Sorry if my last post was a little gruff, but I was pretty upset at the time. OK, so here's the deal. After testing the meter against known Finnex values on two different lights, I'm seeing the values are still 2 to 3 times as high as Finnex's published data. I purchased another DIY meter from a different builder here on TPT. Testing against the Finnex values the new meter was accurate to +/- 5%, I'd call that good enough. Now that I had something to calibrate to I decided to "fiddle with the pot" to my surprise to pot was already turned down as low as it could go. I'll give you credit in that it was reading 55 at 6" from the CFL, but as soon as you use a different source, the numbers begin to rapidly increase from reality. I called around and found a hydroponics shop that had an Apogee MQ200 that they said I could use in the store. We ran all three meters together with MH, T5HO, and CFL sources. Again your meter only gave decent readings with the CFL, but with the other lighting sources and your meter was again reading two to three times higher than both the "other DIY" meter and the Apogee. I guess I can't really be too upset if you intended this meter to be specifically used on that particular CFL configuration. I know now for a fact after my last posting that I am not the only one having this issue with the meter. I would like to encourage others who have the meter to compare it with a legit PAR meter and see what the results are. The thing that kinda burned me was that since the pot was turned all the way down, you either did not test the unit, or you tried to trim it down so that the high readings would not be as glaringly obvious. Again, I apologize for the derail and my prior rudeness. If you would please PM me your address I will send the meter back.