Amperometric sensor probe for an automatic halogen control system

Abstract

An amperometric bromine control system accurately maintains a desired concentration of bromine within a home spa or in other water features. The control system employs amperometric sensing to measure the bromine concentration in the spa water and uses this measurement to control the electrochemical production of bromine through the oxidation of aqueous bromide. The level of bromide in the spa water desirably is greater than 50 ppm in order to obtain a linear relationship between the current level sensed through the amperometric measurement and the concentration level of bromine in the water. In this manner, the control system can accurately measure the bromine concentration in the spa water and precisely maintain the bromine concentration within a desired range between about 2 ppm and 6 ppm.

What is claimed is:  
     
         1 . An amperometric sensor probe comprising: 
 a housing;    a working electrode and a counter electrode, each electrode having a portion which is exposed relative to the housing at a working end;    a reference electrode immersed in an electrolyte and positioned within the housing;    a junction arranged between the electrolyte and an exterior of the working end to allow ionic communication between the working end exterior and the electrolyte;    a memory device positioned within the housing; and    a data port, said data port being connected to said memory device and to said electrodes.    
     
     
         2 . The sensor probe of  claim 1 , wherein the memory is an electrically erasable programmable ROM.  
     
     
         3 . The sensor probe of  claim 2 , wherein the memory device stores data that is specific for the sensor probe.  
     
     
         4 . The sensor probe of  claim 3 , wherein the data specific for the sensor probe represents a current response being caused by this sensor probe and being indicative of a concentration of a chemical species in water, said current response defining a preset parameter when connected to a control system.  
     
     
         5 . The sensor probe of  claim 1 , wherein said junction comprises a porous membrane occupying an opening in the housing on the working end.  
     
     
         6 . The sensor probe of  claim 1 , wherein the exposed portions of the working and counter electrodes lie adjacent to each other.  
     
     
         7 . The sensor probe of  claim 1 , wherein the working and counter electrodes are comprised of a carbon-based material.  
     
     
         8 . A method for a determining measurement characteristic of a sensor probe, comprising the steps of: 
 providing a sensor probe with a memory device;    placing the sensor probe into a known environment;    determining a measurement characteristic of the sensor probe when placed into said known environment; and    storing in said memory device the measurement characteristic of the sensor probe.    
     
     
         9 . The method of  claim 8 , further comprising the step of providing an aqueous solution as the known environment for the sensor probe, said aqueous solution having a known concentration of a chemical species.  
     
     
         10 . The method of  claim 9 , further comprising the step of determining a current response of the sensor probe when brought into contact with the aqueous solution.  
     
     
         11 . The method of  claim 10 , wherein storing said measurement characteristic includes storing the current response associated with the known concentration of the chemical species in the aqueous solution.  
     
     
         12 . The method of  claim 11 , further comprising the steps of calculating additional current responses associated with other corresponding concentrations of the chemical species based on the aqueous solution of known concentration, and storing in the memory device each calculated current response for a corresponding concentration of the chemical species in an aqueous solution.  
     
     
         13 . The method of  claim 12 , wherein calculating said additional current responses involves extrapolating said calculated current responses using at least said determined current responses.  
     
     
         14 . The method of  claim 12 , wherein calculating said additional current responses involves interpolating said calculated current responses using at least said determined current responses.  
     
     
         15 . The method of  claim 11 , further comprising the steps of: 
 providing a second aqueous solution of a known second concentration of a chemical species;    bringing the sensor probe into contact with the second aqueous solution;    determining a second current response of the sensor probe at said known second concentration;    storing in the memory device the second current response associated with the second concentration of the chemical species in the second aqueous solution.    
     
     
         16 . The method of  claim 15 , further comprising the steps of calculating additional current responses associated with other corresponding concentrations of the chemical species based on the aqueous solution, and storing in the memory device each calculated current response for a corresponding concentration of the chemical species in an aqueous solution.  
     
     
         17 . The method of  claim 16 , wherein calculating said additional current responses involves extrapolating said calculated current responses using at least said both determined current responses.  
     
