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Written by Kiriakos A. Triantafillou, Industrial maintenance electrician, Hellas.

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Burn in of OLED's is a known problem

12 August  2012

OLED's and industrial electricians are two different worlds, but from the moment that Agilent choose to use OLED's in multimeter's, this change it did trigger my curiosity so to discover even more info about them.


If you do a web search about the name Ching Tang, you will discover the man who haves been credited for the discovery of OLED's.

While LCD displays still dominate the commercial market, the goal is those OLED's to become a more widely adopted technology.

From what I have read, the most important key points are that is cheap to build and very lightweight.     


About LCD displays I will make a list of the more known problems of them.

a) Fading in long term.

b) Heavy bleeding and death after a strong impact.

c) At very low temperatures some of them are unable to operate properly.

d) Finding an LCD display as replacement part, most of the times are impossible.


From the other hand, LCD displays is a true winning technology even today, as they are readable under any natural light condition.

By the adoption of LED back light, the LCD screens got the advantage to dominate even at the low light conditions.


What about OLED's?

Do they have their own dark secrets?


My first Google search on the subject did not bring anything as easy answer,

What I did found was complicate to understand scientific reports which they did not manage to scare me away.

By examining better the long text I did find what I was looking for.


The major factors which can cause damage to OLED's are:

1) Oxygen

2) Water (moisture)

3) leakage current


By the first look it seems that all those three factors have nothing to do with the end user, and that everything have to do with the quality of the manufacturing process it self.  


What happened in my case was that I started this in-depth search due my personal findings about Burn in traces, which I have noticed on the OLED display of the Agilent U1273A after one stress test for 120 Hours.

The test condition was to have the meter to operate at the Min/Max mode by measuring 220V Mains, the test was about finding the sum of operating hours with different sets of NiMH batteries.

At the end of those tests, I did use the display Test function that Agilent added on it, which powers up simultaneously the entire display surface, and I did noticed some soft traces which was have the shape of the digits.

Some were easy to see as they were produced by the digits which were remaining unchanged.

For example:

1) The first number of the 220V

2) The indications in the bar graph


By those findings I started immediately to look for more info about the burn in and OLED's, but instead I found the above information’s and not even one word about burn in.  


The next step was to come in direct communication with a manufacturer of those super yellow OLED's, so to find even more answers.

Thanks to Kopin Corporation and their Director of Marketing Mr. Alan Richard, I got the answer that I was looking for.


“Burn in of OLED's is a known problem.  It has gotten better over the years but still remains to some extent.

This can also be true for conventional LED's


I would say some burn in is to be expected with OLED's


Alan“



By putting together all the above pieces of the puzzle I think that now I have the complete picture.

But let’s see this picture in parts for a better understanding.


1) LCD VS OLED's about mechanical robustness’

The OLED's are made from flexible material and not glass, and so they do win hands down about be prone to damage due impact.


2) OLED's biggest enemies?

Oxygen / water / leakage current, all three of those factors are related with the manufacturing process.  


3) OLED's life cycle

The super yellow OLED haves the highest life cycle in comparison with OLED's in other colors, the estimation is about 100 thousands hours, which sound good enough.


4) OLED's functionality VS operating temperature.  

It looks that this technology offers a major advantage if the user is not human.

Personally I do not care if they can operate at minus 40C, for me it is impossible to stand next to it and read it at that temperature.  

Such extreme specifications usually become marketing hypes, which does not have real value for the average user.

Even so this information translates in to a simpler meaning, which is that OLED's are a good solution for very cold climates too.


5) OLED's Burn in

It is there and it is happening, in my testing I have use the dimmest brightness setting, but even so the burn in it did shown up.

It is not a sign of showing any true wear, but it did worry me as thought, mostly because I was not having the awareness that you are having now by reading this article.


What looks as truly weird is the fact that those “soft” burn in, looks just a bit brighter than the OLED which are not used that frequently.


About the U1273A OLED display it self, as long there is behind it one brand name like Agilent, I do not worry that much.

But I would feel much better by seeing it listed as spare part in their website.

#

Notes:

Any dark points in the screen are common external dust.

This picture was the hardest to capture since 2000 that I started as hobbyist photographer.

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