Chemical sensing apparatus having multiple immobilized reagents

An at least one sensor system coupled to a pool, spa, or water feature water treatment system having water flowing within the water treatment system, the sensor system comprising:

• an at least one housing
• an electronic section containing at least one light source, at least one controller;
• at least one sensor;
• an at least one immobilized reagent target;
• an at least one sensor sensing energy incident on or through the at least one immobilized reagent target, wherein the at least one light emits an energy with specific known optical profile which is then incident on the at least one immobilized reagent target which is in contact with the water from the water treatment system and the immobilized reagent interacts with the water sample to produce a reaction in or on the at least one immobilized reagent target which changes the energy profile on the at least one immobilized reagent target, the changes are then detected by the at least one sensor sensing energy incident on or through the at least one immobilized reagent target.

A method of sensing a reactant in a body of water, comprising the steps of:

• directing a sample of water from a body of water into a housing having an at least one detection targets with an immobilized reagent thereon;
• directing an at least one light source incident upon the at least one detection targets having immobilized reagents thereon;
• emitting energy from the at least one light source incident upon the at least one detection targets having immobilized reagents thereon such that the energy changes with any interaction the immobilized reagents have with the sample;
• detecting a change in the energy incident upon the at least one detection targets having immobilized reagents caused by the interaction of the immobilized reagents with the sample of water;
• and
• reporting the results of the detection step.