     
         18 . The method of  claim 16 , wherein calculating said additional current responses involves interpolating said calculated current responses using at least said both determined current responses.  
     
     
         19 . In combination, a water feature containing water, and an amperometric sensor probe in contact with the water of the water feature, the sensor probe comprising: 
 a housing;    a working electrode and a counter electrode, each electrode having a portion which is exposed relative to the housing at a working end;    a reference electrode immersed in an electrolyte and positioned within the housing; and    a junction arranged between the electrolyte and exteriors of the working ends to allow ionic communication between the working end exteriors and the electrolyte.    
     
     
         20 . The combination of  claim 19 , wherein said junction comprises a porous membrane occupying an opening in the housing on the working end.  
     
     
         21 . The combination of  claim 19 , wherein the exposed portions of the working and counter electrodes lie adjacent to each other.  
     
     
         22 . The combination of  claim 19 , wherein the working and counter electrodes are comprised of a carbon-based material.  
     
     
         23 . The combination of  claim 19 , wherein the reference electrode comprises a silver/silver chloride wire.  
     
     
         24 . The combination of  claim 19 , additionally comprising an electrical connector located on a side of the housing opposite of the working end.  
     
     
         25 . The combination of  claim 24 , wherein said housing has an elongated, tubular body extending between the working end and the end on which the electrical connector is disposed.  
     
     
         26 . The combination of  claim 24 , additionally comprising shielded conductors which couple said working and counter electrodes, which are located at the working end of the housing, to the electrical connector, which is on the opposite side of the housing.  
     
     
         27 . The combination of  claim 26 , additionally comprising a printed circuit board mounted within the housing, said electrical connector being attached to a side of the board facing away from the working end, and said shielded conductors connected to the board on an opposite side, said printed circuit board connecting said shielded conductors to the electrical connector.  
     
     
         28 . The combination of  claim 27 , wherein said housing includes a cap attached to an end of the tubular body near the electrical connector, and said printed circuit board being attached to said cap.  
     
     
         29 . The combination of  claim 27 , wherein said reference electrode is connected to the printed circuit board which interconnects said electrical connector and said reference electrode.  
     
     
         30 . The combination of  claim 19 , additionally comprising a pH electrode having a portion which is exposed relative to the housing at the working end.  
     
     
         31 . The combination of  claim 19 , wherein the housing comprises an end plug having at least three openings, a first of the openings receiving the working electrode, a second of the openings receiving the counter electrode, and the third of the openings receiving the junction, and the electrodes being potted within the end plug.  
     
     
         32 . The combination of  claim 31 , wherein the end plug lies at proximate to the working end of the housing so as to position the working and counter electrodes at the working end, and the housing includes an external thread extending about the end plug.  
     
     
         33 . A method for automatically maintaining the concentration of a sanitizing agent in a water feature within a preset range using an automatic sanitizing system, comprising the steps: 
 providing an aqueous solution with a sanitizing agent in the water feature;    providing an amperometric sensor probe including at least a reference electrode and a working electrode;    placing at least a portion of the working electrode in contact with the aqueous solution;    maintaining a generally constant preset voltage between the electrodes;    measuring a current through the working electrode which is indicative of the concentration of the sanitizing agent within the aqueous solution; and    using the measured current to maintain the concentration of the sanitizing agent in the aqueous solution within the preset range.    
     
     
         34 . The method of  claim 33 , additionally comprising producing a flow of aqueous solution over said working electrode before measuring the current.  
     
     
         35 . The method of  claim 33 , additionally comprising preforming diagnostic checks of at least some components of the automatic sanitizing system when producing the aqueous flow over said working electrode before taking the current measurement.  
     
     
         36 . The method of  claim 33 , additionally comprising electrochemically producing the sanitizing agent when the measured current is below a preset range.  
     
     
         37 . The method of  claim 36 , wherein electrochemically producing the sanitizing agent comprises providing an electrolyte within the aqueous solution and circulating a portion of the aqueous solution through an electrolytic cell.  
     
     
         38 . The method of  claim 37 , additionally comprising energizing the electrolytic cell when the measured current is below the preset range.  
     
