We use a single wavelength detector with a spectral range 180 to 680 nm. You can set up any wavelength in that range and do measurements at that wavelength. All cannabinoids are measured at 220nm regardless of the type of UV detector. While PDA/DAD detectors can scan multiple wavelengths at the same time, those having HPLCs with PDA/DAD detectors measuring cannabinoids still do it at a single wavelength of 220nm.
With our HPLC, if you are interested in a UV spectrum of a specific compound, you can do a spectral scan from 180 to 680 nm. The detector will run through the wavelengths in 1nm increments and will plot the UV spectrum of the substance. After that, you can set the detector to the desired wavelength (ideally the one with the highest signal strength) and then do analyses at that specific wavelength.