Charset for csv export

[mrzdcmps]

I have yet another issue. I am using Umlauts (ä, ö, ü) which works in the experiment when I am adding
<meta charset="utf-8" />
to the head of the page. Unfortunately, when saving the data to a csv-file the UTF-8 charset is not being used.
I tried adding the UTF-charset in the saveData function, but no luck so far.
function saveData(name, data){ var xhr = new XMLHttpRequest(); xhr.open('POST', 'save-data6.php'); xhr.setRequestHeader('Content-Type', 'application/json; charset=utf-8'); xhr.send(JSON.stringify({filename: name, filedata: data})); }
Anyone has an idea what to do? Thanks!