Uses for vacuum tubes in 2023 - Page 1
Forum section: electronics / projects

author: S57UUU
author_rank: Regular Contributor
timestamp: October 30, 2023, 05:20:11 am
content: To avoid flame wars, please let's not discuss audio here.For a long time after commercial availability of transistors, vacuum tubes still remained strong in some applications, like high impedance input amplifiers, RF power, etc. CRTs reigned supreme, with no signs they were an endangered species, until suddenly driven to extinction by flat displays. (I am an old fart, so it seemed sudden to me.) So, where do tubes remain viable today? Some applications I can think of:1. Megawatt microwave power for particle accelerators and fusion reactors. (In fact, a particle accelerator itself is a vacuum tube, very literally!) Microwave transistor must be small, so a single device cannot provide very high power. Because of their small thermal mass, their peak to average power ratio is also small, like <2:1 compared to 1000:1 for tubes. You can combine a number of them. But if you need the power at a single point (connector), you need a combining network, which is lossy. More transistors mean a more complex combining network with higher losses, so there are diminishing returns, as the number of transistors increases.Where you can combine the power "in the air", like AESA radar, there is no combining network and no related losses. So most radars currently produced are solid state. In weather radars, magnetrons still often tend to be used, for economic reasons.2. Microwave ovens and industrial microwave heating. Mass produced oven magnetrons are so cheap, that transistors have a very hard time competing. Semiconductor manufacturers have been promising (and producing?) oven transistors for at least a decade, but I have yet to see a solid state oven in an department store.3. Large area photodetectors. Small solid state photodetectors can be faster and at least as sensitive as photomultipliers (fiber optics). They can be also made large (solar cells), but these are very slow due to their high capacitance. If you need to detect fast events over a large area, like in neutrino detectors, photomultipliers are still your friend. The biggest ones are decimeter sized, look like old CRTs.So, can you think of some other areas, where tubes still rein?

author: S57UUU
author_rank: Regular Contributor
timestamp: October 30, 2023, 05:34:20 am
content: One more application I remembered:4. TWTs are still sometimes used on spacecraft, for reliability reasons. It's funny that a tube could be more reliable than a transistor, but I guess it is the radiation environment of outer space that can kill the trasistors more easily than tubes. BTW, amplifiers in transoceanic cables were also biult with tubes for some time after transistors were available, for reliability reasons!

author: PCB.Wiz
author_rank: Super Contributor
timestamp: October 30, 2023, 05:57:45 am
content: There is also thishttps://www.eevblog.com/forum/projects/is-there-any-logical-reason-to-use-a-tube-as-the-oscillator-in-a-dac/

