Apparatus for monitoring chlorine concentration in water

1. Apparatus for monitoring chlorine in water, which apparatus comprises a flow cell, the flow cell containing a chlorine sensor and an automatic calibration system, and the automatic calibration system being such that it comprises a small pair of in-line electrodes for generating low concentrations of free chlorine, and injection means for injecting in use of the apparatus a salt solution of known concentration.

2. Apparatus according to claim 1 in which the salt solution is a buffered salt solution.

3. Apparatus according to claim 2 in which the buffered salt solution is a phosphate buffered salt solution.

4. Apparatus according to claim 1 in which the salt solution is un-buffered.

5. Apparatus according to claim 1 in which the small pair of in-line electrodes is such that each electrode is a 4.5 mm square printed platinum electrode on an inert sintered alumina substrate, mounted on a plastics body for integration in to the flow cell.

6. Apparatus according to claim 1 and including temperature measuring means.

7. Apparatus according to claim 1 and including conductivity measuring means.

8. Apparatus according to claim 1 and including pH measuring means.

9. Apparatus according to claim 1 and including Redox measuring means.

10. Apparatus according to claim 1 in which the electrodes are made from inert metal, rare earth metal oxide, or precious metal.

11. Apparatus according to claim 1 in which the electrodes are microprocessor controlled for constant current or constant voltage.

12. Apparatus according to claim 1 in which the electrodes are a pair of similar electrodes that, with periodic polarity reversal, are self-cleaning.

13. Apparatus according to claim 1 in which the electrodes are easily replaceable, with the same mounting configuration as the sensors in the apparatus.

14. Apparatus according to claim 1 in which the calibration system comprises a calibration chamber, agitation means in the chamber, and sample control valves for permitting recirculation of a sample past the sensors during the chlorination process.

15. Apparatus according to claim 14 in which the agitation means is a stirrer or a pump.

16. Apparatus according to claim 1 in which the calibration system includes a calibration chamber which includes means for reducing the free chlorine concentration.

17. Apparatus according to claim 1 and including input means for adding other solutions to aid in calibration.

18. Apparatus according to claim 1 and including optical sensors in the apparatus.

19. Apparatus according to claim 1 and including at least one of (i) an internal battery or a range of power inputs to facilitate installation in a wide range of locations, and (ii) a microprocessor with display and keypad, or a touch-sensitive screen.

20. Apparatus according to claim 1 in which the apparatus is portable, and in which the apparatus includes a self-priming pump.