@@JohnSmith-eo5sp I totally forgot that. They were in the dock bay of the gigantic submarine-eating ship! In my mind, I was thinking of the nuclear device in Goldfinger, but now I'm not even sure which film she mentioned - if it was Diamonds Are Forever, I was doubly wrong!
Ah yes: Proper Lead Paint. It sticks and it's durable, just like the OLD Solder did: Back in the days when a Grid was a Grid, a Plate was a Plate, and The Filament knew what to do.... :-) 73 DE W8LV BILL
I haven't seen one of these in operation since the early 70s! Great to see the inside. In either 1973, or 74, in the UK we were having problems with both coal supplies (miners strikes) and oil, so the power grid was having some issues. I was working as an electronics engineer in one of the production studios at the BBC Television Centre in West London. Although we had two separate feeders from the grid, emergency diesel generators for News, and a supply from the nearby Barclays Bank data centre (they had a pair of Olympus gas turbines that could generate 4 MW), it was decided to bring in a couple of big containerised generators to power the central control area, and at least one production studio. My studio was out of service for maintenance on the HVAC (2MW of AC!), so I and a colleague got assigned to look at the generators and liaise. The generators were a big diesel and an alternator in a 40 foot container. The control panel had two of those frequency meters on. One was connected to the alternator output and the other to the feeder to the load. the generator had a governor, the idea was to match the frequency of alternator output to the frequency of the feeder. At the time I didn't think about how they worked, so it was fascinating to see your demo and how accurate the indication is. They work like tuning forks! I would love to see how they are made. Edited for spelling 28/01/21
Hi Fran, just wanted to say that I suffer from extreme anxiety and your videos / voice help calm me down when things are wound up tight. Thank you for doing what you do.
DSP will probably be more accurate and reliable, as all it relies on is the frequency of its crystal and maybe the voltage of its supply/voltage reference, leaving very little to go wrong/calibrate. However deity help you if you need to program it but don’t have the software or drivers needed to do so.
I did the firmware on a freq. meter in the early 90's. All I did was count pulses the FPGA gave me. It could plug into any source from 5 to 5000v & show 2 to 9999 Hz. Could've gone higher but input impedance got to be too high and we only had a 4 digit display. It was more precise than the expensive signal generator we had.
I'm consistently mesmerized by shutter effects. The moment it started, I knew that wasn't what you were seeing live. I'm also blown away at the ingenuity of pre-computerization engineers to think up these devices. Basically an inverse music box!
Such a great video. I sincerely appreciate that you did not lard it with a recitation of the difference between AC and DC current, or laboriously work out on screen the current that the meter would draw. The cool little device was given center stage and you let it shine. Thanks!
ha, awesome! I love looking at old analogue electronics and trying to brainstorm how they may have designed them to work. Very interesting. You sound quite positive at the moment, compared to roughly a year ago. I hope that continues.
We used to have aircraft ground power units that had one of these on it to indicate that it was providing good 400 Hz power for the aircraft. Everything is all digital now.
Fran, great channel! These were widely used in applications where power frequency was critical to safe equipment operation - be it from a genset or the mains. The "T" in JBT is none other than RL Triplett, of Triplett Instrument. These were also commonly produced in 400hz versions for military and aerospace applications. Nice find!
Fran....I've always had a love of vibrating reed freq meters and have 4 or 5 in my stash and one running on the output of the inverter in my solar system....I'm glad there are others who enjoy such old tech stuff! How much fun!
Thank you for all your wonderful content Fran . I'm always looking forward to your videos The time flies so fast when I watch them Im always hoping they would last longer.
Where I work we used to have a ground power unit that used one of these to indicate the output frequency of the 400 hz AC being supplied to the aircraft.
Another great episode in the panel gear collection! Thanks, Fran. I have always loved really nifty switches, meters, displays, etc. That meter has a pretty odd-ball frequency range. We would expect to see something like 40 to 70 (or 45-65) range To cover the two major global mains frequencies (50Hz and 60Hz) At least your meter is new enough to be labeled in "Hertz" and not the archaic "Cycles per Second" (CPS) The general transition from CPS to Hertz was around 1960 as I was entering high-school and learning electronics in the garage.
