PPM pool sensor

Patent metadata

Field	Value
Publication number	US-9829475-B2
Application number	US-201414535523-A
Country	US
Kind code	B2
Filing date	Nov 7, 2014
Priority date	Nov 7, 2014
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A sensor including first and second electrodes can be used to determine the concentration of at least one chemical constituent in a fluid sample under test. The electrodes can be disposed in the fluid sample and a predetermined voltage can be applied to a first electrode. The voltage can cause a current to flow between the first and second electrodes through the sample, the current dependent on the concentration of the chemical constituent in the fluid sample. A sense resistor is coupled to the first electrode such that the current flowing between the electrodes flows through the sense resistor. A processor electrically isolated from the electrodes can receive data signals indicative of the voltage drop across the sense resistor and the voltage applied at the first electrode. The received signals can be used to determine the concentration of the constituent in the fluid sample.

First claim

The invention claimed is:

1. A chemical monitoring system comprising a sensor, the sensor including:
a processor;
a first electrode electrically isolated from the processor;
an adjustable power supply electrically isolated from and in communication with the processor and configured to provide a predetermined voltage at the first electrode;
a second electrode;
a sense resistor connected in series between the first electrode and the adjustable power supply;
an analog-to-digital converter (ADC) in communication with and electrically isolated from the processor, and configured to provide information to the processor regarding (i) the voltage at the first electrode and (ii) the voltage drop across the sense resistor; wherein
the processor receives the information from the ADC regarding the voltage on the first electrode, determines the voltage at the first electrode, and controls the adjustable power supply based on the determined voltage at the first electrode; and
the processor receives the information from the ADC regarding the voltage drop across the sense resistor, determines the voltage drop across the sense resistor, and, based on the determined voltage drop across the sense resistor, determines the current flowing through the sense resistor.

2. The system of claim 1 , wherein the processor is configured to determine the chlorine concentration in a fluid sample in which the first and second electrodes are inserted based on the current flowing through the sense resistor and the voltage applied to the first electrode.

3. The system of claim 2 , further comprising at least one auxiliary sensor in communication with the processor, and wherein the processor receives auxiliary data from the at least one auxiliary sensor and determining the chlorine concentration in the fluid sample is further based on the auxiliary data.

4. The system of claim 3 , wherein the at least one auxiliary sensor comprises at least one of a temperature sensor, a pH sensor, and a flow meter.

5. The system of claim 3 , wherein the at least one auxiliary sensor is powered by a galvanically isolated power source.

6. The system of claim 5 , wherein the at least one auxiliary sensor is in communication with the processor via an optical communication.

7. The system of claim 2 , wherein the adjustable power supply comprises the output of an isolation component, and wherein the adjustable power supply is adjusted by the processor adjusting the duty cycle of a signal applied to the isolation component.

8. The system of claim 7 , wherein the isolation component comprises an opto-isolator.

9. The system of claim 2 , wherein the sensor further comprises a first amplifier and a second amplifier, the first amplifier configured to output a signal to the ADC representative of the voltage on a first side of the sense resistor and the second amplifier configured to output a signal to the ADC representative of the voltage at a second side of the sense resistor, opposite the first.

10. The system of claim 9 , wherein the first and second amplifiers are powered by a single isolated and unipolar power supply.

11. The system of claim 9 , wherein an input of the second amplifier is coupled to the first electrode and the output of the second amplifier is coupled to the ADC such that the ADC receives signals representative of both the voltage at the second side of the sense resistor and the voltage at the first electrode.

12. The system of claim 2 , further comprising
a water body containing a volume of water;
a water pump configured to circulate water from the water body through components of the system;
a chemical reservoir containing a chemical; and
a chemical pump configured to dose the chemical from the chemical reservoir to the water body; wherein
the sensor is configured to receive at least a portion of the water pumped by the water pump.

13. The system of claim 12 , wherein the chemical in the chemical reservoir is one of calcium-hypochlorite and liquid bleach, and wherein the sensor is in communication with the chemical pump and is configured to operate the chemical pump based on the detected level of chlorine in the fluid sample.

14. A system comprising:
a processor;
a first electrode and a second electrode disposed in a fluid sample;
a reference power supply configured to provide a predetermined voltage at the first electrode that is galvanically isolated from the processor;
a sense resistor having a first side coupled to the reference power supply and a second side, opposite the first, coupled to the first electrode;
a comparison circuit having a first input coupled to the first side of the sense resistor and a second input coupled to the second side of the sense resistor and the first electrode, and configured to output one or more signals to the processor indicative of the voltage drop across the sense resistor and the voltage provided at the first electrode; and
a comparison power supply configured to provide electrical power to the comparison circuit; wherein
the comparison power supply is a single, unipolar power supply; and
the processor is configured to (i) adjust the voltage at provided by the reference power supply based on the one or more signals indicative of the voltage provided at the first electrode so that the voltage at the first electrode is the predetermined voltage, and (ii) determine the concentration of chlorine in the fluid sample based on the voltage drop across the sense resistor and the predetermined voltage provided to the first electrode.

15. The system of claim 14 , further comprising
a power bus, the power bus being electrically coupled to the processor;
a reference isolating element providing isolated power between the power bus and the reference power supply; and
a comparison isolating element providing isolated power between the power bus and the comparison power supply.

16. The system of claim 15 , wherein the reference isolating element comprises an opto-isolator.

17. The system of claim 16 , wherein the processor is coupled to the opto-isolator, and wherein adjusting the voltage provided at the reference power supply comprises adjusting a duty cycle of the opto-isolator in response to the one or more signals indicative of the voltage provided at the first electrode in order to maintain the first electrode at the predetermined voltage.

18. The system of claim 15 , wherein the comparison isolating element comprises a DC-DC converter.

19. The system of claim 18 , wherein the comparison circuit comprises
a first amplifier coupled to the first side of the sense resistor and being powered by the comparison power supply; and
a second amplifier coupled to the second side of the sense resistor and being powered by the comparison power supply.

20. A method for determining the concentration of chlorine in a fluid sample, comprising:
directing the fluid sample to simultaneously contact a first electrode and a second electrode;
applying a first voltage to a first side of a sense resistor, the sense resistor having a second side opposite the first, the second side being coupled to the first electrode;
detecting a second voltage at the first electrode via a processor, the processor electrically isolated from the first electrode;
adjusting the first voltage based on the detected second voltage to achieve and maintain a predetermined voltage at the first electrode;
detecting a voltage drop across the sense resistor;
determining, from the detected voltage drop across the sense resistor, the amount of curr

Assignees

• Ecolab Usa Inc

Inventors

• Howes Jr Ronald Bruce
• Kilawee Patrick Henry
• Kadlec Leonard John

Classifications

• C02F2103/42

  from bathing facilities, e.g. swimming pools · CPC title

• G01N33/182 Primary

  Specific anions in water · CPC title

• C02F1/008

  Control or steering systems not provided for elsewhere in subclass C02F · CPC title

• G01N27/49

  Systems involving the determination of the current at a single specific value, or small range of values, of applied voltage for producing selective measurement of one or more particular ionic species · CPC title

• C02F1/76

  with halogens or compounds of halogens {(C02F1/4674 takes precedence)} · CPC title