author: Kleinstein
author_rank: Super Contributor
timestamp: October 30, 2023, 09:11:54 am
content: Tubes are still a good choice if one can not tolerate a short as a failure mode. Even if transistors are more reliable they tend to fail with a short, while tubes often fail open (loss off cathode emission). So for some linear regulated higher voltage supplies a tube can still be a reasonable choice. I have seen and used a linear regulated 10 kV 1 A power supply - though in the use case a SMPS would be OK now.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 30, 2023, 09:59:03 am
content: Quote from: S57UUU on October 30, 2023, 05:20:11 amWhy not? It is, indeed, an item of current production. The engineering merits might be... dubious let's say, but a good engineer knows the totality of a product is more than just the engineering behind it.QuotePhysics apparatus is there, more or less by default, no need to spell it out.Device ratings are... an interesting property, but not quite in the way you think. Uh, I think?There may be a clearer / more fundamental rule underlying this line of thought, but I'm not quite sure what it is; mainly, I can think of many reasons whynot. That suggests to me that the claim is untrue, or better to say, not specific enough.We must firstly be careful that we're comparing apples to apples. Or, say, crabapples to Golden Delicious, since we're talking  similar devices, but of very different scales and "flavors" (ratings)!Regarding pulsed ratings: this is simply a matter of a design's power density relative to its design cooling capacity.We first need to separate what's commercially available, from what's physically possible:The fact that a tube can dissipate some kW for some ms, or s, or min even, is fairly trivial, or uninteresting, given its scale (10s, 100s of g of material, at several 100s of °C); whether it can dissipate that continuously as well, is simply a matter of cooling available. A conduction-cooled tube might indeed haveundefinedpulse rating: with little enough cooling, it might not handle any (continuous plate) power at all (just heater, if even that)!Likewise, power switching MOSFETs rated for, say 650V 30A, but 100s W continuous, are quite common. Perhaps these could run hotter, or for longer, if the die were intentionally made larger (but this costs more, for no other benefit), or perhaps by making a copper sandwich rather than an epoxy surround, we could better water cool it; but the thing is, it's not a limitation of the technology itself, merely an artifact of what's commercially available -- what's practical in today's market, and economical to produce for it.Conversely, we can produce transistors today that, I'm pretty sure no matter how much water you spray at them, the die will crack or melt due to sheer power density beneath the surface.But so too,we can produce tubes that melt or vaporize the anode due to sheer power density. They're called electron beam welders!So, any such comparison, would have to be weighed based on ultimate V, I, P, t ratings -- SOA -- given a design optimized for such purposes, not just off-the-shelf parts.Off-the-shelf parts can be whatever, depending on what they're designed for, economics of their production, etc. Peak power can only be less than optimal for the technology; but by how much less, is arbitrary.There's also a source of confusion, from the fact that tubes exhibit numerous degradation mechanisms, which scale poorly with operating conditions (maybe, quadratically, say?). This means significant excess capacity is required, simply to offer reasonable life: a commercial tube might last for say 2-5khr at ratings, but maybe its ultimate operating capacity is 10 times that; but if actually used at that level, it might last 10^2 times shorter, or a higher exponent still. Whereas semiconductors might operate on the bleeding edge for 10k's of hrs, but might degrade perhaps exponentially faster as ratings are exceeded.We also need to be careful not to compare apples to, say, blackberries. The apple is monolithic, homogeneous; the blackberry is made of many segments working together. A microwave transistor is most analogous to planar triodes, which achieved comparable ratings (say, operating at 200V and 100s of mA, good for a few hundred W, maybe a bit over a thousand peak?), at reasonable frequencies (low GHz), albeit at low bandwidths (low 100s MHz -- still very much narrowband tuned circuits). Single MOSFETs are available with analogous ratings; but they're also available at many times higher bandwidth (low ~GHz might be baseband still), let alone center frequency (100s GHz?), say in distributed amplifiers. Going up in power is difficult, but so too was it for lumped-equivalent amplifying tubes, where combining and matching networks were also necessary.We certainly cannot compare microwave transistors to magnetrons or gyrotrons, which use bulk fields rather than point voltages/currents. Transistors likely have the higher power density, but it's much trickier to treat them as distributed or bulk systems; they don't scale as easily, you need matching and phasing networks all over.The closer semiconductor equivalent to these would probably be optics in general: free waves in bulk materials, or constrained in various ways (surface or plane boundaries, waveguides, etc.). Which are themselves often semiconductors -- albeit not of the conventional PN types, not for purpose of electron/hole drift current flow (LEDs/laser diodes being the exception: the union of both, more or less).---*Shrug*, this amount of thought almost certainly wasn't expected from the prompt; but it's interesting how much, and in what ways, the technologies are similar, and not!QuoteI think I just dropped in a few, actually... give or take if that counts as physics apparatus still, hehe.There are some relatives of the above, too: photoemissive, or hot-carrier emissive, semiconductors, i.e. light or applied current causes electron emission; and conversely, electro-APDs where electrons come in through vacuum and strike an APD for extreme gain. I... don't know how commonly used these are, I'm pretty sure they're pretty specialized, and I'm not sure exactly when or where you'd choose one, but, suffice it to say Hammamatsu has made some peculiar devices over the years. The latter, I think is alternative to the traditional photomultiplier?Hot carrier emission is interesting; given enough electric field (usually in or near avalanche breakdown), carriers can be accelerated to energy levels much higher than the band gap, i.e. levels deep in the conduction band (or holes low in the valence band). In MOS circuitry, this is used to deposit charge in EEPROM cells, or it causes a degradation effect in power MOSFETs (or, well, EEPROM degrades with use too, so, that's true regardless, huh?): the excess energy allows carriers to tunnel through an energy barrier, in this case gate oxide. Well, done close enough to the surface, electrons can tunnel out of the material entirely, to the vacuum state; perhaps give or take some additional push from surface electric fields.Conversely, particles striking the semiconductor induce pair production (electrons and holes), with obvious consequences for detection (or indeed generation, as in betavoltaics).So, weird hybrid things.You might consider tube cameras (Vidicons etc.) as hybrids too, as the photosensitive surface is a semiconductor. Not that these are in use today, of coursePlasma TVs might be considered tubes, albeit not hard vacuum but gas-filled; largely obsoleted by LCD and OLED advancements today (I think?), but an interesting stepping-stone technology.Tim