Since it doesn't need much current, could you drive it with an audio amplifier into a step-up transformer (such as a regular wall-wart sort of transformer used in reverse)?
I thought about a signal generator and a step up transformer. 5V times 20 is 100V and impedance is 50 ohm times 400 is 20k is nearly an impedance match.
@@goamarty The impedance match shouldn’t be terribly critical given the low frequencies that will be used, but the 50-ohm series resistor on the frequency generator’s output will significantly limit how much current can be delivered to the step-up transformer at a given output voltage. 7.5mA at 120VAC will require at least 75mA, plus losses, at an output voltage of 12V, which should be perfectly doable to drive the display. But a wall wart transformer (OP) would not be a good choice as many contain more than just a transformer since many devices they power expect a DC voltage, so the wall wart will frequently contain diodes and a filter capacitor. But line voltage transformers are easy to come by and any self-respecting electronics hobbyist will almost certainly have a good selection of such transformers already on hand in the common secondary voltages (e.g. 6.3VAC, 12.6VAC, 25.2VAC, etc) with either 120VAC or 240VAC primaries, either as new stock or harvested from discarded electronics.
Only if your output drivers are protected or designed for the emf kick the added xfrmr will add. For the 100v line distributed sound amplifiers ("constant voltage" type, albeit the term is a misnomer) they have protection inherent in their design.
I maintained ground power generators in the Army and we used these to set the RPM of the engines to 60 Hertz. They were mounted on the Control Panel. You need 60 Hertz to keep the clocks and electric motors synchronized. Love watching you Lab.
Ms. Fran, this is so analogue. I really did not expect this to be so non-intricate. I LOVE you involved musical tones describing this. Love you like a sister Big hugz.
I knew how these worked but have never seen one apart. Interesting to see the subleties of making it work well like the shaping and distancing of the pole pieces
A piece of art indeed. And pure genius. One of those things that the moment you see it and get it you know you could have thought of that yourself. In a million years probably, or years, months, weeks of trying dead end ideas, but still. Awesome. Brilliant in its ''simplicity'
My dad had one of those on his boat to help regulate his generator. His only had about five "tuning forks": 59, 59.5, 60, 60.5 and 61 hz. He had a generator run off the shaft of the engine connected by a kind of variable transmission worked by a crank. After leaving the pier, with the engine settled at its cruising revs, a crew member would turn the crank and tune the generator to 60 hz before flipping the transfer switch. Dad had three ways of providing a/c power: "shore power" provided by an extension cord for use when the boat was tied up; an Onan 5kw diesel generator for use when at anchor; and the shaft generator for use when underway. There was a transfer switch to switch the boat's system from one mode to another. This video is the first time I had a chance to see the inside. The resonators weren't "forks" at all!
that's it fully working lol, it doesn't look so great combined with the cameras framerate so it appears to grow and shrink whereas in reality you just see a single unmoving blurred line
My late father, who was an electronics technician back in the mid-60s/ early 70's for Hewlett-Packard, would have loved this channel. I think of him when I watch.
I got called on a "low voltage generator" back in the 70's. Those meters will also respond to harmonics. They were running the generator at half speed.
The moment you opened that up I said to myself, "It's completely resonant!" Pure and simple. Also Fran, you have everything you need to make a variable frequency driver for this doodad. Just grab a cellphone, signal generator or whatnot, an amplifier, and a 120v-6v step down transformer. Use the amp to drive the transformer in reverse. The load is small, and that'll work a treat!
I work in the testing department for an electric utility company. I have equipment that is absolutely perfectly suited to demonstrating the other frequency tines. I'm not a youtuber but if you want to trust a random internet stranger I would love to borrow this thing so I could get you some footage of it reacting to different frequencies.
As some others have commented, even a modest audio amplifier will run one of these through a suitable step-up transformer e.g, using an audio output transformer "backwards".
