display 4 and key pad 5 the pool water 2 temperature is measured by a temperature probe 6 submerged in the water the temperature probe is connected to the computer 39 s analog input 7 one digital output 8 is used as an on off switch for the dispensing pump 9 with its chlorine container 10 the remote display 11 can be placed at a convenient location during all weather conditions over a period of three years careful notes were kept of pool water temperature of chlorine ppm levels of quantities of chlorine added to the swimming pool and algae conditions the table shows the empirically derived units of volume of chlorine that must be added into the pool at different water temperatures in order to keep the chlorine ppm content within the recommended levels in the table at approximately 35 000 gallons one unit of volume represents 0 1 gallon of chlorine at 17 500 gallons one unit of volume represents half as much 0 05 gallon at 25 u00b0 c a 35 000 gallon pool requires 0 44 gallon of chlorine and a 17 500 gallon pool requires 0 22 gallons the differences in chlorine requirements at different temperatures illustrate the influence of varied factors such as use of the pool biological activity sunshine and weather for example at 20 u00b0 c the difference per degree c change is 0 2 units of volume at 30 u00b0 c the difference is 0 6 units of volume the table unit values are converted by.