Abstract:
A conductivity measurement method for measuring the conductivity of a fluid in a washing chamber in an electrical washing machine using a water quality sensor consisting of a control unit and first and second conductors by alternatively changing the electric potential of the first and second conductors and repeatedly measuring the conductivity of the fluid in the washing chamber between the first and second conductors upon each electric potential alternation.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to conductivity measurement technology and more particularly, to a conductivity measurement method that slows down conductor oxidation by alternatively changing the electric potential of the first and second conductors of the water quality sensor during its operation to measure the conductivity of a fluid in a washing chamber of a washing machine. 
         [0003]    2. Description of the Related Art 
         [0004]    With the rapid progress in modern technology, many advanced electrical home appliances have been continuously created for handling labor-consuming jobs, bringing both convenience and comfort to people. Among commercial electrical home appliances, washing machines such as clothes washers or dishwashers are adapted for washing objects with water and a cleaning agent, saving much washing labor and time. A clothes washer, dishwasher or any other washing machine generally has a water quality sensor installed in the internal washing chamber for detecting the quality of the fluid in the washing chamber. A water quality sensor for this purpose generally comprises a control unit, and two conductors electrically coupled in parallel to the control unit and suspending in the washing chamber for direct contact with the applied fluid. In operation, the control unit drives one conductor into HIGH and the other into LOW, enabling an electric current to be discharged out of the conductor at HIGH and conducted by the fluid in the washing chamber to the other conductor at LOW, and thus the control unit can measure the conductivity of the fluid through the two conductors. Normally, the conductivity of electrons in the fluid is constant. If ions (laundry detergent or washing powder) exist in the fluid, the conductivity of the electrons in the fluid will be changed. By means of comparing the conductivity of the fluid in the washing chamber with a predetermined reference value can check the presence of unnecessary ions in the fluid to determine whether or not to keep washing. 
         [0005]    However, when the control unit conducts the two conductors to measure the conductivity of the fluid, the applied electric current goes from one conductor through the fluid to the other conductor in one single direction, thus, conductor polarization can lead to oxidation of the conductors. Due to the effect of reduction at the conductor at LOW, the other conductor at HIGH can get rust when conducted for a certain length of time, affecting its current output strength and resulting in a conductivity measuring error and further washing determination error. An improvement in this regard is necessary. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a conductivity measurement method that slows down oxidation of the conductors of the water quality sensor when measuring the conductivity of a fluid in a washing chamber of a washing machine, assuring a high level of sensing accuracy and enabling the washing machine to accurately determine continuation of the washing process subject to the fluid state in the washing chamber. It is another object of the present invention to provide a conductivity measurement method that slows down oxidation of the conductors of the water quality sensor during the conductivity measuring operation, thereby prolonging the lifespan of the water quality sensor. 
         [0007]    To achieve these and other objects of the present invention, a conductivity measurement method for measuring the conductivity of a fluid in a washing chamber in an electrical washing machine using a water quality sensor consisting of a control unit and first and second conductors is performed by alternatively changing the electric potential of the first and second conductors and repeatedly measuring the conductivity of the fluid in the washing chamber between the first and second conductors upon each electric potential alternation. 
         [0008]    Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an oblique top elevational view of a water quality sensor in accordance with the present invention. 
           [0010]      FIG. 2  is a block diagram of the water quality sensor shown in  FIG. 1 . 
           [0011]      FIG. 3  is a flow chart of a conductivity measurement method in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]    Referring to  FIGS. 1 and 2 , a water quality sensor  1  is shown, comprising a control unit  11 , and a first conductor  12  and a second conductor  13  respectively electrically connected to the control unit  11  and suspending outside the water quality sensor  1 . The control unit  11  comprises a microcontroller  111  and a driver circuit  112 . The microcontroller  111  is electrically coupled with the driver circuit  112 . The driver circuit  112  is electrically coupled with the first conductor  12  and the second conductor  13 . Referring to  FIG. 3 , the water quality sensor  1  is used to perform a conductivity measurement method for measuring the conductivity of a fluid. The conductivity measurement method comprises the steps of:
       ( 200 ) turning on the water quality sensor  1 ;   ( 201 ) the control unit  11  driving the first conductor  12  into HIGH and the second conductor  13  into LOW;   ( 202 ) the control unit  11  measuring the conductivity of the fluid between the first conductor  12  and the second conductor  13  within a predetermined sensing period;   ( 203 ) the control unit  11  driving the first conductor  12  into LOW and the second conductor  13  into HIGH;   ( 204 ) the control unit  11  measuring the conductivity of the fluid between the first conductor  12  and the second conductor  13  within another predetermined sensing period;   ( 205 ) the control unit  11  driving the first conductor  12  and the second conductor  13  into LOW;   ( 206 ) turning off the water quality sensor  1 , and then returning to step ( 200 ) a predetermined sensing period after the water quality sensor  1  is off.       
