Abstract:
A Hall effect sensor is transported to and away from a conductor to vary the sensitivity range of the sensor to current flow in the conductor. The device comprises a bracket supported on the conductor which holds a jack screw. At the lower end of the jack screw is a sensor block which holds the Hall effect sensor. The sensor block translates in a slide guide of the bracket, but is prevented from rotating. At the upper end of the jack screw is a knob for rotating the jack screw. Rotating the jack screw causes the sensor block to slide closer or farther from the conductor, which varies its sensitivity in measuring a magnetic field generated by a current in the conductor.

Description:
BACKGROUND OF THE INVENTION 
     Hall effect sensors for detecting motion, direction, position, and measuring/monitoring electric current have become increasingly popular over the last decade as advances in sensor design have been made. Hall effect Sensors develop an output signal proportional to the applied magnetic field, such as one generated by a current through a conductor. However, their operational range is limited. For the current to be effectively monitored, the sensor must be positioned with respect to the power conductor such that the magnetic field generated by current is within the operational range of the sensor. The closer the Hall effect sensor is to the power conductor&#39;s surface, the stronger the flux concentration available for the sensor. 
     Prior to the present invention, sensors have been fixed relative to the conductor to which they are coupled. This permitted accurate positioning of the sensor which is critical for precise measurements, but the fixed position reduces its versatility, since the device can only measure currents within a specified range. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention resolves the disadvantages noted above by providing an accurate positioning mechanism for a Hall effect sensor relative to a conductor. The proposed mechanism to achieve accurate positioning with respect to the power conductor&#39;s magnetic field is designed to allow the manual displacement of the sensor in a graduated manner. The sensor(s) will be transported inside a bracket that prevents the rotational or other unwanted motion of the sensor body while a screw generates the linear motion necessary for linear displacement of the sensor with respect to the conductor. Each turn of the screw allows for a specific distance of travel. In this way, the invention presents a simple mechanism for providing fine-adjustment and accurate positioning of a Hall effect sensor. 
     In addition, the invention presents a method for accurately calibrating the mechanism to provide a high degree of precision in positioning the Hall effect sensor for precise measurement of magnetic flux. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a preferred embodiment according to the invention; 
     FIG. 2 shows the embodiment of FIG. 1 in exploded view; and 
     FIG. 3 shows an exemplary circuit employing the sensor of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein FIGS. 1 and 2 show a preferred embodiment of the adjustment mechanism generally at  10 . Sensor  100  will be transported inside bracket  20  that prevents the rotational or other unwanted motion of the sensor body while jack screw  30  generates the linear motion necessary for linear displacement of sensor  100  with respect to conductor  110 . Each turn of jack screw  30  allows for a specific distance of travel. For example, a screw having 24 threads per inch (cm) will provide 0.0417 inches (cm) of movement in one full turn of the screw. 
     Slide block  50 , formed from a molded high-temperature thermoplastic, transports Hall effect sensor  100  in recess  52  of the sensor block. Hall effect sensor  100  may be attached to the slide block using a high temperature epoxy. The slide block travels up and down in slide guide  22  of bracket  20 , which is also formed from molded thermoplastic. Bracket  20  may contain multiple slide guides for multiple slide blocks (and multiple Hall effect sensors). 
     Slide block  50  is positioned in the bracket by jack screw  30 . Sensor slide block  50  is provided with an inverted T-slot section  53 . T-slot  53  captures tip  32  of the jack screw  30  and allows screw tip  32  to turn against shoulders  54  of T-slot  53  as jack screw  30  is adjusted while slide guides  22  prevent rotation of slide block  50 . The slide block  50  may be turned 90 degrees from the position shown in FIG. 1 during assembly to prevent it from sliding off jack screw  30  or additional surfaces (not shown) may be employed for this task. The slot height in relation to screw tip  32  is critical so no uncontrolled vertical motion is created. To prevent any manufacturing tolerances from creating play resulting in unwanted vertical motion, spring washer  40  is assembled between screw post body and slide block  50 . 
     Jack screw  30  is threaded into mating threaded insert  60  held in place by bracket  20 . At the upper end of jack screw  30  is an internal thread  34  and slot  36 , which extends in a plane passing through the axis of the jack screw  30  from the top end of jack screw  30  to a predetermined depth. The outside diameter of the slotted section of jack screw  30  is very close to the inside diameter of adjustment knob  80 . Adjustment knob  80  is installed over the slotted section of jack screw  30  as shown in FIG.  1  and set screw  90  is screwed into internal threads  32  of jack screw  30 . As set screw  90  is screwed into jack screw  30 , the two sections created by slot  34  will start to spread and press against inner wall  82  adjustment knob  80 . This action will set the assembly together, allowing knob  80  and jack screw  30  to turn as one. 
