Main disadvantage to a VFD is power consumption is several watts.FWIW, I only see this as important for portable gear. ;D
Used in message critical applicationsAnd try to beat this:
VFDs are used in message critical applications since individual dot or segment failure does not occur during normal service life.
This is particularly important in cash registers, measuring instruments and medical equipment.
Rugged in any environment without compromise.
VFD displays are capable of operating from -40C to +85C in high humidity conditions due to the materials and construction used.
Typical module MTBF is 1,000,000 hours due to the integration of the display drivers in the sealed glass VFD envelope.
And try to beat this:QuoteRugged in any environment without compromise.
VFD displays are capable of operating from -40C to +85C in high humidity conditions due to the materials and construction used.
Typical module MTBF is 1,000,000 hours due to the integration of the display drivers in the sealed glass VFD envelope.
114 years of Mean Time Between Failure? One can only wonder how they tested that. :)Reliability engineering, you can change some parameters and multiply the lifetime by the corresponding factors.
Here is interesting comparison table. Interesting that none mentions the TFEL technology, it have been also around for decades by now. https://beneq.com/en/displays/technologyOLED is competing but not for large size displays.
OLED is limited by brightness. AMOLED is better in this regard, but it still can't compete VFD.
VFD doesn't require conductive film to pass current to pixels, while OLED does. That means, the thicker the conductor layer, the more light it absorbs. However, if the layer is too thin, it doesn't pass too much current. There's a balance between them.
Also, OLED pixels operate at very low voltage, from 5V~15V, while VFD operates at 50V+, so for the same current, even if VFD needs the same conductive film layer, it can be much thinner and hence allowing much more light to pass.
Another problem is burn in. OLEDs also suffer from burn in, and if you drive it to the same power level of VFD, it burns in faster. Don't believe me? Go to best buy and take a look at some demo units of OLED phones.
This is normally not an issue since nobody uses their phones 12 hours per day, but for a piece of equipment, 12*7 or even 24*7 operation is common, and despite VFD ages and burns in, it's not bad compared with other technologies.
Maybe LCDs are better, but some IGZO LCDs (particularly, Microsoft Surface Pro 3) also suffer from severe burn in, so who knows. At least VFD is verified by industry for decades to be reliable.
It's like asking "Why a Range Rover SUV instead of a Toyota?"
Well, the Toyota is cheaper and more readily available, and it performs a similar basic function. But you can't depend on the Toyota to cross the same terrain, or to look as good while doing it, as the Range Rover. And that essentially echos all the sentiments expressed above.
And, since a VFD is a vacuum tube, they laugh at 90C! So, the life at 90C is the same as 20C. Apply the Boltzman curve, and you extrapolate a crazy MTBF. Yes, it is all a house of mirrors.114 years of Mean Time Between Failure? One can only wonder how they tested that. :)Reliability engineering, you can change some parameters and multiply the lifetime by the corresponding factors.
I don't know these statistical factors but lets say 100 of your electronic devices are put in a hot chamber of 90 degrees C and a humidity of 80% and the average of those devices last 10 months than with those statistical factors you could for instance multiply that by 50 and get an average expected lifetime of 41 years.
I don't think you quite grasp MTBF. It is not the average time for a single example of the device to fail. It tells you the average aggregated failure rate. So for your military radio with 100 year MTBF ... if they have for example 5000 of those radios in service, they will expect 5000units/100yr = 50 units/year fail, or about one failure per week failure rate out of the 5000 unit fleet. Generally, the rate is higher initially (infant mortality), tapers off to a lower steady rate, then climbs again near end of design lifetime, at which point you retire the lot, working or not (unless you want to expose your organization to the climbing failure rate). MTBF tells you the average rate of failures in a fleet of units between deployment and retirement, not the individual unit lifetime.And, since a VFD is a vacuum tube, they laugh at 90C! So, the life at 90C is the same as 20C. Apply the Boltzman curve, and you extrapolate a crazy MTBF. Yes, it is all a house of mirrors.114 years of Mean Time Between Failure? One can only wonder how they tested that. :)Reliability engineering, you can change some parameters and multiply the lifetime by the corresponding factors.
I don't know these statistical factors but lets say 100 of your electronic devices are put in a hot chamber of 90 degrees C and a humidity of 80% and the average of those devices last 10 months than with those statistical factors you could for instance multiply that by 50 and get an average expected lifetime of 41 years.
My favorite was the tantalum capacitor debacle. A well-known failure mechanism of tantalum capacitors is you run a device for a while, put it on a shelf for 2-5 years, turn it back on and several tantalum caps fail shorted when the DC power abruptly turns on. So, the US military specified tantalum caps for a wide range of gear, severe accelerated life testing showed great results, and then they built thousands of radios, radars, computers and such, and after a good test run at the factory, it all went on the shelf at the supply depot! Perfect recipe for this problem.
But, if you know the system for doing this MTBF estimation, it is so TOTALLY bogus. You count the number of each type of component, look up the MTBF for each type, and then combine it all with a formula, and there's your MTBF number! This is all done with a spreadsheet, not with any sort of testing of the complete device. It totally ignores such factors as the load a component carries, the duty cycle of the load, thermal cycling, ESD at external connections, physical handling, and many other issues. But, this bogus system produces totally WHACKY numbers like a whole military field radio with 100+ years MTBF. Oh, RIGHT!
...
Jon
May be a bit off topic but I have recently encountered an electro fluorescent EL display for the first time. I originally thought it was just a LCD display with a EL backlight but is actually quite different. The one I have is faulty with I think a bad driver IC and i will be doing a repair on this in the future. Never one to avoid a bit of shameless self promotion see Part 2 here.https://youtu.be/jKxbjdt8dT8 (https://youtu.be/jKxbjdt8dT8)
This is being used in HP telecoms analyser from what I can tell back in the day they were popular in high end equipment but very expensive. You probably won't want to watch the whole video so start 12 minutes in. Actually if you are interested Part 1 does show more of the display in action as I play with the equipment and as always have no idea what I'm doing.
My best regards Chris.