[solarmeter®]

If he brings out his spectrometer, don't let him leave until he sums up the nm by nm irradiance as three bandwidths:

1. Total UV from 280-400nm (like a model 5.0 sees)
2. UVB from 280-320nm (like a model 6.0 sees)
3. Erythemally weighted UV from 280-400nm (like a model 7.0 sees and converts to MED/hr).

Then when you get your 6.0 and 7.0 meters you can compare.

For 3. above, the spectrometer scan might be from 250-400nm. If so that's OK because there is virtually no UVC from 250-280nm. The Ery weighted irradiance might be in W/m² or some similar units. That's OK too because I can convert that to MED/hr.

If the lamps are 5% UVB.... and the total UV is say 18.0 mW/cm²... then the UVB should be about 0.05 x 18.0 = 0.90 mW/cm². A "ratio" of UVB/UVA would be slightly higher "percent" but close.

The amount and percent of UVB is not as important as the MED/hr. Knowing that will help determine if the Te time to 4 MEDs is OK with the lamps/beds you have. Shortcut is Te = 240 / MED per hour.

And... needless to say... the hand held meter readings and the spectrometer readings should be taken at the same location. Usually center of bed pointing up near belly button position with canopy closed.

Readings from the bench are almost always less. That's OK too.