If I die of Vanity, promise me, promise me That if they bury me some place I don't want to be That you'll dig me up and transport me Unceremoniously away from the swollen city breeze Garbage bag trees, whispers of disease And acts of enormity And lower me slowly, sadly, and properly Get Ry Cooder to sing my eulogy
Cool! I found one of these a while back, but it was set for the 400 hz frequency that an airplane's power system uses. I hooked up my signal generator to a small audio amp and a vacuum tube output transformer to power it. It was really interesting to see how each of the reeds reacted to differing frequencies.
Thank You for another great video ! Saw a few of these years ago during an equipment upgrade at a military base, along with other old school power equipment. That stuff lasts forever 💝
@@LeifNelandDk Your average remotely modern UPS (say, past 20-30 years) is almost certain to be frequency locked to either a quartz crystal or ceramic resonator, so they actually tend to be quite stable to within +/- 0.1 Hz, or better. So not nearly enough variation to see this meter ever change frequency since you will need at least +/- 0.5 Hz change to see a significant change from one tine to the next since each tine corresponds to a 1 Hz change in frequency. However, the modified square wave (what modified sine really is) output of cheaper UPS’s may have enough harmonics in their output to generate some curious artifacts if the tines can also respond to resonance at higher frequency harmonics as well.
@@eDoc2020 I have a similar model that I still use to test generators I own. Its slightly smaller and only covers 56 to 64 hz. I don’t remember if it says Hz or cycles on it but its quite old. Most my generators produce around 62 hz unloaded the are governed to 59 to 60 hz under decent load, just my old Coleman with Briggs & Straton engine 2,400 Watt generator and Onan travel trailer generator.
It is absolutely a piece of electro-mechanical art as you say. I'm always amazed at what engineers could do with electromechanics during that era. Of course nowadays it would be a Chinese digital display and would no doubt show the information potentially more accurately and be crystal time based etc but this is a marvel of engineering. Glad you appreciate it as I and many other do!
I've seen many that were labeled "cycles." One military surplus vendor I knew never said "Hertz," he always said "Cycles." EG "that's junk, it's 400 cycle." Back in the 70s, before modern power electronics, 400 cycle transformers and motors weren't of much utility to the hobbyist.
If it were "new" then it would say "Made in China".... But it says "New Haven, Conn. USA". It's been "CT" for many decades now. JBT was founded in 1939 and lasted at least into the 1970's. CH took over their switch line in 1976. I don't know what happened to the rest of JBT.
@@scottmarshall1414 And it didn't fully transition to "Hertz" until circa 1970 or so. I was born in 1960, and I remember "Cycles" being used almost exclusively until I was about ten years of age.
Hi Fran. You're right. They built them the way they did because that was the way they did it! And how the technology of the time allowed. I'm finding all these "elder" gadgets to be rivotoling fascinating. I wish, where possible - or the buyer would allow - that you could put source links in. Regardless of that little niggle, please keep up the great old stuff. You are on a real roll right now! Love it!
@@hentaihero2201 He meant air acting as force fields on hair or "straws" that are differently tuned, while this instrument used magnetic fields to produce the vibration.
El wrongo! Ear drum transmits complex sound waves into electrical nerve impulses to the brain. There’s also a very advanced X-Y-Z axis G force detection mechanism that emits electrical nerve impulses for humans to maintain balance and walk upright.
That was the first thing I thought when she started talking about the similarity to guitar pickups - I bet that thing could make some really interesting sounds. It's basically an electric thumb piano!
I've seen reed type frequency meters similar to this that are used as tachometers on small engines to set idle speed, and adjusting the engine's maximum RPM for the governor. They are completely mechanical, and are held against the engine itself to pick up the vibrations which in turn make the reeds vibrate accordingly. They are quite precise, and also quite expensive.
You don't suppose Fran might have a guitar amp laying around that could probably fry that frequency monitor if she wasn't careful? I suppose a bass amp would be ideal.
I’m jealous Fran!! That’s a real nice meter!! I run a couple of old generators for backup power here in Alaska. Most of the paint has fallen off of mine but they still work.
