Tested creating new files (works!), changed order of T/RH in files
Code working. Interval set to 10s
Trying to adapt the code for 2 sensors, testing

Not working - may be because one of the Arduinos is not outputting the correct thing
Test code written to check if each chip is working (to use with scope)
Code working for both sensors
Added feature to avoid overwriting existing log files

Before creating a file & writing header row, check to see if the file exists (do not create if it does!)