public static function getInstance()
 {
     if (!self::$appcbGenerator) {
         self::$appcbGenerator = new APPCBGenerator();
         self::$channelsList = array();
         array_push(self::$channelsList, 'CO');
         //array_push(self::$channelsList,'Ozone');
         array_push(self::$channelsList, 'Ozone(O3)');
         array_push(self::$channelsList, 'PM10');
         array_push(self::$channelsList, 'PM2.5');
         array_push(self::$channelsList, 'SO2');
         array_push(self::$channelsList, 'NO2');
         array_push(self::$channelsList, 'Pb');
         array_push(self::$channelsList, 'NH3');
         array_push(self::$channelsList, 'Benzene');
         array_push(self::$channelsList, 'Arsenic');
         array_push(self::$channelsList, 'Nickel');
         array_push(self::$channelsList, 'BenzoPyrene');
         return self::$appcbGenerator;
     }
     return self::$appcbGenerator;
 }