Foxcroft Equipment & Service Company's Amperometric Chlorine Analyzer's residual reading is determined by measuring the amperage produced by oxidized chlorine in the measuring cell. The amperage level is directly proportional to the level of free chlorine available in the sample stream. When reading total chlorine, the unit is actually reading converted free iodine from potassium iodine that is added to the cell for Total Chlorine readings.The cell itself is constructed such that the sample that runs through it does so at a continuous and fixed rate. Any additional flow is allowed to overflow to waste from a drain below the overflow weir. The sample stream runs down though the lower block, where it mixes with vinegar (and Potassium iodide where Total Chlorine is being analyzed), and then flows upward into the measuring cell. Within the cell, the vinegar provides pH buffering to a value of 4.0, and aids in keeping the cell clean. If Potassium Iodide is being used to read Total Chlorine, it chemically converts any free and combined chlorine residuals into free iodine, which is then read as a total chlorine reading. The cell utilizes a mixer and 150 pvc balls to ensure even chemical mix, clean the electrode and consistent readings. Very pure grades of gold and copper are used in the construction of the electrodes to enhance signal strength. Sample flow leaves the cell from the top and runs out a secondary drain to waste.