author: jonpaul
author_rank: Super Contributor
timestamp: October 30, 2023, 01:52:26 pm
content: Historic recreation of first ADC 1942 SIGSALY Quantizer Feb 2019 2050 Thyratronshttps://spectrum.ieee.org/rebuilding-a-piece-of-the-first-digital-voice-scramblerhttps://spectrum.ieee.org/sigsaly-analogtodigital-converter-construction-and-debuggingJon

author: coppice
author_rank: Super Contributor
timestamp: October 30, 2023, 01:58:36 pm
content: Quote from: S57UUU on October 30, 2023, 05:34:20 amIts hard to imagine TWTs going away in spacecraft. They work so very well. They can be built to last for many decades with almost zero failures. Maintaining a good vacuum is irrelevant. There is no need to use lead shielding, like TWTs in terrestrial use, as there is nobody around to be hit by the x-rays. So, no serious weighty bits. They just work.

author: coppice
author_rank: Super Contributor
timestamp: October 30, 2023, 02:05:57 pm
content: Quote from: T3sl4co1l on October 30, 2023, 09:59:03 amFor instrument amps tubes have engineering merit, as they produce the specifically distorted sound that people like guitarists love. Nothing else naturally matches them. You need to use elaborate DSP techniques to approximate them, before guitarists start to feel happy about the result of using anything but tubes. Maybe they are just living in the past, following a secret desire to sound like Jimi Hendrix who only had tube amps to work with, but that's want they want from an amp.

author: TimFox
author_rank: Super Contributor
timestamp: October 30, 2023, 02:20:22 pm
content: Quote from: coppice on October 30, 2023, 02:05:57 pmUsing tubes without feedback in a guitar amplifier is analogous to using physical pipes in a church organ: fancy DSP can simulate the sound of a pipe organ, but pipes work well for the purpose.

author: Bud
author_rank: Super Contributor
timestamp: October 30, 2023, 03:06:43 pm
content: This type of satisfaction through emulation will never happen. It is like making FPGA based retro computer emulators. Most people consider it fake. Real hardware is part of the fun.

author: JohnG
author_rank: Frequent Contributor
timestamp: October 30, 2023, 03:23:55 pm
content: Here's one for the list:X-ray tubesNote that the highest power X-ray tubes made in volume have a rotating tungsten anode in the vacuum, because while operating, they can have an electrical input power > 100 kW (1A @ 100 kV). This power is concentrated in less than 1 cm^2 and this would cut right through a stationary piece of tungsten like it was butter. IIRC, the conversion efficiency is on the order of 1%, so only about 1 kW of X-rays are being generated at the source.Note that you will find such tubes on a large rotating platform inside the torus of a typical CT machine. It will give you something to contemplate if you ever are getting a CT scan.Much higher power X-ray tubes are used in industry to look for flaws in giant castings.John

author: S57UUU
author_rank: Regular Contributor
timestamp: October 30, 2023, 03:35:38 pm
content: Agree. So:5. X-ray tubes I do not know of any semiconductor device which would produce Xrays. Maybe Teslacoil knows some?

author: magic
author_rank: Super Contributor
timestamp: October 30, 2023, 04:36:01 pm
content: How long till X-ray LEDs?editIt looks like state of the art experimental UV LEDs are near 200nm at this point, so still an order of magnitude away...

