This is the one I favour =
https://www.solarmeter.com/model62.html, it gives a direct reading in microW UVB / sq.cm so I know when my sources are no longer emitting sufficient UVB . This was the first one I bought and I really find it useful and I use this one very regularly , as the reading gives me the best indication of how much VitD3 my pet skinks and dragon will be producing naturally.
I also have
https://www.solarmeter.com/model42.html (recent purchase) so I can now also check the UVA , I used this less than the model62 , and I also bought a
https://www.solarmeter.com/model65.html (this was recommended by some knowledgeable folks at the BeardedDragon board - but I only plan to use it infrequently.
I set up my meters the same distance from the UV source as the basking spot.
Now I speak as a engineer and physicist ( I am both ) :
Very important to get the meter directly under and properly aligned as the microW UV flux reading is very sensitive to distance and the view factor of the sensor
for those with a math or physics or engineering bent see this diagram and relevant model

, and very important to standardize your measurement technique to be sure you are getting accurate readings that are reproduceable. UV meters are expensive and unless you take care to measure properly you are wasting your money buying one (or more).
This is a good read and will help you get a handle on how to use your meter :
http://www.uvguide.co.uk/usinguvmeter.htm and
http://www.uvguide.co.uk/usinguvmeter.htmI find it convenient hang a plumb-bob under the centre of the bottom face of the source and line the axis of the meter up with plumb-bob's string (gives me the "Normal" and the exactly were the axis should be (takes care of the view effect effect) and distance is measured.