Fran, just connect a power transformer with a 12V secondary backwards. Connect the 12V winding to the speaker output of an audio amp and the 120V winding on the meter and feed an oscillator into the amp. The meter draws less than a watt so no problem. I have seen many of those meters on standby generators in telephone exchanges I used to work in here in New Zealand. The meters had the brand name Framm, probably from the UK as the telephone switching gear came from there. One telephone exchange I worked in had 3 diesel powered standby gen-sets. When a mains power cut happened we had to get the first one going and set the voltage and frequency (with the tine meter) then connect it online. Next get number two started and set voltage and frequency but it needed to be in phase with the first one before connecting online. We had a pair of light bulbs which pulsed, one on the line and the other on the local alternator and we had to get the timing just right before throwing the (totally exposed) knife switch to connect online. The same procedure to get the third one running. Once online they keep each other perfectly in phase of course. The knife switches had badly scarred and melted bits on the contacts due to techs getting the timing wrong.
I was gonna suggest this. if you can find an old audio step down transformer from a valve amp, might work better. they have an air gap if i remember correctly to make it more linear, but a regular transformer would be fine for your test. as you said, not much current draw. a modern transistor amp should have a reactive load protection. or also maybe a step up transformer used for audio distribution in a building - do they still make those?
I've seen those on some older (60:s,70:s I think) generator sets, they were used to set the engine RPM for correct frequency (50 Hz here in Europe). When I served in the Finnish military in the early 90:s we still used portable (ok, relatively portable, weighed about 100 kilograms and needed two men to carry. Fortunately they had nice folding carrying handles so not too bad unless you had to carry them for a long distance) gasoline generators that had those and the starting procedure included checking and, if necessary, adjusting the frequency before plugging in the load. They also had 2-stroke engines so loud, inefficient and smoky and you had to remember to mix oil in the gasoline. Also saw one on a larger diesel generator (200 KVA or thereabouts) made in the 60:s that was used to run a rock crusher at a company I worked for in the early 2000:s. By the way my father had a TI calculator just like that back in the 70:s, I loved playing with it when I was a child.
Physically mount it to a speaker driver and it will oscillate mechanically. The thing is, it's actually able to do the equivalent of an FFT! Feed the driver a complex signal that's a mix of frequencies in the instrument range, and it will neatly isolate them. Also, since it uses less than 1 W, you can feed an amplified signal generator output to a suitable step-up transformer. I suspect a bass amp may be up to the task. While shaking it will yield the FFT-like effect, I'm not sure you can electrically drive it with a complex signal due to possible coil electro-mechanical design optimizations to eliminate possible line/load harmonics, though it would certainly be safe to give it a try! As for the finger resonances, my bet would be a depth taper on the brass mounting block, allowing the fingers to be of uniform construction.
Never seen one of these before, and it's Genius in it's simplicity. I just saw the first shot of the teardown, and can instantly see how it works. Love seeing stuff like this. ;) Basically a row of mini tuning forks, and the coil affects all of them, but they respond mainly to their own natural resonance.
@ 6:24 the resonant frequency tuning is done at the end of the the tines. You can see the size of the solder on the end. The more solder the lower the resonance. You can see that clearly @ 4:15. And you can still find these frequency meters on older vessels.
Do you not have a sig-gen ? It's a pretty high impedance load, so a signal generator would do the trick. With an arbitrary signal generator (programmable), you could 'modulate' AC over 55 to 76Hz, and create a sine wave with the indicators! a 100v PA amp would be perfect for it as well..
As an Electrician's Mate in the Navy, we used those on some ship's generators!! Very robust obviously. We used it to adjust the frequency of shipboard generators. I've also seen them since then in some emergency generator installations. That number on the side, xxxx-xx-xxx-xxxx looks like an NSN (National Stock Number). Each grouping breaks down into codes for the DoD stock system. When I worked in Navy Cal. lab, these were a 'go / no-go' cal. If it read 60Hz when hooked up and wasn't obviously damaged, it passes, and otherwise failed. Nice review. :)
There was a similar instrument in the repair shop I worked at in the mid 1960s. This shop serviced electric shavers. It had the same "reeds" for indicators and you would press it against the running shaver and the reeds would oscillate at the "speed" of the cutting heads.
