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EP-4740005-A1 - METHOD FOR MEASURING THE ELECTRICAL CONDUCTIVITY OF A FLUID AND RELATED ELECTRONIC MEASURING APPARATUS

EP4740005A1EP 4740005 A1EP4740005 A1EP 4740005A1EP-4740005-A1

Abstract

The invention relates to a method (700) and an electronic apparatus (500) for measuring the electrical conductivity of a fluid crossing a conduit (2). Such an electronic measuring apparatus (500) comprises: • - an electronic module (Ml) comprising: • - an electronic processing unit (501), • - a block (502) for detecting the electrical fluid conductivity operatively associated with the electronic processing unit; • - a first (6) and a second (7) metal electrode connected to the block for detecting the electrical fluid conductivity through a first (13) and a second (14) electrical connection, respectively; such first and second electrodes are insertable into the conduit to be in contact with the fluid; • - a temperature probe (20) connected to the electronic module through a third electrical connection (20') to provide the electronic processing unit with temperature information (SG2) associated with the fluid crossing the conduit. The method comprises the steps of: • - applying (701) a measurement potential difference between the first and second electrodes to generate a current signal (11) to be provided at the input of the electrical conductivity detection block; • - generating (702), by the electrical conductivity detection block, a first analog signal (SG1) representative of the conductivity of the fluid crossing the conduit; such a first analog signal is a periodic signal having a first frequency (f1); • - providing (703) the electronic processing unit with the first analog signal (SG1); • - processing (704) the first analog signal (SG1) to obtain the value of the first frequency of the periodic signal; • - calculating (705), by the electronic processing unit, a value of equivalent resistance (R*) associated with the fluid between the first and second electrodes from the first frequency obtained; • - providing (706), by the temperature probe, the electronic processing unit with the temperature information of the fluid crossing the conduit; - calculating (707), by the electronic processing unit, a value of electrical fluid conductivity based on said calculated value of equivalent resistance and such temperature information.

Inventors

  • Ravazzoni, Flavio
  • BOCHKO, Bogdan

Assignees

  • Silver S.n.c. di Ravazzoni Flavio e Porcelli Michele

Dates

Publication Date
20260513
Application Date
20240628

Claims (13)

