Author Topic: EEVblog #898 - LCD Contrast Experiments  (Read 19510 times)

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Offline EEVblogTopic starter

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EEVblog #898 - LCD Contrast Experiments
« on: July 07, 2016, 11:03:16 pm »
What is the difference between LCD viewing angle and bias angle?
How does adjusting the LCD bias voltage effect the display?
What is LCD Ghosting?
Also a demonstration of Photoelastic Birefringence in polycarbonate plastic display covers.
Dave investigates the Liquid Crystal Display viewing angle problem in the EEVblog BM235 Multimeter.

« Last Edit: July 08, 2016, 12:45:42 am by EEVblog »
 
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Offline imidis

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #1 on: July 08, 2016, 12:56:40 am »
Awesome! Thanks for trying it.   :)
Gone for good
 

Offline nidlaX

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #2 on: July 08, 2016, 03:40:37 am »
Very nice Dave! For your customers, will it void their warranties if they choose to change the bias resistor?

I'm tempted to do this for my Greenlee DM-510A, but I'm almost certain the warranty will be void if I do.
 

Offline GEuser

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #3 on: July 08, 2016, 04:18:19 am »
Good one Dave , i dunno where you find the time .

You forgot though to turn on the backlight at the end to see what happens .
Soon
 

Offline EEVblogTopic starter

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #4 on: July 08, 2016, 04:52:58 am »
You forgot though to turn on the backlight at the end to see what happens .

Yep, I forget a lot of things.
 

Offline EEVblogTopic starter

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #5 on: July 08, 2016, 04:53:41 am »
Very nice Dave! For your customers, will it void their warranties if they choose to change the bias resistor?

Not unless the mod demonstrably caused the fault.
 

Online Brumby

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #6 on: July 08, 2016, 05:07:33 am »
Good to know.

Then again, people who purchase a product like this are more likely to have the skills to make such a mod.  I know I could - but, at the moment, I have no plans to fix the backlight buzz nor contrast.  This might change if a situation arises where there is a clear benefit - but I'm not into mods for the sake of mods.
 

Offline EEVblogTopic starter

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #7 on: July 08, 2016, 05:09:47 am »
Good to know.
Then again, people who purchase a product like this are more likely to have the skills to make such a mod.  I know I could - but, at the moment, I have no plans to fix the backlight buzz nor contrast.  This might change if a situation arises where there is a clear benefit - but I'm not into mods for the sake of mods.

I won't bother modding my own lab units, doesn't cause an issue for me.
 

Offline TheDefpom

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #8 on: July 08, 2016, 05:21:48 am »
The polarizing effect is due to the crystallization of the plastic housing, polarizing filters are used to check for the internal stresses and melt flow properties of these kinds of plastics, if you look at the effect through the filter, you can actually see it shows where the injection moulded fill points where (the gates), but normally you would not see this at all unless you are looking through a polarized filter, such as sunglasses, etc.
« Last Edit: July 08, 2016, 05:34:21 am by TheDefpom »
Cheers Scott

Check out my Electronics Repair, Mailbag, or Review Videos at https://www.youtube.com/TheDefpom
 

Offline TheDefpom

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #9 on: July 08, 2016, 05:35:37 am »
I think I will have a look at my one and decide if I should replace that resistor or not.
Cheers Scott

Check out my Electronics Repair, Mailbag, or Review Videos at https://www.youtube.com/TheDefpom
 

Offline f4eru

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #10 on: July 08, 2016, 01:10:42 pm »
Wov !!

Dave made a demo of the Davecad V2.0 in this video, with animation features !
Innovation in the CAD field :)
I hope this V2.0 will be released soon :)
 
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Offline EEVblogTopic starter

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #11 on: July 08, 2016, 01:20:51 pm »
Dave made a demo of the Davecad V2.0 in this video, with animation features !
Innovation in the CAD field :)
I hope this V2.0 will be released soon :)

Big announcement video coming shortly, I've sold DaveCAD to a large CAD company who shall remain nameless right now. Will post it from my new private island.
 

Online nctnico

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #12 on: July 08, 2016, 02:23:13 pm »
Dave made a demo of the Davecad V2.0 in this video, with animation features !
Innovation in the CAD field :)
I hope this V2.0 will be released soon :)
Big announcement video coming shortly, I've sold DaveCAD to a large CAD company who shall remain nameless right now. Will post it from my new private island.
Let me guess: Staples?
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Macbeth

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #13 on: July 08, 2016, 02:44:58 pm »
I am in awe of the new DaveCAD transparent animation plugin. Patent it before Solidworks steal it for themselves!  :-+
 

Online Brumby

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #14 on: July 08, 2016, 03:33:09 pm »
Sorry I didn't comment earlier, but I, too, was impressed by the animation plugin!