Nice find, Fran. They are used on portable petroleum powered generators for power supply in the field. If you can connect it to someone's generator you should see the tines form the same wave pattern that the numerals are in. Make the generator react a bit by turning a device on and off, you will see the peak dance around until the generator stabilizes. As several other commenters have said, generators for aircraft use have those for 400 Hz. Your digits on the side of the meter are actually one stock number xxxx-xx-xxx-xxxx. The two-digit segment indicates country of origin, 00 and 01 being USA made.
So, I am very familiar with these. We used them on Aircraft External Power Supply units up until we got fancy new computer controlled units about 5 years ago. They are absolute genius little gauges. I remember that it was always a source of pride to be able to tune in the power supply to the right frequency in the least amount of time. Great video as always :) I wonder if this is from a military parts stockpile from when all of the old manual power carts got retired. Probably not, but it wouldn't surprise me.
Those "tines" are usually referred to as reeds. It's known as a mechanical reed frequency meter. I'm sure they were common in all kinds of power generating applications, but I've seen them mostly in generators where the speed of the engine (governor) had to be adjusted to maintain a 60hz frequency. Super-simple tech, yet accurate and foolproof! I loved seeing you take it apart so we could see the insides. I've never had the opportunity to do that.
Hey Fran, you got a tube amp(I hear it played all the time, in the laaaaab) you got a cell phone, a frequency generator app is free, disconnect the speaker driver, hook the freq analyzer to the output of the output transformer, hook your phone to the amp input, viola! Variable frequency on the cheap, or use your guitar, notes A1-D#. I use a freq app on my phone to my car amp to hunt down resonant panels, and to find the clipping limits. A valve amp is just a low power var. freq. drive, and loading the output xfmr. to a 16kohm vs. a 8-16ohm load for quick funsies wont harm either device at all.
As a pilot, I knew exactly what this was! The very first radio navigation indicators in the early 1930’s had a “tuned reed” indicator that would vibrate one or both of two reeds to indicate whether or not you are left or right of course on the old four course radio range. Commercial pilots preferred the indicator, because the alternative (used by the army) was to constantly listen to an A or N in Morse code over headphones (kind of irritating after a while). I’ve always wanted to see inside one of these type devices. Thanks!
I have an ex-military ISO Comms shelter which has a pair of these on the main power input panel. One is set is for 60Hz and the other is for 400Hz. This shelter was built in the mid eighties for the military. It was usually powered by huge gensets and one way to monitor generator issues was by watching the frequency meters. A lower frequency signaled the generator was running slow and would also cause a dip in voltage and the opposite was true if one observed a higher frequency, the voltage old run high as well. The 60Hz side was used for powering the lighting and climate control system while the 400 Hz system was used for powering a special 28VDC power supply for the radios. These were both three phase systems. At 400Hz the transformers needed to provide the low side are far smaller than those needed for 60Hz systems. Also the filter caps are physically smaller since everything runs at the higher frequency. Its just like in modern switching supplies that can provide high output current without large transformers and caps found in the classic linear power supplies.
Great content as usual. Was the 007 film the Spy who loved me? Detonator from warhead removed to blow up the the shields for the bridge on Strombergs ship. The film couldn’t be more different from the book, where James Bond was an ancillary character who joined in at the end of a very different story. Anyway, Franlab is one of the very best TH-cam channels.
When I was an intern at the erstwhile Uitenhage municipality electricity department in South Africa during my summer university break in 1997, I saw one of those vibrating reed frequency meters in the electrical distribution control room. The municipality didn't have its own generation, so the meter didn't serve a purpose. An engineer explained to me how it worked, which I found interesting. They also still used an analogue chart recorder for logging the total load of the town onto paper rolls. It looked a bit like an EEG or a seismograph. The tech was already considered obsolete at the time, but it worked. Years later, I'd seen similar frequency meters and chart recorders in the control rooms of decommissioned coal-fired power stations.
Thanks Fran. I was in the Army in 1971 and I used a 35 kw generator to power the test equipment van for the Pershing missile. The generator had a simiar gage and was used to trim the frequency to exactly 400 hz by adjusting the govenor. I never knew how it worked. I was guessing it was the vibration of the diesel engine. Now I know how that mysterious gage works. 50 years a mystery and solved.
