This is a known issue with Logger pro version Saving a file with the Vernier Emissions Spectrometer (VSP-EM) connected and reopening the file will inadvertently and incorrectly set the spectrometer collection mode to transmittance. It also enables other collection modes to be selected for the spectrometer in software setup. When you attempt to collect, the software detects the mode is not intensity and complains that the spectrometer must be calibrated.

You may work around the issue by accessing the “rainbow” menu in the spectrometer setup dialog (accessed from the live readouts bar at the upper left of Logger Pro) and reset the mode to intensity. This allows further collection to take place using the opened file avoiding the erroneous calibration message. No calibration is actually needed.