprocessor, etc.) receiving various supply voltages from the power supply sub-system  36  and connected to a memory  82 , a real-time clock  84 , the Ethernet connection  44 , the data port  42 , and an LCD touchscreen  86 . In one embodiment embedded computer  80  may be Coldfire Derivative MCF52223CAF80 microprocessor manufactured by Freescale Semiconductor, Inc. The memory  82  could be in the form of non-volatile memory, such as EPROM, EEPROM, flash memory, etc., and could be programmed to include the processing logic discussed below in connection with  FIG. 9  as well as the calibration history of calibration device  30 . Alternatively, such logic could be coded directly into the embedded computer  80 . The embedded computer  80  is in communication with the measurement sub-system  48  and executes the processing logic stored in the memory  82 . Data port  42  allows for bidirectional communication between the electrofusion controller  16  and the calibration device  30 . Ethernet connection  44  allows for bidirectional communication with an external computing device such as a PC, PDA, etc. Additionally, Ethernet connection  44  allows the calibration device  30  to be interconnected with a communications network if desired, for downloading or logging of data from the system as well as for allowing remote access to, and control of, the calibration device  30 . LCD touchscreen  86  directs the operator of the calibration device  30  through the calibration process, for example, by directing the operator to connect different components together, turn on the control box, etc. In an alternate embodiment of the present invention, the microcontroller sub-system  46  maybe substituted with an external computer (e.g., a stand alone computer, personal digital assistant, or any other suitable device, etc.). 
       FIG. 5  is a block diagram showing the measurement sub-system  48  of  FIG. 2  in greater detail. The measurement sub-system  48  includes a first independent measurement device  92  and a second independent measurement device  94 , both of which could be in the form of analog-to-digital (ADC) converters. The first independent measurement device  92  includes a voltage and current measurement device  104 , resistance measurement circuit  120 , temperature gage  106 , AC input voltage  112  in communication with secondary transformer connector  64 A, and, battery voltage  114  in communication with battery connector  38 A. The second independent measurement device  94  contains a voltage and current measurement device  102 , wire resistance measurement device  120 , 1-wire resistance  108 , AC input voltage  110  in communication with secondary transformer connector  64 A, and battery voltage  116  in communication with battery connector  38 A. The 1-wire resistance  108  is further in communication with ID resistance standards  100 , which are pre-defined standards stored in memory. The voltage current measurement devices  102  and  104  connected with various resistors, described below, positioned in high power load enclosure  50 , which operate as dummy loads to mimic resistive elements of fitting  22 . 
     Microcontroller sub-system  46  directs the electrofusion controller  16  to fuse an appropriate resistor based on the electrofusion controller&#39;s fusing capacity. Wire resistance measurement device  120  is connected with fitting resistance standards  98 . The high power load  50 , fitting standard  98 , and ID resistance standard  100  are further connected with computer controlled switching relays  96 . The switching relays  96  are controlled by the microcontroller sub-system  46 . The microcontroller sub-system  46  also directly communicates with the first independent measurement device  92  and the second independent measurement device  94 . 
       FIG. 6  is a drawing showing a perspective view of the calibration unit of the present invention. The calibration unit includes an enclosure  32  having an upper housing portion  132 , a touchscreen  86 , a temperature gage  106 , Ethernet connection  44 , data port  42 , power supply input connection  56 A, the power receptacle  38 B (shown with an optional cover plate in position over the receptacle  38 B), the control box adapter connection  54 A, a fuse holder  138 , and an on/off switch  136 . The fuse holder  138  houses a fuse that prevents overloading of the power supply sub-system  36 . A lower housing portion  134  is also provided, which includes the cooling fans  40  used to cool the high power load resistors enclosed in the lower housing portion  134  (not visible in this view). 
       FIG. 7  is a drawing showing the lower housing portion  134 . The lower housing portion  134  includes a plurality of high power load resistors  140 ,  142 ,  144  and  146  within the high power load enclosure  50 . As discussed above, the load resistors  140 ,  142 ,  144  and  146  provide dummy fusion loads for use in calibrating an electrofusion controller. As can be seen in  FIG. 8 , air flow vents  148  are provided in lower housing portion  134  to facilitate cooling of the load resistors  140 ,  142 ,  144  and  146 . 
       FIG. 9  is a flowchart showing processing steps according to the present invention, indicated generally at  150 , for controlling calibration. In step  152 , the calibration system  30  is connected with the electrofusion controller  16 , power is turned “on,” and the calibration system  30  communicates with the electrofusion controller  16  to determine the fusion load that the electrofusion controller  30  requires. In step  154 , the calibration system  30  selects the appropriate high power load resistor  140 ,  142 ,  144  or  146  which matches the fusion load required by the electrofusion controller  16 . In step  156 , the microcontroller sub-system  46  directs the electrofusion controller  16  to fuse the high power load resistor selected in  154 . In step  158 , the first independent measurement device  92  measures a selected output parameter and in step  160 , that measured parameter is stored in flash memory  82 . In step  162 , the embedded computer  80  calculates the difference between the value of the parameter stored in step  160  and the electrofusion controller&#39;s preset parameter value. 