The angled plates make it so the magnetic force is stronger at one end and weaker at the other. This is needed because the tines are stiffer at one end (high frequency) and more flexible at the other end (low frequency). This notion should resonate (pardon the pun) with a guitarist. The purpose is so that all the tines move up and down approximately the same distance.
I remember these reed type freq meters. When I graduated with my engineering degree, I worked in Marconi’s special services decision, where I specialized on military equipment. Their rule of thumb was if it costs less than 50% of a new unit to repair and to bring into calibration, then repair it. I was surprised at how old some of the technology was that I worked on. One of them was this type of meter. Interesting how things were designed before solid state (and yes, I even worked on a lot of tube electronics!).
In case this wasn't included in a previous comment... FYI - number string on back is the EIA code: 442 = JBT and 931 is 1959 week 31 (according to one of the common EIA formats). Nice video!
I still love all that old tech - used to have some of those both 60 cycle and 400 cycle. Those reeds must have an extremely high Q resonance! Those units use less than a watt - you could probably run that at diffent frequencies using a 16 volt bell transformer hooked to the output of a small audio amp with a freq generator plugged into the amp input. BTW Happy New Year
I noticed the angled plates seem to be in a fixed location, so I was wondering how they tuned each tine to exact frequency when you mentioned that each tine has different mass. Changing the smallest and cheapest piece to tune it makes so much sense that I can't believe I thought they would spend time adjusting parts instead. Really neat piece of tech, something I would never need but I could watch all day, thanks for showing us!
Fran, have seen these on older military field generators. They do have governors but do have a knob to adjust the governor when operating under a heavy load. On older aircraft ground power generators the frequency range is usually 360 to 440 hz with 400 hz being in the middle for the target frequency. A lot of these where used on Stewart Stevensen generators and ground power units. As some one mentioned the number being a NATO parts code or standard.
When I did my service in the USAF, we had these installed in generators made in the 50's and 60's. I was always fascinated by them. We were able to adjust the governors on the engines accurately for output frequency.
That's clever. It reminds me of the windup or hand crank music boxes. They use a comb like structure that is similar, although those often have additional weight added to produce a better range of notes.
I have a book printed in the 1930's that described all kinds of 1920's (and older) technology. There already was this kind of instrument described. I also have used it for the usual purpose of synchronizing "my" generator to the power line in the University of Technology lab. There was a little difference in the frequency resolution. For the first, the overall range was much narrower and the vibrating tines were graduated by 0.5 Hz. Moreover, you could see 3 tines vibrating -- one at high amplitude and two neighboring ones at half amplitude at perfect resonance. A little deviation caused tiny difference in the lower and higher neighboring tine amplitudes. So you could interpret around 0.25 Hz variations. However, the generator synchronizing had yet another "trick", rotating pointer meter. It slowed down when the difference between the power line and the generator approached zero. But besides the frequency, you had to tune the phase shift down to zero before hitting the connection switch. If you had a frequency mismatch, naturally a big bang and tripping breakers would result. Yet, the same bad behavior would also happen even at correct frequency, if the phase was not matching. We students were scared to hit the connecting switch, until the teaching assistant showed that the small generator could be synchronized with as much as two Hz difference when done at just before the phase shift meter was coming to perfect match. I also was dealing with the tine frequency indicator in my second summer work at an oil refinery. There was a 25 KW Diesel motor & generator for emergency situations. It had a massive flywheel and a handle. Between the generator and the flywheel there was an electric clutch. It took some 4 to 5 minutes for me to crank the fly wheel to sufficient speed that the clutch could be activated and the flywheel kicked the Diesel motor (and the generator) to speed. The system had to be tested at least once a month.
Hi Fran. I used to use one like that tailored for 50 Hz. During the 80's in the French army, before coupling a diesel generator to the grid, we have to ensure that the generated frequency, depending on the motor rpm, matched the mains frequency... That was quite tricky because when approaching the right frequency we have to switch when the phase match too!... Currently waves are synthesized automatically at the right phase, no more pleasure!
Is that radioactive lume on those tabs?
No. Just good old safe lead paint.
