Thank you for your help, I tried to connect the read value + the new data in the write value as you did but it didnt work.
You need to configure the built array to "concatenate mode". Still, the value property node suggestion is absolutely horrible. Don't do it!
I'll try to make a better example later...
OK, first of all, you need to show us your code, because there are many ways to do multiple measurements. We also don't know your LabVIEW version.
The solution is always the same: Keep the current plots in a shift register and append the new plot, then update the graph. Here's one possibility:
OTOH, of you want to append to the same plot, but just create a gap, include a NaN values between plots.