Abstract:
A system for testing the safety of electricity includes steps as following. First step is inserting a testing apparatus into a socket of utility power. Second step is providing a first amplifier and rectifier unit for measuring a first voltage wave as no-loading. Third step is providing a signal capturing unit at driver circuit for capturing an instant load cycle current wave. Fourth step is providing a second amplifier and rectifier unit for simulating a second voltage wave according to the instant cycle current wave. At least, a processing unit provides for comparing the first voltage wave with the second voltage wave. Therefore, the above-mentioned method is provided for determining the quality of household electricity wire and further improving the electricity safety.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a testing method and system for electricity safety and in particular to a testing method and system for actively determining the quality of a household electricity wire. 
     2. Description of Prior Art 
     Electricity is widely used in modern life as much of commonly used equipment is driven by electricity. However, electricity can cause some accidents when not used properly. 
     Electricity accidents are often caused by overcharges or short circuits. The conductive wire has a limitation of the current, for example, the limitation “125V, 15 A” marked on the wire signifies that the highest voltage for this wire is 125V and the total current flowing in the wire must be smaller than 15 A. If a user uses several pieces of equipment at the same time, the total current is higher than 15 A, i.e. overcharge or overload, and an accident will occur. Excessive heat will be induced on the wire during overloading and the insulating layer coated outside the wire will melt or burn so that a fire accident occurs. Short circuits also occur in the household equipment. Many reasons cause the short circuit situation, for example the conductive wire inside the plug is broken, the isolation of the power fails, or the two electrodes contacts to each other. The instant current is very large when a short circuit happens. The household environment can also influence electricity safety. For example, it is important to keep the electric equipment in sufficient distance from flammables, and the wire should not be pressed by furniture. 
     For electricity safety, protecting circuits are disposed on household electricity wires such as over-current protection circuits or over-voltage protection circuits. The over current protection circuit can be a fuse made of alloy of Pd, Sn, and Cd metals. The fuse has low melting point so that the fuse is melt because of the heat of high current. The safety fuse can be broken fast so as to protect the equipment from high current. 
     However, the traditional protection mechanism is a passive protection. In other words, the protection mechanism acts on the critical point of an accident. When accidents occur, users do not have much time to control the situation. Furthermore, the traditional protection mechanism can not determine the danger of the wire in advance. 
     Therefore, in view of this, the inventor proposes the present invention to overcome the above problems based on his expert experience and deliberate research. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is provided for a testing system for electricity safety and a testing method thereof. The present invention is applied for actively determining the quality of the household electricity wire in order to prevent houses or people from the danger. 
     In order to achieve the above object, the present invention provides a testing system for electricity safety comprising: a first amplifier and rectifier unit for measuring a first voltage wave of the household electricity wire when no load is applied, a signal capturing unit, a second amplifier and rectifier unit, and a processing unit. The signal capturing unit has a switching device (for example: an MOSFET device, an IGBT device, a driving switch unit and so on) and a first resistor parallel connected to the switching device. The switching device is used for capturing a current signal of the household electricity wire when loading the first resistor and the current signal of the household electricity wire captured by the signal capturing unit is transformed to a voltage signal by a micro-resistor. The second amplifier and rectifier unit is connected to the capturing unit for transforming the voltage signal to a second voltage wave. The processing unit is connected to the first amplifier and rectifier unit and the second amplifier and rectifier unit for comparing the first voltage wave and the second voltage wave and then outputting a comparison result. 
     The present invention is provided for measuring the impedance of the household electricity wire in order to determine the quality of the wire. Users can clearly understand the total situation of the household electricity wires of the house so as to take some necessary act in order to improve the safety of house. 
     In order to better understand the characteristics and technical contents of the present invention, a detailed, description thereof will be made with reference to the accompanying drawings. However, it should be understood that the drawings and the description are illustrative but not used to limit the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram showing the testing system for electricity safety according to the present invention. 
         FIG. 2  is a function block diagram showing the testing system for electricity safety according to the present invention. 
         FIG. 3  is a flow chart shows the testing method for electricity safety according to the present invention. 
         FIGS. 4 to 4B  show the compared voltage according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIGS. 1 and 2 , the invention discloses a testing system for electricity safety  1  for measuring the impedance of the household electricity wire in order to determine the quality of the wire. The testing system for electricity safety  1  has a plug used for inserting into the socket  100  of the household electricity wire. The testing system for electricity safety  1  comprises a first amplifier and rectifier unit  11  for measuring a first voltage wave “a” of the household electricity wire when no load is applied a signal capturing unit  12 , a second amplifier and rectifier unit  13 , and a processing unit  14 . The signal capturing unit  12  has a switching device U 1  (for example: an MOSFET device, an IGBT device, a driving unit and so on) and a first resistor R 1 . The switching device U 1  is used for capturing a current signal of the household electricity wire when loading the first resistor R 1  and the current signal of the household electricity wire captured by the signal capturing unit  12  is transformed to a voltage signal by a micro-resistor. The second amplifier and rectifier unit  13  is connected to the signal capturing unit  12  for transforming the voltage signal to a second voltage wave “b”. The processing unit  14  is connected to the first amplifier and rectifier unit  11  and the second amplifier and rectifier unit  13  for comparing the first voltage wave “a” and the second voltage wave “b” to output a comparison result. According to the comparison result, a user can determined the quality of the household electricity wire. 