@@FranLab *making homer simpsons drooling face*
"rrrrgh.... lead paint...."
@@JohnSmith-eo5sp I totally forgot that. They were in the dock bay of the gigantic submarine-eating ship! In my mind, I was thinking of the nuclear device in Goldfinger, but now I'm not even sure which film she mentioned - if it was Diamonds Are Forever, I was doubly wrong!
@@JohnSmith-eo5sp is this video actually 59.94 or straight 60 FPS?
Ah yes: Proper Lead Paint. It sticks and it's durable, just like the OLD Solder did: Back in the days when a Grid was a Grid, a Plate was a Plate, and The Filament knew what to do.... :-) 73 DE W8LV BILL
I haven't seen one of these in operation since the early 70s! Great to see the inside. In either 1973, or 74, in the UK we were having problems with both coal supplies (miners strikes) and oil, so the power grid was having some issues. I was working as an electronics engineer in one of the production studios at the BBC Television Centre in West London. Although we had two separate feeders from the grid, emergency diesel generators for News, and a supply from the nearby Barclays Bank data centre (they had a pair of Olympus gas turbines that could generate 4 MW), it was decided to bring in a couple of big containerised generators to power the central control area, and at least one production studio. My studio was out of service for maintenance on the HVAC (2MW of AC!), so I and a colleague got assigned to look at the generators and liaise. The generators were a big diesel and an alternator in a 40 foot container. The control panel had two of those frequency meters on. One was connected to the alternator output and the other to the feeder to the load. the generator had a governor, the idea was to match the frequency of alternator output to the frequency of the feeder. At the time I didn't think about how they worked, so it was fascinating to see your demo and how accurate the indication is. They work like tuning forks! I would love to see how they are made.
Edited for spelling 28/01/21
"idea was to match the frequency of alternator output to the frequency of the feeder." - That's easy, just connect them together ;)
@@millomweb Exactly, I recommend staples.
@@millomweb BANG! "Never mind -- it's just a phase they're going through."
@@edwatts9890 the matter with you ? Oh, you're clumsy !
@@wargamingrefugee9065 3 fairly chunky variable resistors would be better - and a generator running 0·1Hz slow until becoming the power source.
Hi Fran, just wanted to say that I suffer from extreme anxiety and your videos / voice help calm me down when things are wound up tight. Thank you for doing what you do.
Variable frequency mains is easy - signal gen, audio power amplifier and a mains transformer wired back-to-front
Sounds great, now mail it to the Fran lab!
The audio DAC built into almost all devices nowadays also works in a pinch
Basically a bunch of tuning forks
1000 watt DJ amplifier is capable of putting out 115 volts ac on the speaker terminals old 70s Crown amp
@@hellhound-si5oz Ha! I just suggested the same thing before seeing your post. Those Crown amps do come in handy.
This kind of "old" tech always amaze me because is fully made using physics properties, nowdays we mostly use DSP even for trivial tasks.
I used to spend a lot of time taking out old analogue instruments replacing them with DPM's It always felt a bit sad.
@@jrkorman indeed and far more prone to rfi interference too.
DSP will probably be more accurate and reliable, as all it relies on is the frequency of its crystal and maybe the voltage of its supply/voltage reference, leaving very little to go wrong/calibrate.
However deity help you if you need to program it but don’t have the software or drivers needed to do so.
I did the firmware on a freq. meter in the early 90's. All I did was count pulses the FPGA gave me. It could plug into any source from 5 to 5000v & show 2 to 9999 Hz. Could've gone higher but input impedance got to be too high and we only had a 4 digit display. It was more precise than the expensive signal generator we had.
But just remember, at the heart of a digital frequency counter will be a carefully cut tuning fork - vibrating a few million times a second.
I'm consistently mesmerized by shutter effects. The moment it started, I knew that wasn't what you were seeing live.
I'm also blown away at the ingenuity of pre-computerization engineers to think up these devices. Basically an inverse music box!
Such a great video. I sincerely appreciate that you did not lard it with a recitation of the difference between AC and DC current, or laboriously work out on screen the current that the meter would draw. The cool little device was given center stage and you let it shine. Thanks!
