Extech UV505 Pocket UV AB Lichtmeter

I love it. Very expensive though.

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This meter does work. Although the strength of the reading appears to vary depending on the angle at which you point the detector at the light source a lot. I'm guessing this is because this uses some sort of colored filter as part of the design. Varying the angle of a filter can shift the frequency/band of light which comes into the filter, so you have to move the meter around to get an idea of how strong the uv can be from its source.It is important to note that this is not a UV index meter and cannot be equated to one as a UV index meter appears to use a weight scale formula based on certain frequencies in the UV spectrum. I'm not sure how this meter gathers light, but since it does appear to use a colored filter, I'm guessing it is probably not linear across the UV-AB band. If you've ever seen what kind of light/frequencies a colored filtered can let in, you'll know that it is not linear, but appears to go up and down letting in certain frequencies of light while blocking others. But then again, this is just a guess as I don't know the properties of the filter they use.Technically the UV-AB band goes all the way up to 400Nm, and this meter goes goes to 390Nm.. so it does not cover all the UV-A band. Although the UV-A band in that region is not as harmful to the skin as the other frequencies, so probably is not as important.It took a while to test this as we've been cloudy/rainy for a long while, but I did test it on some internal lights as well as my windows that filter out heat (gila window film), and it does work at showing relatively strength of UV light. Raw sunlight seem to hover around close to 1000 uW/cm2 or less. Where the gila window film appeared to only show numbers in the single digits or maybe close to 10 uW/cm2. Oddly enough, ordinary windows without any film blocked around 50-66% of uv light.As far as internal lights were concerned, most of my fluorescent lights gave negligible uv light.. again around 10uW/cm2 or sometimes less. while a UV led flashlight put out around 20 times more uv light... but the numbers appeared to jump around alot for some reason.There are other meters I've found that look just like this meter, but in different colors. Some of them cost a little bit less. But I don't know if the internal components are the same.For the price it is a good meter. If you want something more precise or with better range (for example, something that detects UV-C light as well), then you'll have to get another meter, or something more expensive.I did have a minor quibble with the unit button. It seems like the mW/cm2 tends to round things a bit up compared to the UW/cm2. Maybe this is done for safety purposes, I don' t know.

I'll start off saying that sometimes I can be, er, unobservant. I tend to not read instructions at first. Just dive in. The battery door is held in place with a locking mechanism that requires a button press to release. I did not notice the button and could not slide the door off. I finally pried it open with a screwdriver. *Then* I noticed the button. Nothing was damaged except my pride, attesting to the ruggedness of the door latch. WHY it needs a lock, I have no idea.I have a couple of UV-A/B meters, including one where the sensor is separate and connected by a cable. Which design is better for you really depends on where you're using the meter, but is something to consider. If the light reading is in a more cramped or hard to reach area, you can extend just the sensor and have the display easily accessible. But you trade off size and durability (I've had the cables go bad after time.) If you perform a lot of UV-A/B measurements, eventually you'll probably wind up with both styles - compact all-in-one units like this Extech UV505, and one with a separate sensor.The all-in-one is my preferred style because I can stick it in a pocket, small tool bag pouch (I found that the cell phone pocket works well). The Extech UV505 includes a decent holster/pouch with top flap and belt loop. You can hang it from a tool bag shoulder strap, belt, etc. or just toss it in a toolbox/bag.The screen is easy to read and slightly below the face of the unit, so if you rest it face down on a surface you won't scratch it. There's a sensor cover that protects the sensor and blocks light to make zero-ing out the meter quick and easy. Overall build quality is good, but it is all plastic with no bumpers - a drop from a few feet onto concrete could be a problem. There's also a 1/4-20 tripod thread on the back. 2 AAA batteries are also included (they're in the bottom of the holster!) There's a loop for a lanyard, but no lanyard is included.I don't have a lab to test accuracy, but it reads the same as my other two meters.