Did you try changing the batteries in your meter?
I always calibrate befoore taking measurements. Not with Lisun bulb but with three calibration lights to make sure everything is in order. There is usually some variation (a percent or two maybe) between sessions but as long as the correction factor between the lights doesn’t differ more than half a percent, everything is go. So there hasn’t been any lomg term drift for me and I also use an S2+ as one of the cal lights.
Dust is an issue I have, I have to clean my sphere every week or so to keep readings the same.
I have a SWM D40A (I measure the highest regulated setting) that I check my sphere with, and it reads between 10.95 and 10.85 (before multiplier, it is around 550 djozz-lumen) for years on end now. So it should be possible to stay consistent with home-made light measuring contraptions.
I do remove dust and grit inside the sphere every now and then with a vacuum cleaner, although some visible dust does not alter readings significantly.
Maukka… that set-up is DOPE!
lol what do you do for work? I’m very curious what professions utilize integrating spheres and the rest of your equipment.
I also one day want to build a lumen tube… maybe a sphere… lol I’m pretty ambitious but those both being a long time away I just wanted to say it’s very cool you taking the time to provide proper calibration equipment to the forum, 
He spent thousands of dollars for this equipment, not as part of his job, but just as a hobby. Cool, huh?
ARRRRRRRRRRRR!!! I didn’t catch that until just now…… 5.XX volts in the battery left. 
The readings were not only off they were scattered. They were all high, but not even by the same percentage. That pretty much took care of it. Now to go back and make updates all over the internet.
<3
Hey guys, am I calibrating my sphere based on the MID mode from (low,mid,high) on the driver?
Yeah, Mid.
Thx, was sanding down my sphere and wanted to make sure before I taken too much material off.
I use the BLF348 for the low calibration and the mid mode of the S2+ for the mid range calibration but honestly if the mid mode on the S2+ is good the 348 has always matched up as well.
This gives me a chuckle! My first measuring space was the small bathroom in the house and now, and you may have seen it, but I have an integrating 68 quart Coleman cooler. So, I call them 'Coleman Lumens'.
TK, Absorbing yours and others comments about determining OTF output with a DMM and improving my technique on that front, I've realized that OTF lumens are the real test... and has saved me $40.00 for a new clamp meter. This discussion on throwier v's flooder lights really helps me, going forward, on how to calibrate the readings (so far, 25 lights & combinations) with my Budget Lumen Measuring Rig.
Maukka, Your work is very much appreciated. Thank you!
Hi Maukka,
Are you still selling calibrated lights? I am from the Philiipines and I want to use your calibrated lights for my lumentube.
Yes, I’ll send you a message.
Thank you very much!
Hi Maukka!
I would like to buy a light for my 150mm tube built by ZozzV6 (he used your lights set to set the filters)
I think one light with 2 known steps should be enough to double check the tube now and then?
One brightness setting per calibration light is plenty, since something catastrophic would have to happen to the lux meter for it not to be linear. Using two lights is recommended as small differences in beam profile, CCT and CRI helps checking for multiple possible issues and also reveals problems in integration and or meter if the initial values start to drift.
It’s normal for the lumens for both lights to be not exactly spot on as reported because of lux meter sensitivity inaccuracies, but if the difference between them changes suddenly, that’s a good indicator of something gone wrong with the setup.
I have 5 BLF348s left, but only one low CRI S2+. None of them have been measured at the moment.
I have 3 high CRI S2+ with SST20 4000K coming in shortly, but if you want to check your meter and sphere against a low and high CRI lights, I can have the S2+ and BLF348 bundled for you tomorrow. The SST20 versions will be available next week at the earliest.
I will configure these new SST20 S2+ for 100% mode only. They have 3x7135 chips and are quite idiotproof in this configuration.
idiotproof sounds like made for me ;)
i just want a easy (and non expensive) way to check my equipment
whatever you suggest - i will "maukka said so..." use against any doubts :D
Hi everyone,
I bought the calibration lights from Maukka (great service, and super quick delivery!) but after “calibrating” my lumen tube and getting the multipliers for the two calibration lights, all my other lights are reading quite low.
Here’s what my tube looks like. I’m not sure if it’s just a bad design and if I need to tweak it or start again in a different shape, or…?
I make sure to cover the glass panel with a black cloth when a light is sitting on it. I’ve tried putting a piece of paper under the glass to act as a diffuser but it doesn’t really change the accuracy of the results, it just lowers the lux reading. I can in fact get the lux : lumen ratio almost 1:1 with my calibration lights this way, but it still makes all my other lights read either far too high or far too low.
Am I missing something really obvious?