 
         [0020]    More specifically, in the aforesaid process, the water quality sensor  1  is installed in an electrical washing machine (clothes washer or dishwasher) to suspend the first conductor  12  and the second conductor  13  in the washing chamber. When the electrical washing machine is started up, the water quality sensor  1  is turned on. At this time, the microcontroller  111  of the control unit  11  provides a control signal to the driver circuit  112 , causing the driver circuit  112  to drive the first conductor  12  into HIGH and the second conductor  13  into LOW for a predetermined sensing period and then to output an electric current through the first conductor  12  to the second conductor  13  via the fluid in the washing chamber. Within the aforesaid predetermined sensing period, the microcontroller  111  provides a sensing signal to the driver circuit  112  to detect the conductivity of the fluid between the first conductor  12  and the second conductor  13 . 
         [0021]    The driver circuit  112  of the control unit  11  is adapted for amplifying or filtrating the control signal provided by the microcontroller  111 , or to dividing the voltage of the control signal. As the driver circuit is of the known art and not within the scope of the spirit of the present invention, no further detailed description in this regard will be necessary. 
         [0022]    After the aforesaid predetermined sensing period is up, the microcontroller  111  of the control unit  11  will provide a control signal to the driver circuit  112 , causing the driver circuit  112  to drive the first conductor  12  into LOW and the second conductor  13  into HIGH for another predetermined sensing period and then to output an electric current through the second conductor  13  to the first conductor  12  via the fluid in the washing chamber. Within this secondary predetermined sensing period, the microcontroller  111  provides a sensing signal to the driver circuit  112  to detect the conductivity of the fluid between the first conductor  12  and the second conductor  13 . 
         [0023]    After the aforesaid secondary predetermined sensing period is up, the microcontroller  111  of the control unit  11  will provide a control signal to the driver circuit  112 , causing the driver circuit  112  to drive the first conductor  12  and the second conductor  13  into LOW, stopping conduction between the first conductor  12  and the second conductor  13 , and then the water quality sensor  1  is turned off. After a predetermined period, which is determined subject to the washing operation of the electrical washing machine, the aforesaid operating process is repeated. 
         [0024]    The aforesaid predetermined sensing period can be in the range of 3-30 seconds subject to the washing operation of the electrical washing machine, allowing the control unit  11  to detect the conductivity of the fluid between the first conductor  12  and the second conductor  13 . 
         [0025]    As stated above, the conductivity measurement method of the present invention is to alternatively change the electric potential of the first conductor  12  and the second conductor  13  subject to the control of the control unit  11 , slowing down oxidation of the first conductor  12  and second conductor  13  at high potential due to polarization and preventing output current instability due to rust of the first conductor  12  and second conductor  13 . Thus, the control unit  11  can accurately measure the conductivity of the fluid through the first conductor  12  and second conductor  13 , enabling the washing machine to accurately determine continuation of the washing process subject to the fluid state in the washing chamber. 
         [0026]    Further, controlling the control unit  11  of the water quality sensor  1  to alternatively change the electric potential of the first conductor  12  and second conductor  13  during the measuring process can effectively slows down oxidation of the first conductor  12  and second conductor  13 , preventing the first conductor  12  and second conductor  13  from getting rust and prolonging the lifespan of the water quality sensor  1 . 
         [0027]    In conclusion, the conductivity measurement method of the present invention has the advantages as follows: 
         [0028]    1. By means of the control unit  11  of the water quality sensor  1  to alternatively change the electric potential of the first conductor  12  and second conductor  13  during the measuring process, oxidation of the first conductor  12  and second conductor  13  at high potential is slowed down, achieving a high level of conductivity measuring accuracy. 
         [0029]    2. Controlling the control unit  11  of the water quality sensor  1  to alternatively change the electric potential of the first conductor  12  and second conductor  13  during the measuring process can prevent the first conductor  12  and second conductor  13  from getting rust and prolonging the lifespan of the water quality sensor  1 . 
         [0030]    Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.