LabVIEW's "Write Delimited Spreadsheet" function, by default, writes a new file each time it is called. There are 5 inputs on the left hand side, with File Path at the top (position 1) and Error In at the bottom (position 5). Position 4 is "append to file?", with the default value being "new file:F". If you don't wire "True" to this input, you will always overwrite.
To change its behavior so that it (almost always) appends, put this function inside a While Loop with "True" wired to the Stop condition (so it runs once and exits). Put a Shift Register on the While and wire it to the "append to file?" input. Do not initialize this Shift Register. Instead, wire a True to the right-hand (output) side of the register.
Do you see what this does? The first time you bring 1D or 2D data to this "enhanced" Write Delimited function, it uses the file path (or gives you a dialog if empty), and "append to file?" is false because the Shift Register was not initialized. When it writes that first time and exits the While Loop, the Shift Register is set to "True", so all further writes will "append to file".
Bob Schor