     
         39 . The method of  claim 38 , additionally comprising clocking a cumulative operating time of the electrolytic cell, determine when the cumulative operating time exceeds a preset duration, and cleaning the electrolytic cell when the cumulative operating time exceeds the preset duration.  
     
     
         40 . The method of  claim 37 , additionally comprising operating the electrolytic cell in a deenergized mode when the measured current is above the preset range.  
     
     
         41 . The method of  claim 37 , additionally comprising: 
 controlling the operation of the electrolytic cell over a series of consecutive duty cycles;    determining whether the electrolytic cell was energized during at least a portion of the immediately preceding duty cycle; and    energizing the electrolytic cell when the measured current is within the present range and the electrolytic cell was energized during at least a portion of the immediately preceding duty cycle.    
     
     
         42 . The method of  claim 37 , additionally comprising: 
 controlling the operation of the electrolytic cell over a series of consecutive duty cycles;    determining whether the electrolytic cell was energized during at least a portion of the immediately preceding duty cycle; and    operating the electrolytic cell in a deenergized mode when the measured current is within the present range and the electrolytic cell was not energized during any portion of the immediately preceding duty cycle.    
     
     
         43 . The method of  claim 33 , wherein maintaining the voltage between the reference electrode and the working electrode involves providing a counter electrode coupled to the reference electrode such that the reference electrode provides a feedback signal to the counter electrode.  
     
     
         44 . The method of  claim 43 , additionally comprising applying a sequence of three different references voltages between said working electrode and said counter electrode during a cleaning cycle.  
     
     
         45 . The method of  claim 44 , wherein at least one negative potential and at least one positive potential are applied during the cleaning cycle.  
     
     
         46 . The method of  claim 44 , wherein said cleaning cycle comprises a cleaning step of applying a reference voltage of +1 volts for one minute between the working and counter electrodes, applying a reference voltage of −80 millivolts for one minute between the working and counter electrodes, and applying a reference voltage of +300 millivolts between the working and counter electrodes.  
     
     
         47 . The method of  claim 46 , wherein the cleaning step is performed in the following sequence: applying a positive potential between the working and counter electrodes; applying a negative potential between the working and counter electrodes; and applying a positive potential between the working and counter electrodes.  
     
     
         48 . The method of  claim 46 , wherein the cleaning step is performed at least five times during the cleaning cycle.  
     
     
         49 . The method of  claim 44 , additionally comprising applying a fourth reference voltage between the counter electrode and the working electrode with the fourth reference electrode corresponding to a reduction potential of a chemical species other than the sanitizing agent being measured.  
     
     
         50 . The method of  claim 43 , wherein maintaining the voltage between the reference electrode and the working electrode additionally involves providing a potentiostat coupled to the working, counter and reference electrodes, said potentiostat including a plurality of operational amplifiers.  
     
     
         51 . The method of  claim 50 , additionally comprising applying asymmetric power to at least one of the operational amplifiers.  
     
     
         52 . The method of  claim 51 , wherein a positive voltage of about +5 volts and a negative voltage in the range of about −4.2 volts to about −4.5 volts is applied to the at least one operational amplifier.  
     
     
         53 . A method of cleaning a first electrode of a probe, with the probe including at least the first electrode and a second electrode, comprising applying a sequence of three different references voltages between said first and second electrodes.  
     
     
         54 . The method of  claim 53 , wherein at least one negative potential and at least one positive potential are applied between the electrodes as two of the three reference voltages.  
     
     
         55 . The method of  claim 53 , wherein applying the sequence of three different reference voltages involves applying a reference voltage of +1 volts for one minute between the electrodes, applying a reference voltage of −80 millivolts for one minute between the electrodes, and applying a reference voltage of +300 millivolts between the electrodes.  
     
     
         56 . The method of  claim 55 , wherein the reference voltages are applied in the following sequence: applying a positive potential between the electrodes; applying a negative potential between the electrodes; and applying a positive potential between the electrodes.  
     
     
         57 . The method of  claim 56 , wherein the sequence is performed at least five times.