5 luxmeters compared (april 2018)

[moderator007]

I have calibrated mine and used off and on for months and go to check calibration again and its still spot on.
It could be meter specific though, I would try the battery first like Muto suggested.
Temperature could also change the reading a little, I know a few degrees cooler battery can decrease current capabilties.
Li-ions perform better when warmer.

[ChibiM]

would be interesting to know for sure, if they can drift off so quickly.

[djozz]

I have not seen luxmeters noticably shift myself,

I have my Mobilux meter that was 3.4% off two years ago when I compared it next to one that was calibrated that same year. It had not been calibrated for 8 years at that point. Officially they need re-calibrating every year but it feels not needed.

Before that I used a Tondaj meter for years, and my reference flashlight measured the same within 1% for years.

Maybe you see some yellowing of the inner surface of your sphere over time? But that is expected from the influence of light, and generally the inside of a sphere is dark.

[EasyB]

Thanks, I’ll try to see if the battery or temperature changes the reading.

[djozz]

@EasyB

Thanks, I’ll try to see if the battery or temperature changes the reading.

I remembered that I did something with temperature before and behold I found it within 5 minutes which is lucky because it is buried in a thread from 2014:

Luxmeters: thoughts, findings, comparison

Because it was a quite easy test, I did a rough test on temperature effects on the reading of the Tondaj and Mobilux luxmeters. Method: I put the sensors (not the body) in the fridge, next to each other together with a thermometer. After 3.5 hours (the thermometer read 12degC) I took them out, attached them to a cupboard and measured the lux of the hotspot of my k10 constant output reference light at an arbritrary distance (1.2 meter or so) clamped in a stand. Then I took the readings of the met…

[EasyB]

Thanks, that’s good info djozz.

I tested the voltage dependence of my meter. The 9V battery was at 8.8V OC (8.4V under load with the meter on). To test the voltage dependence I connected my power supply to the meter input and measured a light while varying the voltage from 7V to 9.2V and there was no change (less than 3%). So, I’m not sure what caused my issue.