Author Topic: Multimeter Vacuum Fluorescent Displays & Dot Matrix Aging problems explained  (Read 296 times)

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Online Kiriakos GR

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Vacuum Fluorescent Displays & Dot Matrix - Exploration of percentage of Damage due aging

Intro:

Dear ITTSB Blog visitors after reading this Blog entry there is a big chance to reevaluate what your eyes are looking at when you are up to a used benchtop multimeter on eBay end or else ware. 

My personal story is that I shopped a used benchtop multimeter this having VFD Dot matrix, product pictures which I did reviewed they was good.
My decision about exact product model this was made by primarily thinking which one is best for my applications’, rich features’ and tightest accuracy at 6 ½ digits.
 
After product arrival I was able to verify that my benchtop DMM this is six years old, I did notice slight burning (soft shadows) over most frequently used VFD chips.
Now and after performing deepest research regarding Vacuum Fluorescent Displays appearance when they are photographed by a digital camera, I consider my findings as extraordinary and unique as information.   :)
 
 
Now let’s talk about digital cameras and of how neutral they are resolving true colors.
Vacuum fluorescent displays they are active chemistry in cooperation with electricity , VFD chip brightness it is radiation of specific color frequency, the addition of a LENS filter it can further influence actual color.
I am a hobbyist photographer for 19 years up to date, my trusty digital Olympus C2100 it was famous for it neutral performance in entire color spectrum by a small exception in purple, mostly due it Ultra-zoom 10X lens design, this is prone to chromatic aberration.
( Chromatic aberration this appears as purple line between two high in contrast objects’ under specific lighting and angle conditions. )
 
Now specifically this Tektronix DMM4050 at stock photos, it is demonstrated as this having a blue tint, and also as such it appear in the picture of my seller which he use a Samsung Galaxy S7 SM-G930F to take the pictures.       
My own eyes and my camera, both recorded this as green color and as soon VFD Lens was removed from face-plate, this VFD delivered 70% brighter digits in vivid green color.   


Vacuum fluorescent displays evaluation.
By everything I know today, I consider as almost impossible for some one to correctly evaluate aging of VFD display due digitally constructed pictures.
At benchtop DMM with basic type VFD tubes and a few segments, it is somewhat easier to define which segments deteriorated more than the others.
Even so there is no way determining differences in the rate of percentage. 
 
We, working in electronics repairs for a life time, we knew that VFD damage this is unavoidable and that only one new glass this will solve the problem.
From the other hand, if a used VFD this has still some life in it, and has only 40% degradation from a new, this is still usable but not for more than four years ahead.

VFD Dot matrix evaluation
Here I will suggest having first a good look at my pictures below and then return to read the rest of my text. 

In order to properly analyze Dot-Matrix degradation I was have to isolate a single photographed frame this be much faster than VFD refresh rate, therefore much less activity of chips was recorded on the picture, but we can see and focus better on the details. 

I think that I did succeed recording three main categories of chips health status.
a) Chips not frequently used were naturally most vivid ones (the ones activating in sub menus etc).
b) Chips frequently used these staying on all times.  These chips demonstrated a bit of less damage than the next category.
c)  Chips frequently used and frequently updated (high count of operations at getting on or off). These found to be the chips with highest deterioration regarding brightness and contrast.
 
Naturally a most careful evaluation of my pictures, this clearly demonstrates that its dot and it tiny filament, this could have quite different degree of deterioration from the next (256x64= almost 16384 dots).
 
Generally speaking I am now convinced that specific VFD this lost a total of 25% of brightness from a new at lowest brightness setting.
But this is not important, because over all it seems that TEK made some sort of wrong decision so to differentiate aesthetics of this Fluke 8846A, by making a wrong choice regarding LENS absorption degree (light filtering) which this removes significant amount of brightness, this now causing digits to look dim and dark when VFD this it does deliver a decent amount of light.
 

In conclusion
A semi-pro digital camera this is optimized to capture best image brightness by compensating Shutter-speed, therefore it is impossible to capture Dot matrix aging damage, and therefore all pictures of used benchtop DMM VFD they can be very illusive.

Another scam that a seller can do, this is compensating his digital camera settings.
Most tricky setting this is not using ISO-100 (film equivalent standard) but higher than that which makes everything looking brighter than what it is.

Because I do consider my perfectly working benchtop multimeter as a keeper, mostly for sentimental reasons I am planning to replace this used VFD glass by a new, so and we to have a fresh start within 2019.
Specific VFD Dot matrix glass this is made in Japan by Noritake Itron, still in production and available stock can be found in retail market.
Noritake Itron this has three branches within European Union.

 
Vacuum Fluorescent Displays technology this counts on high manufacturing standards’ for a long product life cycle, I did read several complains of Chinese users regarding domestic production of spare VFD for 34401A, degradation rate of made in China VFD this is much higher these days.
Noritake Itron VFD controller this includes three levels of brightness adjustment, you may use the lowest and preserve the life of your VFD Dot matrix for many more years.

At ITTSB Blog I do blogging all these years by presenting the naked truth, in the sector of used benchtop 90% of available models they are EOL with out spare parts.

Feel free to avoid sellers with out active business (people selling goods from their home). 

Always consider as obligation to your self about sending your freshly purchased used multimeter for a fresh (adjustment calibration) at a certified lab.
If it does pass from this last test too? Only then this worth to be described as good to go tool, for several years ahead.

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Offline overvolt

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Specific VFD Dot matrix glass this is made in Japan by Noritake Itron, still in production and available stock can be found in retail market.

This is what I am going to keep as Good News  :)

Such VFD Dot matrix glass this can be found and at some Yokogawa source-meter SMU.

 

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