author: coppice
author_rank: Super Contributor
timestamp: October 30, 2023, 04:40:16 pm
content: Quote from: magic on October 30, 2023, 04:36:01 pmAre they even feasible without new semiconductor materials? Existing materials generally need to be kept away from strong x-ray doses or they degrade.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: October 30, 2023, 04:55:28 pm
content: 1) A hot filament electron emitter in vacuum in combination with some electrodes? You could include various ion sources used in mass spectrometry, low pressure sensors, gas analyzers etc.2) Vacuum tubes are still useful in a heavy radiation environment where semiconductors would have a lifespan of a firefly comparing with a glass and metal construction of a tube.CheersAlex

author: TimFox
author_rank: Super Contributor
timestamp: October 30, 2023, 05:15:25 pm
content: RCA published information on the resistance to neutron radiation of their Nuvistor vacuum tubes.https://archive.org/details/bitsavers_rcanuvistoubesForIndustrialandMilitaryApplications_2971514Contained in this summary report of radiation problems in early semiconductor devices are two abstracts from Douglas Aircraft in 1963 of such measurements, where Nuvistors were used as part of the lab setup because of their radiation capability. See pp 74 to 78 ofhttps://apps.dtic.mil/sti/tr/pdf/AD0464309.pdf

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 30, 2023, 07:30:00 pm
content: X-rays very much along the lines of physics things; but being production items, definitely count.I suppose everything electron microscope too; much lower quantity, but production nonetheless. Maybe lump that in with e-beam welders as focused cathode sources? They typically have replaceable cathodes, since inevitable gas in the large drift chamber causes ion bombardment and wear/contamination. Whether from the test article (random samples not baked out), or by means of an entire aperture open to atmosphere (there are, in fact, e-beam applications with outputs in air; the ensuing plasma is used to help maintain the vacuum, making a plasma force-field of sorts).No, nothing you can do with semiconductors; almost by definition. The binding energy is some 10s eV, let alone the bandgap (to free space let alone within the material); by the time you had electrons going that fast, you're liable to lose whole atoms, and now you're sputtering or whatever, and wear occurs. X-rays involve inner electron orbitals: deep, deep in the valence bands, thoroughly occupied, you can't do anything with holes at that depth. The closest analog is Auger electrons, where, on a deep shell being impacted by an energetic photon, the resulting vacancy is filled by a higher-up (lower energy) electron, which by its own kinetic energy, kicks off another (one or more) electron; these can have keV of energy so can be emitted. In other words, low-energy beta radiation in response to x-ray radiation.Likewise, anything deep UV, there's simply nothing thatcanhave such a wide bandgap, you'd be talking electrons transitioning directly between ground and vacuum states. But there's no characteristic energy associated with that, only a minimum; so you get a continuum. In other words: the inverse photoelectric effect. Which... I forget if there's anything actually about that, and one page just says it's basically bremsstrahlung (which is how x-ray tubes work, the sudden stopping of an e-beam kicks out broadband x-rays up to a limiting frequency).There's also tricks like this,https://en.wikipedia.org/wiki/Inverse_photoemission_spectroscopywhere, not so much bulk conduction and fields and stuff apply, but localized to the surface, where weirdness can occur.Effectively, this can probe the hanging molecular bonds of a broken mega-molecule, which can therefore have interesting responses. Many solids can be described as highly-bonded polymers, hence having a rigid crystalline structure (or glass; silica-based glasses for instance can very much be understood as polysiloxanes (silicones) with the -anes substituted with still more Si-O-Si bonds -- hence the rigid and brittle rather than rubbery flexible character!), but that surface being ambiguous and receptive to molecular bonding as well as electronic interaction.Needless to say, these cases also exceed the excitation or ionization energy of any gas, and therefore must be done in vacuum as well. That's basically what it comes down to: anything dealing with higher particle energies (than some ~10eV) must be evacuated.The latest (EUV) semi fab tools are evacuated for exactly this reason; actually they may have been for some generations already? Either that, or filled with a high enough "bandgap" liquid or gas that the previous generation excimer lasers (193nm?) didn't cause problems. Atmospheric oxygen for example absorbs strongly in the 200nm range, hence ozone being detectable above quartz mercury lamps (254nm). (N2 I *think* is suitable? Hmm, yeah probably.)Tim

author: twospoons
author_rank: Frequent Contributor
timestamp: October 30, 2023, 09:17:08 pm
content: Vacuum tubes are still fairly popular among tesla coil builders. A high power vacuum tube oscillator is a much simpler beast than a semiconductor one.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 30, 2023, 09:23:34 pm
content: Quote from: magic on October 30, 2023, 04:36:01 pmSounds like something that would save the planet.

