One way is to build a waveform data type with Build Waveform function,
add t0 and dt info, and use the Export Waveforms to Spreadsheet
function. The dt, (delta time) should be readily available from the
sampling rate of your data acquisition. You could also create an array
of time values, append this array to your Y array for a 2D array and
use the 2D input of Write to Spreadsheet file. There is a function in
LabVIEW called WDT Get Waveform Time Array that shows how to create an
array of time values.
