Dialux showing lower value of lux than expected.

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Joined: Thu Apr 26, 2018 11:13 am

Dialux showing lower value of lux than expected.

Post by PeterRichard » Sun Sep 23, 2018 8:50 am

I realise another user has posted what looks like a similar query,

".ies shows lower lux value then manufacturer provides"

But I have been very careful - and there is no "real world scenario" to worry about. It's all about Dialux.

I downloaded the data from an .IES file into Excel.

I computed the total lumens for the lamp and that total agreed with the manufactures claim, showing that my calculations were correct. (I multiplied the intensity by the area of the rings and totalled the whole lot).

Looking in the .IES file, One can see that the intensity perpendicular to the luminaire, where it is maximum, is 72,530 cd. So at 10m from the luminaire one would expect the illuminace to be 725 lux.

I opened Dialux 4.13 and I checked to ensure that the Maintenance Factor = Light Loss Factor = 1.0

I installed the luminaire into Dialux, locating it at 10m above a tennis court with absolutely nothing else around.

Dialux told me the illuminance immediately below the luminaire, where it is a maximum, would be 538 lux.

How do you account for this discrepancy. It is big one.

Posts: 1519
Joined: Wed Mar 07, 2012 3:07 pm

Re: Dialux showing lower value of lux than expected.

Post by Csuleiman » Tue Sep 25, 2018 8:05 am

Dear PeterRichard,

Thank you very much for providing us with your project file and the PDF document.

The problem described is actually not a problem in DIALux. If you change the light loss factor in the settings of DIALux, the change will always affect a newly created project. In the existing project, the adjustment in the settings has no effect. However, you can easily change the light loss factor in the project itself, so that it also has an influence on the calculation. Please have a look at the following screenshots.

Screenshot1.JPG (97.02 KiB) Viewed 1002 times
Screenshot2.JPG (143.25 KiB) Viewed 1002 times

Best regards,
DIAL Support Team


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