  1. 1. A method (700) for measuring the electrical conductivity of a fluid crossing a conduit (2) by means of an electronic measuring apparatus (500) , said electronic measuring apparatus (500) comprising: - an electronic module (Ml) comprising: - an electronic processing unit (501) , - a block (502) for detecting the electrical fluid conductivity operatively associated with the electronic processing unit (501) ; - a first (6) and a second (7) metal electrode connected to said block (502) for detecting the electrical fluid conductivity through a first (13) and a second (14) electrical connection, respectively, said first (6) and second (7) electrodes being insertable into said conduit (2) to be in contact with the fluid; - a temperature probe (20) connected to the electronic module (Ml) through a third electrical connection (20' ) to provide said electronic processing unit (501) with temperature information (SG2) associated with the fluid crossing the conduit (2) , said method (700) comprising the steps of: applying (701) a measurement potential difference between said first (6) and second (7) electrodes in contact with said fluid to generate a current signal (II) to be provided at the input of the electrical conductivity detection block (502) ; generating (702) , by said electrical conductivity detection block (502) , a first analog signal (SGI) representative of the conductivity of the fluid crossing the conduit (2) , said first analog signal (SGI) being a periodic signal having a first frequency (fl) ; providing (703) said electronic processing unit (501) with said first analog signal (SGI) ; processing (704) , by the electronic processing unit (501) , said first analog signal (SGI) to obtain the value of said first frequency (fl) of the periodic signal ; calculating (705) , by the electronic processing unit (501) , a value of equivalent resistance (R*) associated with the fluid between the first (6) and second (7) electrodes from the first frequency (fl) obtained; providing (706) , by said temperature probe (20) , the electronic processing unit (501) with said temperature information (SG2) of the fluid crossing the conduit ( 2 ) ; calculating (707) , by the electronic processing unit (501) , a value of electrical fluid conductivity based on said calculated value of equivalent resistance (R*) and said temperature information (SG2) .
  2. 2. A method (700) for measuring the conductivity of a fluid according to claim 1, wherein said electronic module (Ml) further comprises a fluid temperature detection block (503) connected to said temperature probe (20) and operatively associated with the electronic processing unit (501) , said step (706) of providing a temperature information (SG2) of the fluid comprising the further steps of: generating, by said temperature detection block (503) , a second analog signal (SG2) representative of the temperature of the fluid crossing the conduit (2) , said second analog signal (SG2) being a periodic signal having a second frequency (f2) ; providing said electronic processing unit (501) with said second analog signal (SG2) .
  3. 3. A method (100) for measuring the conductivity of a fluid according to claim 1 or 2, wherein said provision step (703) comprises a step of performing an analogdigital conversion of said first analog signal (SGI) to generate a first digital signal to be provided to the electronic processing unit (501) .
  4. 4. A method (100) for measuring the conductivity of a fluid according to claim 2 or 3, wherein said provision step comprises a step of performing an analog-digital conversion of said second analog signal (SG2) to provide a second digital signal to the electronic processing unit (501) .
  5. 5. A method (100) for measuring the conductivity of a fluid according to any one of the preceding claims, wherein said first analog signal (SGI) and/or said second analog signal (SG2) are square wave signals.
  6. 6. A method (100) for measuring the conductivity of a fluid according to any one of the preceding claims, wherein said first frequency (fl) of the first analog signal (SGI) varies as the value of said equivalent resistance (R*) associated with the fluid between the first (6) and second (7) metal electrodes varies.
  7. 7. A method (100) for measuring the conductivity of a fluid according to the preceding claim, wherein said block (502) for detecting the electrical fluid conductivity comprises a circuit block having a respective input resistance (Rin) and an input capacitance (Cl) connected to said equivalent resistance (R*) of the fluid through said first (13) and second (14) electrical connections of the first (6) and second (7) metal electrodes, said step (705) of calculating the value of equivalent resistance (R*) is performed according to the equation: Rtot*Cl l/2nfl where: Cl is the value of the input capacitance of the electrical conductivity detection block (502) ; Rtot is the value of overall resistance obtained from the connection in parallel between the equivalent resistance (R*) of the fluid and said input resistance (Rin) of the electrical conductivity detection block (502) ; fl is the first frequency of the first analog signal (SGI) .
  8. 8. A method (100) for measuring the conductivity of a fluid according to any one of claims 2, 4-5, wherein said second frequency (f2) of the second analog signal (SG2) varies as the temperature value of the fluid crossing the conduit (2) varies.
  9. 9. A method (100) for measuring the conductivity of a fluid according to any one of the preceding claims, wherein said step (707) of calculating an electrical fluid conductivity value comprises a step of compensating for the calculated conductivity value based on the difference between the temperature value of the fluid crossing the conduit (2) associated with said temperature information (SG2) provided by the temperature probe (20) and a standard temperature value.
  10. 10. An electronic apparatus (500) for measuring the electrical conductivity of a fluid crossing a conduit (2) , comprising: an electronic module (Ml) comprising: an electronic processing unit (501) , - a block (502) for detecting the electrical fluid conductivity operatively associated with the electronic processing unit (501) ; - a first (6) and a second (7) metal electrode connected to said block (502) for detecting the electrical fluid conductivity through a first (13) and a second (14) electrical connection, respectively, said first (6) and second (7) electrodes being insertable into said conduit (2) in contact with the fluid; - a temperature probe (20) connected to the electronic module (Ml) through a third electrical connection (20' ) to provide said electronic processing unit (501) with temperature information (SG2) associated with the fluid crossing the conduit (2) , said apparatus (500) being configured to carry out the method (700) according to any one of claims 1 to 9.
  11. 11. An electronic apparatus (500) according to claim 10, wherein said electronic module (Ml) further comprises a fluid temperature detection block (503) connected to said temperature probe (20) and operatively associated with the electronic processing unit (501) .
  12. 12. An electronic apparatus (500) according to claim 10 or 11, wherein said block (502) for detecting the electrical fluid conductivity comprises: - a first operational amplifier (0A1) connected between a power supply potential terminal (VDD) and a ground potential terminal (GND) ; a first (Tl) and a second (T2) input terminal connected to said first (6) and second (7) metal electrodes, respectively, and a first output terminal (OUT1) ; - a first (Rl) and a second (R2) resistor, wherein said first resistor (Rl) is connected between a non-inverting terminal (+) of the first operational amplifier (0A1) and the ground potential terminal (GND) , and the second resistor (R2) is connected between said non-inverting terminal and the power supply potential terminal (VDD) ; - a block resistor (R6) connected between an output (01) of the first operational amplifier (0A1) and the first output terminal (0UT1) ; a resistor (R5) for charging and discharging a capacitor (Cl) placed at the input of said block (502) , said charging and discharging resistor (R5) being connected between the output terminal (01) of the first operational amplifier (0A1) and the second input terminal (T2) , said capacitor (Cl) being connected between the second input terminal (T2) and the ground potential terminal (GND) ; a safety resistor (R7) connected between the charging and discharging resistor (R5) and the first input terminal (Tl) of the block (502) ; - a start oscillation resistor (R4) connected between the second input terminal (T2) and the inverting terminal (-) of the first operational amplifier (OA1) ; a compensation resistor (R3) connected between the output terminal (01) of the first operational amplifier (OA1) and the non-inverting terminal ( + ) of said amp 1 i f i e r .
  13. 13. An electronic apparatus (500) according to claim 11 or 12, wherein said fluid temperature detection block (503) comprises: - a second operational amplifier (OA2) connected between a power supply potential terminal (VDD) and a ground potential terminal (GND) ; - an additional charging and discharging resistor (R41) of an additional capacitor (CH) , said charging and discharging resistor (R41) being connected between an output terminal (OUT2) of the block (503) and an inverting terminal (-) of the second operational amp 1 i f i e r ( OA2 ) ; - said additional capacitor (Cn) connected between the inverting terminal (-) of the second operational amplifier (OA2) and the ground potential terminal (GND) ; a feedback resistor (R31) connected between a non- inverting terminal (+) of the second operational amplifier (0A2) and said output terminal (OUT2) ; - an additional first resistor (Rn) connected between the power supply terminal (VDD) of the block (503) and the non-inverting terminal (+) of the second operational amp 1 i f i e r ( OA2 ) ; - an additional second resistor (R21) connected between the non-inverting terminal (+) of the second operational amplifier (OA2) and said ground terminal (GND) .