Looks like it can handle multiple layers as well.  Impressive.
 

Offline Hootch

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #15 on: July 08, 2016, 03:44:02 pm »
Big announcement video coming shortly, I've sold DaveCAD to a large CAD company who shall remain nameless right now. Will post it from my new private island.
You just revealed it: 3M  :)
 

Offline rrinker

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #16 on: July 08, 2016, 06:16:29 pm »
Dave made a demo of the Davecad V2.0 in this video, with animation features !
Innovation in the CAD field :)
I hope this V2.0 will be released soon :)

Big announcement video coming shortly, I've sold DaveCAD to a large CAD company who shall remain nameless right now. Will post it from my new private island.

 Altium owned an ISLAND, too?

 

Offline Howardlong

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #17 on: July 10, 2016, 04:58:42 pm »
39k on my two units, 20k was an improvement, but 39k much better.
 

Offline BobC

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #18 on: July 10, 2016, 08:27:57 pm »
Trap for Young Players:  When purchasing a device for outdoor use, always take it outdoors and view it while wearing your polarized sunglasses!

Way too many displays need to be turned sideways to be legible when wearing polarized glasses. I haven't seen the problem in my recent multimeters, but it was present in some older ones.

The first Android phone I purchased, an LG L9, worked great outdoors at all orientations (I still need to figure out how they pulled that one off).  But I forgot to check my next phone, a Samsung Galaxy Avant, and it turned out to be viewable only in portrait orientation, which fortunately works fine for Google Maps, but not for any of my fitness tracking apps.  Arrgh!
 

Offline amyk

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #19 on: July 11, 2016, 01:44:24 am »
Trap for Young Players:  When purchasing a device for outdoor use, always take it outdoors and view it while wearing your polarized sunglasses!

Way too many displays need to be turned sideways to be legible when wearing polarized glasses. I haven't seen the problem in my recent multimeters, but it was present in some older ones.

The first Android phone I purchased, an LG L9, worked great outdoors at all orientations (I still need to figure out how they pulled that one off).  But I forgot to check my next phone, a Samsung Galaxy Avant, and it turned out to be viewable only in portrait orientation, which fortunately works fine for Google Maps, but not for any of my fitness tracking apps.  Arrgh!
That's because some of them use 45-degree polarisation while others are 0/90.

http://electronics.stackexchange.com/questions/28113/why-are-lcd-panels-polarized-at-45-degrees

And of course those using OLED will be visible at any angle.
 

Online Brumby

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #20 on: July 11, 2016, 03:10:55 am »
Trap for Young Players:  When purchasing a device for outdoor use, always take it outdoors and view it while wearing your polarized sunglasses!

Way too many displays need to be turned sideways to be legible when wearing polarized glasses. I haven't seen the problem in my recent multimeters, but it was present in some older ones.

Yes, the polarization experiment needs to be done before purchase.


An aside.... I remember walking down the street one day wearing my polarized sunnies when I spotted a woman walking in the opposite direction wearing hers.  The only trouble was, with her glasses one lens was clear and the other was black and a quick tilt of my head confirmed hers were polarizing.  I expect one of the lenses had been put in 90º out of whack - which was possible because they were perfectly circular.  I wonder if she ever had a glare problem with her left eye.......
 

Offline amyk

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #21 on: July 11, 2016, 10:23:34 am »
Trap for Young Players:  When purchasing a device for outdoor use, always take it outdoors and view it while wearing your polarized sunglasses!

Way too many displays need to be turned sideways to be legible when wearing polarized glasses. I haven't seen the problem in my recent multimeters, but it was present in some older ones.

Yes, the polarization experiment needs to be done before purchase.


An aside.... I remember walking down the street one day wearing my polarized sunnies when I spotted a woman walking in the opposite direction wearing hers.  The only trouble was, with her glasses one lens was clear and the other was black and a quick tilt of my head confirmed hers were polarizing.  I expect one of the lenses had been put in 90º out of whack - which was possible because they were perfectly circular.  I wonder if she ever had a glare problem with her left eye.......
She'd probably see the same thing and wonder why your glasses had the lenses wrong...
 

