Ph value measuring device comprising in situ calibration means

Abstract

The invention concerns a device for measuring the pH of an effluent, said device comprising means for measuring an item of information representative of the pH of said effluent intended to be brought into contact with said effluent. According to the invention, such a device further comprises means for modifying the pH value of said effluent close to said means for measuring.

1 - 15 . (canceled) 
     
     
         16 . Device for measuring the pH of an effluent, said device comprising means for measuring a piece of information representing the pH of said effluent that are to be put into contact with said effluent, and means for modifying the value of the pH of said effluent in proximity to said means for measuring,
 characterized in that it comprises means for calibrating said device for measuring, said means for calibrating being configured to calibrate the device for measuring after modification of said pH of said effluent in proximity to said means for measuring by said means for modifying.   
     
     
         17 . Device according to  claim 16 , characterized in that said means for measuring comprise:
 an ISFET type transistor comprising a source and a drain disposed on a substrate, and a gate that is to be put into contact with said effluent;   a reference electrode;   means for generating a constant voltage at the terminals of said source and said drain;   second means for generating a constant electric current between said source and said drain;   means for measuring a control voltage V GS  at the terminals of said source and said reference electrode;   means for determining the value of the pH of said effluent as a function of the value of said control voltage V GS , the value of the control voltage V GS  and the value of the pH being related by a formula of the type:
     V   GS   =C   2 ·pH+ E   0 , where E 0  and C 2  are predefined constants;
 
   
       and in that said means for calibrating are configured to implement steps of calibration during which:
 they act on said means for modifying the value of the pH to take it momentarily to at least one first known value pH 1 , then 
 they act on said means for measuring a control voltage V GS , to measure its corresponding value V GS1 ; 
 they compute the value of the constant E 0  according to the values of pH 1  and of V GS1 . 
 
     
     
         18 . Device according to  claim 17 , characterized in that said means for calibrating are configured to implement steps of calibration during which:
 they act on said means for modifying the value of the pH to take it momentarily to a first known value pH 1 , then   they act on said means for measuring a control voltage V GS , to measure the value V GS1  corresponding to the first value pH 1 ;   they act on said means for modifying the value of the pH to take it momentarily to a second known value pH 2 ; then   they act on said means for measuring a control voltage V GS , to measure the value V GS2  corresponding to the second value pH 2 ;   they compute the value of said constants E 0 , C 2  according to the known values of pH 1 , pH 2 , V GS1  and V GS2 .   
     
     
         19 . Device according to  claim 16 , characterized in that said means for modifying the value of the pH comprise an anode and a cathode to be put into contact with said effluent, and first means for generating electric current between said anode and said cathode. 
     
     
         20 . Device according to  claim 19 , characterized in that said means for modifying the pH comprise command means to implement or not implement said first means for generating an electric current 
     
     
         21 . Device according to  claim 20 , characterized in that said means for calibrating are configured to act on said command means to implement said first means for generating an electric current to modify the value of the pH during said steps of calibration. 
     
     
         22 . Device according to  claim 19 , characterized in that it comprises a membrane permeable to the H +  ions covering and being in contact with said anode and at least partly said means for measuring. 
     
     
         23 . Device according to  claim 22 , characterized in that said membrane covers said gate and said anode, said gate and said anode being in contact with said membrane. 
     
     
         24 . Device according to  claim 22 , characterized in that said membrane is made of polymer. 
     
     
         25 . Device according to  claim 24 , characterized in that said polymer is poly(2-hydroxyethylmethacrylate). 
     
     
         26 . Method for measuring the pH of an effluent by means of a device according to  claim 16 , characterized in that it comprises:
 a step for measuring the pH with said means for measuring;   a step for calibrating comprising at least one step for modifying said pH of said effluent in proximity to said means for measuring by said means for modifying, and a step for calibrating said device for measuring by said means for calibrating.   
     
     
         27 . Method according to  claim 26 , characterized in that said step for measuring the pH comprises:
 a step for generating a constant voltage at the terminals of said source and said drain;   a step for generating a constant electric current at the terminals of said source and said drain;   a step for measuring a control voltage at the terminals of said source and said reference electrode;   a step for determining the value of said pH as a function of the value of the control voltage V GS , the value of the control voltage V GS  and the value of the pH being related by a formula of the type: V GS =C 2 ·pH+E 0 , where E 0  and C 2  are predefined constants;   
       and in that said step for calibrating comprises:
 a step for modifying said pH by said means for modifying the value of the pH to take it momentarily to a first known value pH 1 , then 
 a step for measuring the corresponding control voltage V GS1  by said means ( 31 ) for measuring a control voltage; 
 a step of computation by said means for calibrating of said constant E 0  as a function of the known values pH 1  and V GS1 . 
 
     
     
         28 . Method according to  claim 27 , characterized in that said step for calibrating comprises:
 a step for modifying said pH by said means for modifying the value of the pH to take it momentarily to a first known value pH 1 , then   a step for measuring the control voltage V GS1  by said means for measuring a control voltage V GS , to measure the value V GS1  corresponding to the first value pH 1 , then   a step for modifying said pH by said means for modifying the value of the pH to take it momentarily to a second known value pH 2 ,   a step for measuring the control voltage V GS2  by said means for measuring a control voltage V GS  to measure the value V GS2  corresponding to the second value pH 2 ;   a step of computation by said means for calibrating of the value of said constants E 0 , C 2  as a function of the known values of pH 1 , pH 2 , V GS1  and of V GS2      
     
     
         29 . Method according to  claim 27 , characterized in that said step or steps for modifying said pH comprise a step for implementing said first means for generating an electrical current. 
     
     
         30 . Method according to  claim 26 , characterized in that said step for calibrating is implemented at a predetermined frequency. 
     
     
         31 . A method of measuring the pH of an effluent with a pH measuring device and periodically calibrating the pH measuring device comprising:
 engaging the effluent with a probe that forms a part of the pH measuring device;   utilizing the probe to measure a parameter that is representative of the pH of the effluent and determining the pH of the effluent as a function of the parameter; and   periodically calibrating the pH measuring device by:
 (i) adjusting the pH of the effluent in the vicinity of the probe to a known pH; 
 (ii) adjusting the function such that the parameter measured by the probe yields a measured pH that equals the known pH.