author: jonpaul
author_rank: Super Contributor
timestamp: October 31, 2023, 08:00:55 am
content: Microwave: 100s KW>>Megawatt klystrons for radar, broadcast , particle accelerators eg CERN, SLAC.EHV Power distribution and transmission: Vacuum circuit breakersNuclear research, device triggers, flash lamp triggers: Pulsed HV switches : gas filled , Not vacuum but still tubes.... 3 electrode gas triggered gapsFlash lamps : usually Xenon filled but still (2..3 electrode) tubesHigh power for studios, and laser excitationPulsed HV switchesEnjoyJon

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 31, 2023, 12:59:33 pm
content: Winter's coming, my Tektronix 547 keeps me warm in style.

author: David Aurora
author_rank: Frequent Contributor
timestamp: October 31, 2023, 11:30:59 pm
content: Quote from: coppice on October 30, 2023, 02:05:57 pmI think a huge reason they won't go away is that the serviceability of them for music can't be understated. I've stood on stages and in studios and ripped apart and repaired blown tube amps in the time it took for a stage changeover or to tune up the drums. That just isn't an option with any solid state amp I've seen, due both to the usual failure modes as well as the construction. Being able to just pull out a bad device and pop in a new one is unbeatable. They also tolerate failure extremely well and usually don't need more than new tubes and fuses, where a similar failure in a solid state amp will mean board removal, desoldering/resoldering, replacement of surrounding components, often repair of damaged traces, etc.There's also the simplicity of keeping stock. With basic stock of some 12AX7's, 6L6's and EL34's I've got spares for the vast majority of amps that come through. With the solid state stuff (particularly class D) it's almost impossible to keep stock of everything you might need for even 5 different amps at any given time. Not only for the output stages but also due to the kinds of power supplies typically used.

author: themadhippy
author_rank: Super Contributor
timestamp: November 01, 2023, 12:50:26 am
content: Quoteyou've obviously been very lucky and not heard an H+H combo,to change the output transistors undo 2 screws ,pull out the transistor , plug in a new one from the bucket of spares,replace the 2 screws,repeat after next guitar solo.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 01, 2023, 01:59:58 am
content: Quote from: themadhippy on November 01, 2023, 12:50:26 amIt runs just long enough to blow another pair of transistors? What a shitty design.Note the assumptions that underlie the above (not so much this direct quote, but a couple above): in a repair context,the unit has already failed, therefore we are not pulling from a uniform distribution of all amplifiers in use, but those that have already failed. The vast majority of which will not fail on a day-to-day basis, and many indeed of which may last for decades without any service required at all. And the failure mechanisms may range from thermal (basically, what many would count asbad design: unstable biasing, lack of protection, poor ventilation; and perhaps poor sealing in the case of, shall we say... hydraulic attack? Hey, people spill drinks on lots of things all the time, accidents happen (or less accidental, depending on who's throwing what... but that's another matter as well), sure as hell we can design for that too. Poor mechanical construction, lack of rigidity, lack of shock absorption, poorly mounted components; etc.Of course, robustness is its own  problem, and yet another parameter only weakly correlated with price. Ultimately, you get what you pay for, but you need to do some shopping around to find what's actually worth buying: even pro equipment include partial lemons, in many of the above respects. Far fewer, at least, than consumer or enthusiast junk; let alone the average amateur / scratch built junk.Tim

author: Circlotron
author_rank: Super Contributor
timestamp: November 01, 2023, 07:23:17 am
content: Quote from: S57UUU on October 30, 2023, 05:20:11 amWhen you want to make a one off project just for the hell of it. Say, a little radio that you sit next to on a dark rainy night by the fire and listen to far off signals coming through the aether, while you smell the warmth of transformer insulation and dusty tubes and stare at the glow of the cathodes and dream of how people did just the same in the late 1930s by which time radios were pretty well sorted. Electronic stuff doesn't always have to take the cold, hard, most efficient route. It's not against the law to enjoy stuff like this.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 01, 2023, 07:54:07 am
content: Quote from: Circlotron on November 01, 2023, 07:23:17 amI will say, it's easier to make radios with tubes than transistors; the harmonic generation (and thus mixing images) isn't insane, and you don't need a huge number of parts to get sufficient total gain.Tim

