Can't select MSSQL table

Thanks for all your support.
The config of the database and codeigniter is correct and the error was, that I have a primary database (SQLite) and the second MSSQL Database and I always tried to connect to the SQLite database.

PHP Code:

public function __construct()
  {
    $this->mssql_db = $this->load->database('lardis_mssql', TRUE);
  }

  public function get_tetra_log()
  {

  $get_where_array = array(
      "RadioID" => "******-*****-*****-****-**********"
  );

    $query = $this->mssql_db->get_where('Events', $get_where_array);
    return $query->result_array();
  }