I had one of these in the prepress dept...

http://www.ebay.com/itm/UVP-BLAK-RAY...item4aaf9c8310

The way I used it was to turn on the lights in the photopolymer platemaker, a unit with tightly spaced rows of fluorescent bulbs, maybe a dozen 48 inch bulbs. They weren't blacklight, because they put out plenty of regular light, but they were special bulbs that put out a lot of UV. I'd touch the four bumps of the sensor against each bulb and run from one end to the other and watch the needle. If any bulb was dying, you'd never know by the white light because the bulb would look plenty bright, but the needle would take quite a dive.

So your meter, you can use it to make sure your light is performing as it was the last time you used it. Or you can judge the UV of daylight. Or you can go shopping for UV light sources and pick the source that gets you the highest readings.

So even though I always used material with a consistent response to light, I never "calibrated" any device in the shop to a particular setting based on a published speed of a plate or film. I always burned a Stouffer wedge with each plate - and adjusted exposure based on the results on the test strip. Nobody in the shop ever dared make even one plate or film without a step wedge on it.