Time driven function in Google script - google-apps-script

Question

I am trying to download the data from a website every hour using Google script. The code is shown as below. When I manually run the function CSV_sgj, I can receive the desired information in email. But when I set the function as time driven (every hour), what I get are all #VALUE!.
I found a similar question and tried to change
var sheet = SpreadsheetApp.getActiveSheet();
to
var sheet = SpreadsheetApp.openById("0AtAYfCLk3-h7dDBnckdSZkNXbkZBLXBHV200SGtuZnc");
but it still does not work.
Many thanks in advance for help!
The full code is below.
function readRows() {
var sheet = SpreadsheetApp.getActiveSheet();
var rows = sheet.getDataRange();
var numRows = rows.getNumRows();
var values = rows.getValues();
for (var i = 0; i <= numRows - 1; i++) {
var row = values[i];
Logger.log(row);
}
};
/**
* Adds a custom menu to the active spreadsheet, containing a single menu item
* for invoking the readRows() function specified above.
* The onOpen() function, when defined, is automatically invoked whenever the
* spreadsheet is opened.
* For more information on using the Spreadsheet API, see
* https://developers.google.com/apps-script/service_spreadsheet
*/
function CSV_sgj() {
readRows();
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getRange("A1:N32");
var data = range.getValues();
var csv = "";
for (var i = 0; i < data.length; ++i) {
csv += data[i].join(",") + "\r\n";
}
var csvFiles = [{fileName:"PSI5.csv", content:csv}]
MailApp.sendEmail("xxxxxx#gmail.com", "CSV", "", {attachments: csvFiles});
}

Answer 1

When you use
var sheet = SpreadsheetApp.openById("0AtAYfCLk3-h7dDBnckdSZkNXbkZBLXBHV200SGtuZnc");
the returned value is a spreadsheet object and what you want is a sheet object...
So you have to get the sheet by its name or by its index number. I suggest you change the variable names accordingly to keep things clear :
var ss= SpreadsheetApp.openById("0AtAYfCLk3-h7dDBnckdSZkNXbkZBLXBHV200SGtuZnc");
var sheet = ss.openByName('sheet1');// or any name you use (a string)
//or by its index
var sheet = ss.getSheets()[0] ;// 0 is the index of the first sheet in the spreadsheet (integer)