Hi Paul i read up to 32 values per second. i prefer to put the 32 values in a string and then
write the string to the SD Card.
i read in the tutorial that dataString += "," is the same like dataString = dataString + ",";
buth with dataString += "," i have the problem and with dataString = dataString + ","; it works well.
must i calculate with more bugs like this in Arduino ? 
Greetings John