Offline LazyJack

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #22 on: July 11, 2016, 10:35:38 am »
Trap for Young Players:  When purchasing a device for outdoor use, always take it outdoors and view it while wearing your polarized sunglasses!

Way too many displays need to be turned sideways to be legible when wearing polarized glasses. I haven't seen the problem in my recent multimeters, but it was present in some older ones.

The first Android phone I purchased, an LG L9, worked great outdoors at all orientations (I still need to figure out how they pulled that one off).  But I forgot to check my next phone, a Samsung Galaxy Avant, and it turned out to be viewable only in portrait orientation, which fortunately works fine for Google Maps, but not for any of my fitness tracking apps.  Arrgh!

Yeah! Trap indeed. This is something a lot of marine instrument manufacturers still need to learn. On my boat, when wearing polarizing sunglasses (practically all the time, when it's not dark around) I need to constantly tilt my head back and forth to either see the depth sounder or the autopilot display.
But I've been to cars, where various displays, like radio and A/C did not have the same polarization, so one of them was always black in polar glasses.
 

Offline bktemp

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #23 on: July 11, 2016, 11:08:27 am »
And of course those using OLED will be visible at any angle.
For OLEDs itself this is true, but there are sometimes polarizers added to the display to reduce glare.
 

Online Brumby

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #24 on: July 11, 2016, 12:43:10 pm »
Trap for Young Players:  When purchasing a device for outdoor use, always take it outdoors and view it while wearing your polarized sunglasses!

Way too many displays need to be turned sideways to be legible when wearing polarized glasses. I haven't seen the problem in my recent multimeters, but it was present in some older ones.

Yes, the polarization experiment needs to be done before purchase.


An aside.... I remember walking down the street one day wearing my polarized sunnies when I spotted a woman walking in the opposite direction wearing hers.  The only trouble was, with her glasses one lens was clear and the other was black and a quick tilt of my head confirmed hers were polarizing.  I expect one of the lenses had been put in 90º out of whack - which was possible because they were perfectly circular.  I wonder if she ever had a glare problem with her left eye.......
She'd probably see the same thing and wonder why your glasses had the lenses wrong...

Not sure about that.  Her left eye would see my glasses as being black on both sides and her right would see them as clear.  With binocular vision, these two images would be overlaid in the brain and the problem would not be immediately obvious.

Her left eye, however, would not have been getting the protection of polarizing filtering in the normal plane.
 

Offline vince53

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #25 on: July 11, 2016, 02:36:10 pm »
Good work Dave,

I have noticed the contrast issue but have gotten around it by using the backlight all the time.  I'll get around to making the mod.

Thanks,
Vince
 

Offline Porto

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #26 on: July 11, 2016, 09:34:10 pm »
OLED, the only way to go!  :-+




 

Online Brumby

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #27 on: July 12, 2016, 02:48:53 am »
Great indoors.  They are 'challenged' in daylight.
 

Offline Fungus

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #28 on: July 12, 2016, 10:25:19 am »
OLED, the only way to go!  :-+

In a dark room, sure...

(...and if you don't mind changing the batteries every few days)
 

Offline Howardlong

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #29 on: July 14, 2016, 10:42:39 am »
(...and if you don't mind changing the batteries every few days)

Single biggest reason not to go for OLED!
 

Offline tungsten2k

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #30 on: January 10, 2017, 08:51:16 pm »
Great DaveCAD demonstration as always ! I remember enjoying this video when posted and am now revisiting due to investigation of similar problem I'm finding on nearly every LCD power control meter (e.g. Peacefair, etc) but having a tough time tracing it down. I want to stay away from led segment display due to light-sensitive environment these will be used in.

For those who don't have the EEVBlog or Bryman meter to review, any pointer on thought process one would use determine how to find the contrast bias angle resistor if Bryman hadn't provided it ?

Thanks for the video !
 

Offline denisber

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #31 on: April 30, 2019, 07:35:16 pm »
Hi,

I bought a DMM Yokogawa Ty720 and wanted to change the bias resistor too.

How do find the bias resistor?
Do they have some tips?

I haven't a schematic or service manual.


Thanks for any help!
 

Offline arturmariojr

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Re: EEVblog #898 - LCD Contrast Experiments
« Reply #32 on: September 21, 2022, 02:02:56 pm »
Hi, Denis

Could you improve the visibility of your Yokogawa meter?

Best regards
Artur
 


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