author: richard.cs
author_rank: Super Contributor
timestamp: November 01, 2023, 11:47:07 am
content: Not just for microwave, plenty of industrial use for HF amplifiers too - noting that industrial heating is often HF. Places likehttps://www.coaxialpower.com/still make PAs with triodes for this purpose, though in recent years they've started using solid state for the driver. Apparently 40 kW @ 13.56 MHz will defrost a tonne of chicken in an hour.Here it's a mixture of still being a reasonably convenient way to generate that much RF, and being robust to wild swings in load impedance.

author: tridac
author_rank: Regular Contributor
timestamp: November 01, 2023, 12:23:30 pm
content: Still have a few items of tube test gear in the lab. A Fluke 410B 10Kv power supply, with a huge transmitting triode as series regulator, and a 415B, a lower voltage of the same sort of design. Both all solid state other than for the series regualtir tubes and in one, a tube voltage reference. Very stable and low noise output. If it ain't broke, etc, keep the best of the past, while embracing the new...

author: Wolfgang
author_rank: Super Contributor
timestamp: November 01, 2023, 12:46:58 pm
content: A rather exotic use is high quality noise sources. They are a lot "flatter" than semiconductor based parts, and the noise level can be regulated.Look here:https://electronicprojectsforfun.wordpress.com/making-noise/noise-sources-i-have-built/

author: themadhippy
author_rank: Super Contributor
timestamp: November 01, 2023, 01:36:15 pm
content: Quotenot a sax,but have seen a midi controller that looked remarkable like an oboe.

author: coppice
author_rank: Super Contributor
timestamp: November 01, 2023, 01:48:06 pm
content: Quote from: themadhippy on November 01, 2023, 01:36:15 pmLook around enough and you'll find a MIDI controller to suit every kind of musician's well trained use of hands and or mouth and or feet.

author: CaptDon
author_rank: Super Contributor
timestamp: November 01, 2023, 01:52:08 pm
content: In the high power television broadcast industry some tubes from Eimac and EEV are still common. Klystrodes for instance and a type of super fast acting thyratron which is used to dead short high voltage power supplies (10's of kilovolts at a peak of thousands of amps for a couple hundred microseconds) to avoid dumping the full power supply reserve energy into a magnetron, klystron, klystrode, TWT or crossed field amplifier tube which has arced internally. When those protective tubes fire the magnetic field produced by the wiring can hammer the steel cabinets so hard it sounds like a pistol shot!

author: Messtechniker
author_rank: Frequent Contributor
timestamp: November 01, 2023, 01:58:12 pm
content: A mercury arc rectifier might be the next big thing for your living room.Invest now!

author: David Aurora
author_rank: Frequent Contributor
timestamp: November 01, 2023, 10:28:43 pm
content: Quote from: themadhippy on November 01, 2023, 12:50:26 amI've fixed quite a few of them

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 02, 2023, 06:49:39 am
content: Quote from: themadhippy on November 01, 2023, 01:36:15 pmIt does exist of course, and it's Yamaha, even.https://usa.yamaha.com/products/musical_instruments/winds/digital_wind_instruments/index.html

author: James M
author_rank: Newbie
timestamp: January 28, 2024, 03:50:53 am
content: I understand that Extended Interaction Klystron tubes are used when power is needed at mm-wave and into sub THz frequencies.Here's the CPI product page:https://www.cpii.com/product.cfm/4/40

author: MarkT
author_rank: Frequent Contributor
timestamp: January 28, 2024, 08:33:26 pm
content: Vacuum fluorescent displays are still used in quantity aren't they?

author: coppice
author_rank: Super Contributor
timestamp: January 28, 2024, 08:45:56 pm
content: Quote from: MarkT on January 28, 2024, 08:33:26 pmI think they are finally in serious decline. There are LCDs trying very hard to look like VFDs, so it seems people still like the aesthetic.

