Ph value measuring device comprising in situ calibration means

Patent metadata

Field	Value
Publication number	US-2020011830-A1
Application number	US-201816030086-A
Country	US
Kind code	A1
Filing date	Jul 9, 2018
Priority date	Jan 25, 2013
Publication date	Jan 9, 2020
Grant date	—

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.

First claim

1 - 6 . (canceled)

7 . A method of performing calibrated measurements of the pH of an effluent using a non-glass electrode probe, comprising:
placing the probe in contact with the effluent; repeatedly obtaining measurements of the pH of the effluent by, for each measurement,
biasing an ISFET transistor by applying a constant voltage and current across source and drain terminals of the ISFET, a gate terminal of which is insulated from the source and drain terminals and in contact with the effluent and hence at the same voltage as the non-glass reference electrode;
measuring a voltage V GS between the non-glass reference electrode and the ISFET source terminal;
determining the pH of the effluent from V GS and a calibration curve expressing V GS as a function of the pH of the effluent; and
periodically, while obtaining measurements of the effluent pH, performing an in situ calibration of the probe, by
modifying the pH of the effluent in the vicinity of the ISFET gate terminal and non-glass reference electrode to a first known value pH 1 ;
obtaining a corresponding value V GS1 by performing the biasing and measuring steps on the effluent at the known pH 1 ; and
calibrating the probe by modifying an intercept point E 0 in the calibration curve, using the values V GS1 and pH 1 .

8 . The method of claim 7 wherein the calibration curve is of the form
V GS =C 2 ·pH+ E 0 , where

V GS is the gate-source voltage of the ISFET obtained in the measuring step;
C 2 is a predetermined value representing the slope of the curve;
pH is the pH of the effluent; and
E 0 is a predetermined value representing the intercept point of the curve.

9 . The method of claim 8 wherein the predetermined values C 2 and E 0 are determined at manufacture by calibration using solutions of known pH.

10 . The method of claim 8 wherein modifying an intercept point E 0 in the calibration curve, using the values V GS1 and pH, comprises applying the formula:
E 0 =V GS1 −C 2 ·pH 1 .

11 . The method of claim 8 wherein performing an in situ calibration of the probe further comprises:
modifying the pH of the effluent in the vicinity of the ISFET gate terminal and non-glass reference electrode to a second known value pH 2 ;
obtaining a corresponding value V GS2 by performing the biasing and measuring steps on the effluent at the known pH 2 ; and
calibrating the probe by modifying both the intercept point E 0 and a slope value C 2 in the calibration curve, using the values V GS1 , V GS2 , pH 1 , and pH 2 .

12 . The method of claim 11 wherein modifying the values E 0 and C 2 , using the values V GS1 , V GS2 , pH 1 , and pH 2 , comprises applying the following formulas:

C
2

=

(

pH
1

-

pH
2

)

(

V

GS



1

-

V

GS



2

)




and




E
0

=

-

(

p




H
1

-

p




H
2

)

(

V

GS



1

-

V

GS



2

)

·
p





H
1

.

13 . The method of claim 7 wherein modifying the pH of the effluent in the vicinity of the ISFET gate terminal and non-glass reference electrode comprises applying a constant current I 1 between an anode surrounding, but not touching, the ISFET gate terminal, and a cathode comprising an electrode disposed in the effluent, for an adjustable duration T 1 .

14 . The method of claim 13 wherein the adjustable duration T 1 varies from 1 to 30 minutes.

Assignees

• Veolia Water Solutions & Tech

Inventors

• De Coulon Yves
• Beriet Carine
• Lemoine Cyrille

Classifications

• G01N27/302

  pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes (ion selective electrodes G01N27/333, glass electrodes G01N27/36) · CPC title

• G01N27/414 Primary

  Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS · CPC title

• G01N27/4165 Primary

  for pH meters · CPC title

• G01N27/3335 Primary

  the membrane containing at least one organic component (G01N27/3271 takes precedence; aspects concerning the enzyme reagent in enzyme electrodes C12Q1/001) · CPC title