     In step  164 , if the calculated value in step  162  is greater than allowable error, a pre-defined error threshold established by the manufacturer of the control box  16  and programmed into the nonvolatile memory of the calibration device  30 , step  166  is performed, alternately step  168  is performed. In step  166 , the microcontroller sub-system  46  communicates with the electrofusion controller through data port  42  and calibrates the electrofusion controller&#39;s circuitry to match the stored value for the parameter. In step  168 , the microcontroller sub-system  46  directs the electrofusion controller  16  to fuse the high power load resistor of step  154 . In step  170 , the second independent measurement device  94  measures the previously selected output parameter and stores that measured parameter is stored in flash memory  82 . In step  172 , the embedded computer  80  calculates the difference between the value of the parameter stored in step  168  and the electrofusion controller&#39;s preset value. In step  176 , if the calculated value in step  172  is greater than allowable, step  174  is performed and the operator receives an error message on LCD touchscreen  86  informing them that there was an error in the calibration process and suggesting that the device be sent to its manufacturer for calibration. 
       FIG. 10  is a block diagram showing the wire resistance measurement device  120  of  FIG. 5  in greater detail. In this embodiment, the wire resistance measurement device  120  uses a standard 4-wire resistance measurement system to calibrate control box&#39;s  16  resistance measurement device. The wire resistance measurement device  120  attaches to fitting adaptors  20 A and  20 B and includes switches  182 ,  184 ,  186 ,  188  and  190 , standard resistors  192 ,  194 , and  196 ,  198  and  200 , an excitation voltage  68 A, and ground  210 . The values of the standard resistors  192 ,  194  and  196  and resistor  198  are stored in nonvolatile memory. Switches  182 ,  184  and  186  each connect with standard resistors  192 ,  194 , and  196  respectively. Resistors  198  and  200  in combination with the excitation voltage  68 A and ground  210  by the 4 wire resistance measurement system to independently measure the standard resistors  192 ,  194  and  196  and verify the values stored in nonvolatile memory are correct. Initially, switches  182 ,  184  or  186  are then closed to, one at a time, present standard resistors  192 ,  194  or  196 , one at a time, to control box  16  to measure. Control box  16  is calibrated to ensure its measured resistance matches that stored in nonvolatile memory. Switch  190  and  180  are then closed to allow independent measurement device  92  and  94  to measure the standard resistors  192 ,  194  or  196 . When switches  190  and  188  are closed, current flows from the excitation voltage  68 A through resistors  200 ,  198  and one of the standard resistors that is selected in turn  192 ,  194  and  196  to ground  210 . The voltage drop across the resistance standard that is selected  192 ,  194  or  196  (V std ) is measured directly by independent measurement device  94 . The electrical current flowing through the resistance standard that is selected  192 ,  194  or  196  (I std ) is calculated by the embedded computer  80  using the value of resistor  198  and the voltage measurement supplied by independent measurement device  92 . The value of the standard resistor that is selected  192 ,  194  or  196  (R std ) is then calculated by the embedded computer  80  using the formula R std =V std /T std . Each of the standard resistors,  192 ,  194  and  196  are measured by the above process. 
       FIG. 11  shows the 1-wire resistance  108  used to produce ID resistance standard  100  of  FIG. 5  in greater detail. If needed, the 1-wire resistance  108  measures and calibrates the control box&#39;s  16  ability to measure an additional resistor in fitting  22  through fitting adaptor  20 A. 1-wire resistance  108  attaches to fitting adaptor  20 A and includes switches  222 ,  224 ,  226 ,  228  and  230 , standard resistors  232 ,  234 ,  236  and  238 , an excitation voltage  68 B and ground  240 . The values of the standard resistors  232 ,  234 ,  236  and  238  are stored in nonvolatile memory. Switches  222 ,  224 ,  226  and  230  connect to standard resistors  232 ,  234 ,  236  and  238  respectively. Resistor  238  in combination with excitation voltage  68 B and ground  240  are used by the 1-wire resistance measurement system to independently measure the standard resistors  232 ,  234  and  236  and verify the values stored in nonvolatile memory are correct. Initially switches  222 ,  224  or  226  are closed in turn to present one of standard resistors  232 ,  234  or  236  to control box  16  to measure. Control box  16  is then calibrated to ensure its measured resistance matches that stored in nonvolatile memory. Switch  230  and  228  are then closed to allow independent measurement device  94  to measure the standard resistors  232 ,  234  or  236 . When switches  238  and  228  are closed, current flows from the excitation voltage  68 B through resistor  238  and standard resistor  232 ,  234  or  236  to ground  240 . The voltage drop across the resistance standard  232 ,  234  or  236  (V std ) is measured directly by independent measurement device  94 . The electrical current flowing through the resistance standard  232 ,  234  or  236  (I std ) is calculated by the embedded computer  80  using the value of resistor  238  and the voltage measurement supplied by independent measurement device  94 . The value of the standard resistor  232 ,  234  or  236  (R std ) is then calculated by the embedded computer  80  using the formula R std =V std /I std . It should be noted that excitation voltage  68 A and  68 B of  FIGS. 10 and 11  could be supplied from voltage regulator  68 . 
     The controller may be programmed to calibrate different parameters in the following sequence: resistance, AC input voltage and/or battery voltage, output current, output voltage, temperature, and ID resistance. It should be noted that the sequence of calibration could be varied, or other parameters could be included, without departing from the spirit or scope of the present invention. 
     Having thus described the invention in detail, it is to be understood that the foregoing description is not intended to limit the spirit or scope thereof. What is desired to be protected by Letter Patent is set forth in the appended claims.

Technology Category: b