     In the preferred embodiment, the amplifier and rectifier unit  11  is a differential amplifier and full-wave/half wave rectifier circuit, and the second amplifier and rectifier unit  13  is also a differential amplifier and full-wave/half wave rectifier circuit, but the present invention is not restricted to above-mentioned devices. The signal capturing unit  12  is disposed between the amplifier and rectifier unit  11  and the second amplifier and rectifier unit  13 . The amplifier and rectifier unit  11  is used for measuring a first voltage wave “a” of the household electricity wire, and the first voltage wave “a” is an experimental voltage thus the processing unit  14  can calculate the reference impedance in order to judge the quality of conductive wire. 
     The signal capturing unit  12  includes a switching device U 1  and a first resistor R 1 . The switching device U 1 , for example but not restricted, is an MOSFET device, an IGBT device, or a driving unit. The switching device U 1  is used for capturing a current signal in an instant loading cycle when the first resistor R 1  is loaded. In the above circuit, the first resistor R 1  is employed for a reference impedance with a good quality of the wire. Furthermore, the current signal of the household electricity wire captured by the signal capturing unit is transformed to a voltage signal by a second resistor R 2 . The second resistor R 2  can be a micro-resistor or a Cu (copper)-Mn (manganese) wire. 
     On the other hand, the second amplifier and rectifier unit  13  is connected to the signal capturing unit  12  for transforming the voltage signal to a second voltage wave “b”. The second amplifier and rectifier unit  13  can be a differential amplifier and full-wave/half wave rectifier circuit. In another words, the voltage (second voltage wave “b”) at the loading of first resistor RI is simulated to be a reference voltage presenting the wire is at good situation. Therefore, the difference between the first voltage wave “a” and the second voltage wave “b” is used to determine the quality of the wire. If the difference is located in a predetermined range, the wire is on a good condition. 
     The processing unit  14  is connected to the first amplifier and rectifier unit  11  and the second amplifier and rectifier unit  13  for receiving the first voltage wave “a” and the second voltage wave “b” and further comparing the first voltage wave “a” and the second voltage wave “b” so as to output a comparison result. The processing unit  14  is, but not restricted to, a MCU or an analog comparing circuit. The processing unit  14  samples and compares the two voltages. Please refer to  FIG. 4 , the figure shows the comparison result in a wave form. In  FIG. 4 , there is a negative bias between the first voltage wave “a” and the second voltage wave “b” (i.e., the reference voltage wave “b” is smaller than the first voltage wave “a”). Please refer to  FIG. 4A , the figure shows the bigger negative bias between the first voltage wave “a” and the second voltage wave “b” than that in  FIG. 4 . On other hands, there is a positive bias between the first voltage wave “a” and the second voltage wave “b” shown in  FIG. 4B . The user can determine the wire condition, for example oxidation or crack on the wire body according to the bias (positive or negative), or the difference value between the first voltage wave “a” and the second voltage wave “b”. 
     Moreover, the processing unit  14  is connected to a driving unit  16  therefore the processing unit  14  can drive the signal capturing unit  12  to capture the current signal via the driving unit  16 . 
     Additionally, the testing system for electricity safety  1  further comprises a display unit  15  for receiving and then showing the comparison result. In an embodiment, the display unit  15  has a plurality of indicating light sources with different colors and the indicating light sources are respectively turned on depending on the different comparison results. For example, the difference between the first voltage wave “a” and the second voltage wave “b” is in an “accepted range” (shown in  FIG. 4 ) and the green light source of the display unit  15  is turned on to indicate the condition of the household electricity line. If the difference out of the “accepted range” (shown in  FIG. 4A ), the red light source of the display unit  15  is turned on to warm the user that there may some defects on the wire. Alternatively, the display unit  15  can be a LCD display and the processing unit  14  can transform the comparison results with wave form into a real impedance values according a comparing table and then output the real impedance value on the LCD display. The user can directly read the impedance of the household electricity wire and further realize the condition of the wire. 
     A testing method using the testing system for electricity safety  1  is further disclosed. The testing method includes:
         step 1: inserting a testing system for electricity safety  1  in a socket  100  of the household electricity wire. The testing system for electricity safety  1  comprises a first amplifier and rectifier unit  11 , a signal capturing unit  12 , a second amplifier and rectifier unit  13 , and a processing unit  14 . Furthermore, The testing system for electricity safety  1  has a display unit  15  and a driving unit  16 .   step 2: measuring a first voltage wave “a” of the household electricity wire by the first amplifier and rectifier unit  11  when no load is applied.   step 3: capturing a current signal by the signal capturing unit  12 . In the step, the processing unit  14  can drive the signal capturing unit  12  to capture the instant current signal via the driving unit  16 .   step 4: transforming the current signal to a voltage signal by a micro-resistor and transforming the voltage signal to a second voltage wave “b” by the second amplifier and rectifier unit  13 .   step 5: comparing the first voltage wave “a” and the second voltage wave “b” and outputting a comparison result by the processing unit  14 . The comparison result is further displayed on the display unit  15  (shown in  FIGS. 4-4B ).       

     Furthermore, in order to clearly show the result of the testing method disclosed in this invention, the display unit  15  can have various display means. 
     To sum up, the present invention achieves the following advantages:
         1. In accordance with the present invention, the improved safety is achieved. The testing system for electricity safety  1  is used for directly and actively determining the impedance of the distribution wire and presenting the result clearly so that the user can clearly realize the quality of the wire.   2. The present invention is used for determining the wire quality in advance so as to improve the electricity safety.       

     Although the present invention has been described with reference to the foregoing preferred embodiment, it will be understood that the invention is not limited to the details thereof. Various equivalent variations and modifications may occur to those skilled in this art in view of the teachings of the present invention. Thus, all such variations and equivalent modifications are also embraced within the scope of the invention as defined in the appended claims.