(function () { if( fieldname15|r !== '' && 0 <= fieldname15 && fieldname15 <= 14 && fieldname16|r !== '' && 5 <= fieldname16 && fieldname16 <= 1000 && fieldname19|r !== '' && 5 <= fieldname19 && fieldname19 <= 1000 && fieldname20|r !== '' && 32 <= fieldname20 && fieldname20 <= 128 ){ var pH = fieldname15; var TA = fieldname16; var CH = fieldname19; var Temp = fieldname20; var TA_table = [5, 25, 50, 75, 100, 150, 200, 300, 400, 800, 1000]; var TA_values = [0.7, 1.4, 1.7, 1.9, 2.0, 2.2, 2.3, 2.5, 2.6, 2.9, 3.0]; var CH_table = [5, 25, 50, 75, 100, 150, 200, 300, 400, 800, 1000]; var CH_values = [0.3, 1.0, 1.3, 1.5, 1.6, 1.8, 1.9, 2.1, 2.2, 2.5, 2.6]; var Temp_table = [32, 37, 46, 53, 60, 66, 76, 84, 94, 105, 128]; var Temp_values = [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]; function interpolate(value, table, valueTable) { var lowerIndex = 0; for (var i = 0; i < table.length; i++) { if (table[i] < value) { lowerIndex = i; } else if (table[i] === value) { return valueTable[i]; } else { break; } } var upperIndex = Math.min(lowerIndex + 1, table.length - 1); var ratio = (value - table[lowerIndex]) / (table[upperIndex] - table[lowerIndex]); return valueTable[lowerIndex] + ratio * (valueTable[upperIndex] - valueTable[lowerIndex]); } var interpolated_TA = interpolate(TA, TA_table, TA_values); var interpolated_CH = interpolate(CH, CH_table, CH_values); var interpolated_Temp = interpolate(Temp, Temp_table, Temp_values); var CSI_value = pH + interpolated_TA + interpolated_CH + interpolated_Temp; var CSI = CSI_value - 12.1; return CSI.toFixed(2); } })()

Pool Saturation Index Calculator (LSI/CSI)