author: Wolfgang
author_rank: Super Contributor
timestamp: January 28, 2024, 11:09:08 pm
content: Quote from: MarkT on January 28, 2024, 08:33:26 pmIn quantity no, but some stubborn companies like Keysight even build them in their new ROHS-compliant 3458 8 1/2 digit DMM.Same as the 34420A, same as Keysight picoammeters, ...VFDs add a spooky glow to every lab. Some like that

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 28, 2024, 11:54:21 pm
content: Well, beyond the cool factor, no kind of LCD display can have that kind of contrast so be as easy to read from a distance, and OLED displays are not very durable, and while the contrast is also very good, they are often not bright enough to also be easily visible from a distance. Then there are LED displays, which are also not that "modern", and tend to draw more power than VFDs, at least past a certain number of digits. So, not necessarily as stupid as it seems. Just a thought.

author: Wolfgang
author_rank: Super Contributor
timestamp: January 29, 2024, 12:30:34 am
content: Well, ... but VFD need some awkardly high voltages, and they also dont last forever but tend to bleach out. Why not use normal LCDs, they are normally bright enough for lab instruments.

author: 5U4GB
author_rank: Super Contributor
timestamp: January 29, 2024, 10:35:10 am
content: Quote from: T3sl4co1l on October 30, 2023, 09:59:03 amRan into an example of this just today, retired engineer who likes his audio with even-order harmonics so he designed and built an audio system with digital control, solid-state power supplies, and valve ("toob" if you're in the US) amps to get the necessary effect.The other thing is that the final product was at least as much a work of industrial/steampunk art as electronics, which you can't get with a row of TO3s on a heatsink. When I think of the time that must have gone into this...

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: January 29, 2024, 04:34:55 pm
content: Hi 5U4GB,Quote from: 5U4GB on January 29, 2024, 10:35:10 amDidn't you snap a photo? Pictures please. 8-)Does he run his equpment on online-sine-ups's? No? Then he's not serious.... ;->Best regards

author: MarkT
author_rank: Frequent Contributor
timestamp: January 29, 2024, 05:56:18 pm
content: Quote from: Wolfgang on January 29, 2024, 12:30:34 amI suspect for automotive use the large temperature range of a VFD is attractive, LCDs are more sensitive to heat and cold I believe. 36V isn't akwardly high in my book and some work on 12V even...

author: Wolfgang
author_rank: Super Contributor
timestamp: January 29, 2024, 06:01:04 pm
content: Well, modern computers and displays run on 5 or even 3.3V, so 12V or 36V must be somehow generated from that for a VFD. Its possible, of course, but its extra effort.I never heard that automotive temperature ranges are a problem for LEDs.

author: coppice
author_rank: Super Contributor
timestamp: January 29, 2024, 06:01:14 pm
content: Quote from: MarkT on January 29, 2024, 05:56:18 pmWhen did you last see a VFD in a car or truck? LCDs do have a problem with temperature range. I don't know what happens when they are used as the main dashboard display in Siberia or Death Valley, as you first get into the car, but they seem to be fine in temperate climates.

author: uer166
author_rank: Super Contributor
timestamp: January 29, 2024, 07:59:00 pm
content: Quote from: coppice on January 29, 2024, 06:01:14 pmNothing happens, usually you have a heater for those, and the LCDs that don't, heat up via cabin heat anyway.

author: coppice
author_rank: Super Contributor
timestamp: January 29, 2024, 08:14:24 pm
content: Quote from: uer166 on January 29, 2024, 07:59:00 pmOnce the cabin is comfy, obviously the display is too. What happens as you start away at -40C? LCDs can slow down to snail's pace, where the speed gauge would be a useless smear.

author: 5U4GB
author_rank: Super Contributor
timestamp: January 29, 2024, 11:07:12 pm
content: Quote from: Roehrenonkel on January 29, 2024, 04:34:55 pmI did get a few photos but I'd have to check whether he's OK with me posting them publicly, it's a work in progress with some components in pieces/being worked on rather than a finished display piece. No online UPS, just some boat-anchor transformers for the linear power supply.