Abstract: An apparatus measures chlorine content of a solution. The apparatus comprises a colorimeter configured to measure the chlorine content and output a first signal; an electrochemical sensor configured to measure the chlorine content and output a second signal; and a processing system configured to receive the first signal and the second signal and output a measurement of the chlorine content using at least one of the first signal and the second signal.

Abstract: Sensor and Measurement Method A turbidity sensor and method of measuring turbidity is provided. The turbidity sensor (100) comprises first and second optical detectors for detecting a respective optical response of each optical signal. The first optical detector (20) may be arranged in direct view of the emitter (10) and the second optical detector (30) may be arranged in indirect view of the emitter (10). The two detectors collect light emitted from the emitter (10) when directed through a fluid sample during two optical tests run in very close succession. Firstly, a control sample is illuminated to determine a calibration factor for the control sample with known turbidity. Then, the calibration factor is used to determine the turbidity of a fluid sample with unknown turbidity. Advantageously, background radiation during the data collection process is ignored because the transient behaviour during each optical test is negligible.

Abstract: Sensor and Measurement Method A turbidity sensor and method of measuring turbidity is provided. The turbidity sensor (100) comprises first and second optical detectors for detecting a respective optical response of each optical signal. The first optical detector (20) may be arranged in direct view of the emitter (10) and the second optical detector (30) may be arranged in indirect view of the emitter (10). The two detectors collect light emitted from the emitter (10) when directed through a fluid sample during two optical tests run in very close succession. Firstly, a control sample is illuminated to determine a calibration factor for the control sample with known turbidity. Then, the calibration factor is used to determine the turbidity of a fluid sample with unknown turbidity. Advantageously, background radiation during the data collection process is ignored because the transient behaviour during each optical test is negligible.

Abstract: An electrochemical sensor apparatus and electrochemical sensing method within an aqueous system are described, using one or more working electrodes of boron doped diamond (BDD). A cathodic reduction process provides a cathodic measurement and, substantially simultaneously, an anodic oxidation process provides an anodic measurement. A sum of a content of two equilibrium species within the aqueous system is obtained using both the cathodic measurement and the anodic measurement. One example measures total free chlorine by simultaneously measuring hypochlorous acid (HOCl) and hypochlorite ion (OCl?).