I made a second integrating sphere. I made it because my first sphere (thread about my first sphere here) had some properties and uncertainties that I thought needed improving. The major improvement will be that it makes use of the high quality (DIN 5032-7) class A Mobilux luxmeter, that is very accurate, very well V_lambda-corrected for all light colours, and has a very good range, from 0.01 lux to 200,000 lux. This second sphere is huge (outer size 54x54x54cm, inner diameter 46cm) compared to the first one and I'm not sure where to store it :-( . It is fully functional now apart from the coating on the inside (that will be a four layer 60%/40% BaSO4/latex paint mixture): the inner surface is still bare styrofoam, although sanded carefully with 1000 grit sandpaper to remove most of the direct reflectiveness.
I post about it now, before finishing it, to stimulate myself to carry on with it.
It has three ports, an entrance port on top with 80mm diameter (I made an insert for it, reducing it to a 30mm port), a side port for the luxmeter sensor, and an extra 30mm side port that can be used either as an entrance port (for the conversion factor adjustment light) or as a measuring port. (as a consequence of the 3 ports it has 3 baffles on the inside between the ports, I will add some pictures of that later).
I still have to characterise this sphere. One of the things is that I want to measure carefully is what the influence will be of the coating: on the intergrating properties and on the wavelength response. I made a number of constant output light sources for that: cool white, neutral white, warm white, red, green, blue, basically low output small flashlights that run on one or two 7135 chips.
Below my test plans, just to give an idea; they are mostly notes to myself, I did not write it down with the intention that it is all clearly explained
More later!
EDITS : some progress in post #16 : a conversion factor correction light is added.
progress in post #38 : six reference flashlights were measured in the still uncoated sphere
some details of the sphere in post #40.
start of coating in post #42
coating finshed and tested in post #45
an extra accurate test on the integrating properties in post #64