     Knob  80  includes combination stop pointer  84 . The stop is used to prevent jack screw  30  from rotating more than a predetermined angle, such as 350 degrees. The pointer helps the user find the correct position with respect to indicator label  70 . Indicator label  70  is permanently positioned underneath adjustment knob  80 , and is provided with graduation marks and provided with markings to indicate the appropriate perimeter distance from one graduation mark to another. For example, label  70  may be marked with graduation marks and indicating markings showing a scale from 0.5x to 2.5x. 
     As knob  80  is turned counter-clockwise, sensor  100  is moved farther from conductor  110 , and the milli-volt output of sensor  100  will drop. Label  70  is therefore marked starting with lower levels and moving clockwise to the higher levels. 
     The method of assembling the device will now be explained. First, insert  60  is pressed into receiving hole  24  of frame  20  and spring washer  40  is assembled onto the tip  32  of screw  30 . Tip  32  of screw  30  is then inserted into T-slot  53  of sensor block  50 . Jack screw  30  is then threaded in insert  60 . Bracket  20  is then installed onto conductor  110 . Circuit breaker housing  120  is then installed over bracket  20 . Circular label  70  is then installed onto circuit breaker housing  120 . Then a calibration procedure is performed (described in more detail below). The adjusting knob is then installed with set screw  90  to lock knob  80  to jack screw  30 . Finally the unit is tested at all graduated points to millivolt output. 
     Calibration Procedure 
     Calibration is performed before adjusting knob  80  is installed. Once assembled with the cover on, the output of the Hall sensor is tapped and the jack screw  30  is brought all the way down so the face of sensor  100  is against the face of conductor  110 . At this point sensor  100  must have the desired figure (in millivolts) or higher than the desired figure. If higher, jack screw  30  will be turned away from the conductor slowly until the desired value is reached. Adjusting knob  80  will be inserted and held down and against stop pin  72  so indicator  84  points to the correct high reading on graduated dial  70 . Set screw  90  will then be installed locking knob  80  into position. Once this calibration has been performed, a check of all values in the range must be performed. This check must yield the appropriate readings for each value. 
     Circuit 
     FIG. 3 shows an exemplary application of the Hall effect sensor and adjustment mechanism  10  of the preferred embodiment. This circuit includes printed circuit board  221  upon which trip unit  232  is mounted. The electrical contacts  214 ,  216  are shown connected within a three phase electrical distribution system that includes conductors  233 ,  234 ,  235  and the shaped load lugs  219  depicted in phantom, encompass the corresponding Hall sensor  100  within the shaped radial extension  220  within each separate phase. Hall sensors  100  are positioned relative to radial extensions  220  of conductors  233 ,  234 , and  235  by adjustment mechanisms  10 . Three miniature current transformers  236 - 238  are connected within each phase to provide operating power to input ports I 4  and I 5  of the trip unit circuit  232  by means of three separate bridge rectifiers  239 - 241 , conductors  242 ,  243 , and  244 , diode D 1 , FET Q 1  and capacitor C 1 . 
     The conditioning circuit  245  connects between the Hall sensors  100  and the input ports I 1 -I 3  of trip unit  232  and includes current limiting resistors R 1 -R 6 , feedback resistors R 7 , R 9 , R 11  and ground resistors R 8 , R 10 , R 12  connecting with OP AMPs 246-248 in an amplifying stage of the conditioning circuit. The OP AMPs 246-248 connect with OP AMPs 249-251 through limiting resistors R 13 -R 15  and feed-back resistors R 16 R 18  in a rectification stage. Finally, OP AMPs 252-254 connect the input ports I 1 -I 3  of the trip unit  232  through resistors R 19 -R 24 , rectifying diodes D 2 -D 4  and conductors  255 ,  256 , and  257  to complete the inverter stage of the conditioning circuit  245 . 
     The signals inputted from the Hall sensors  100  through the conditioning circuit  245  are processed within the trip unit circuit  232  to determine instantaneous, short time and long time overcurrent conditions in the manner described in U.S. Pat. No. 5,615,075, incorporated herein by reference and a trip signal is outputted over conductor  260  to the gate of switching transistor Q 2  to energize the trip solenoid  258  via output port O 1 . The cathode of Q 2  connects with ground through conductor  261  and output port O 2  to complete the circuit to trip solenoid  258 . Solenoid  258  operates over mechanical actuator arm  259  to electrically isolate and separate movable electrical contacts  203 ,  204 ,  205  within each of the conductors  233 - 235  to interrupt the circuit within each phase of the electrical distribution circuit. 
     While a preferred embodiment of a trip unit Hall effect sensor adjustment mechanism has been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.