Description

METHOD FOR MEASURING THE ELECTRICAL CONDUCTIVITY OF A FLUID AND RELATED ELECTRONIC MEASURING APPARATUS TECHNOLOGICAL BACKGROUND OF THE INVENTION Field of application The present invention generally relates to systems for checking the electrical conductivity of a fluid . In particular, the invention relates to an innovative method for measuring the electrical conductivity of a fluid, such as water, for example . The invention also relates to an electronic measuring apparatus implementing the aforesaid method . Prior art As is known, a conductivity sensor measures the ability of a fluid or a solution to conduct electric current . It is the presence of ions to make a solution conductive : the greater the concentration of ions , the greater the conductivity . Known conductivity sensors are designed to monitor pure water in chemical processes and pharmaceutical production . These conductivity sensors provide accurate and reliable measurements to ensure process control and conformity . The most widespread conductivity sensors provide for the employment of a T- fitting inserted along a conduit in which the fluid flows , e . g . , water . Such a T- fitting comprises two doors which are on the same axis as the conduit in which the fluid flows , and a third door is orthogonal to such a conduit axis . Such a third door is configured to allow the insertion of a probe into the flow of water flowing in the conduit . The aforesaid probe consists of a pair of test electrodes connected to an electronic circuit adapted to detect contaminants in water by measuring the electrical conductivity or resistivity of the water itsel f between the two electrodes . Indeed, the conductivity of water is directly proportional to the amount of ioni zable dissolved solids , such as minerals , normally present in impure water . The purity level of water is obtained by comparing the measured conductivity value with a preset reference conductivity value . For example , i f the measured conductivity falls below the reference value , the water has an acceptable purity level and can be employed for the intended purposes . On the other hand, i f the measured conductivity exceeds the reference value , this suggests that water is contaminated to the point of not being usable for the intended purposes . However, the known methods for measuring the conductivity of water employing, for example , the above- mentioned conductivity sensors with a T- fitting, have limitations and drawbacks . Indeed, the electronic measuring circuit connected to the test electrodes immersed in the flow of water is configured to acquire an analog signal through such electrodes . Such an analog signal is representative of the conductivity of water between the two electrodes . However, the aforesaid analog signal can be highly af fected by oscillations in the voltage supplied to the electronic measuring circuit . Such oscillations can cause signi ficant variations in the amplitude of the measured analog signal , which can compromise the detection reliability for values of conductivity to be measured which are less than 5pS/cm . Moreover, the need to process the analog signal acquired requires for such a signal to first be converted into a digital signal through a respective analog-digital conversion block (Analog to Digital Converter or ADC ) . Such an ADC block can introduce further disturbances on the acquired signal caused by di f ferent calibrations between the ADC channels of the logic architectures and by the maximum resolution of the ADC converter employed . Therefore , the maximum resolution obtainable when measuring the conductivity of water with the known methods is often inadequate for many applications . SUMMARY OF THE INVENTION Therefore , it is the obj ect of the present invention to provide a method for measuring the electrical conductivity of a fluid, such as water, for example , having properties such as to at least partially obviate the drawbacks described with reference to the currently employed conductivity measurement methods of the known type . This and other obj ects are achieved by a method for measuring the electrical conductivity of a fluid according to claim 1 . The present invention also relates to an electronic measuring apparatus configured to implement the aforesaid method according to claim 10 . Preferred and advantageous embodiments of the method for measuring the conductivity of a fluid and the related electronic measuring apparatus are the subj ect of the dependent claims . BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the method and apparatus for measuring the electrical conductivity of a fluid according to the invention wil l become apparent from the following description of preferred embodiments thereof , given by way of non-limiting indication, with reference to the accompanying drawings , in which : Figure 1 shows an exploded front perspective view of an embodiment of a sensor for measuring the conductivity