Ahhh, my OCD rested in sublime happiness as you used the properly sized blade screwdriver!
ha, awesome! I love looking at old analogue electronics and trying to brainstorm how they may have designed them to work. Very interesting. You sound quite positive at the moment, compared to roughly a year ago. I hope that continues.
We used to have aircraft ground power units that had one of these on it to indicate that it was providing good 400 Hz power for the aircraft. Everything is all digital now.
They're still used in the USAF on the -60 units.
Speak for yourself. We still run our aircraft off an old GPU built in Hobart. No clue exactly when, but I've always been very fascinated by it
Fran, great channel! These were widely used in applications where power frequency was critical to safe equipment operation - be it from a genset or the mains. The "T" in JBT is none other than RL Triplett, of Triplett Instrument. These were also commonly produced in 400hz versions for military and aerospace applications. Nice find!
@Franlab I believe that AvE did a review on a vibrational tach that used the same tech. So cool to see it on a line frequency meter. Awesome stuff!
Fran....I've always had a love of vibrating reed freq meters and have 4 or 5 in my stash and one running on the output of the inverter in my solar system....I'm glad there are others who enjoy such old tech stuff! How much fun!
Luv the classic Ti 30 calculator!!
Thank you for all your wonderful content Fran . I'm always looking forward to your videos The time flies so fast when I watch them Im always hoping they would last longer.
Where I work we used to have a ground power unit that used one of these to indicate the output frequency of the 400 hz AC being supplied to the aircraft.
No dispute that Fran has some of the coolest vintage tech on her lab. I love this thing. Plus anything in bakelite is gonna be cool
Like a Weller solder gun, until you drop it.
👍"Electromechanical artwork." Good description.
It makes me wonder how it might be adapted to a youth oriented science education display.
Another great episode in the panel gear collection! Thanks, Fran.
I have always loved really nifty switches, meters, displays, etc.
That meter has a pretty odd-ball frequency range.
We would expect to see something like 40 to 70 (or 45-65) range
To cover the two major global mains frequencies (50Hz and 60Hz)
At least your meter is new enough to be labeled in "Hertz" and not the archaic "Cycles per Second" (CPS) The general transition from CPS to Hertz was around 1960 as I was entering high-school and learning electronics in the garage.
Since it doesn't need much current, could you drive it with an audio amplifier into a step-up transformer (such as a regular wall-wart sort of transformer used in reverse)?
I thought about a signal generator and a step up transformer. 5V times 20 is 100V and impedance is 50 ohm times 400 is 20k is nearly an impedance match.
@@goamarty The impedance match shouldn’t be terribly critical given the low frequencies that will be used, but the 50-ohm series resistor on the frequency generator’s output will significantly limit how much current can be delivered to the step-up transformer at a given output voltage. 7.5mA at 120VAC will require at least 75mA, plus losses, at an output voltage of 12V, which should be perfectly doable to drive the display.
But a wall wart transformer (OP) would not be a good choice as many contain more than just a transformer since many devices they power expect a DC voltage, so the wall wart will frequently contain diodes and a filter capacitor. But line voltage transformers are easy to come by and any self-respecting electronics hobbyist will almost certainly have a good selection of such transformers already on hand in the common secondary voltages (e.g. 6.3VAC, 12.6VAC, 25.2VAC, etc) with either 120VAC or 240VAC primaries, either as new stock or harvested from discarded electronics.
Only if your output drivers are protected or designed for the emf kick the added xfrmr will add. For the 100v line distributed sound amplifiers ("constant voltage" type, albeit the term is a misnomer) they have protection inherent in their design.
I maintained ground power generators in the Army and we used these to set the RPM of the engines to 60 Hertz. They were mounted on the Control Panel. You need 60 Hertz to keep the clocks and electric motors synchronized. Love watching you Lab.
I have a 800Watt generator from the early 1980’s that has a smaller version of this vibrating reed meter. The gen and meter still work fine.
Ms. Fran, this is so analogue.
I really did not expect this to be so non-intricate.
I LOVE you involved musical tones describing this.
Love you like a sister
Big hugz.
I knew how these worked but have never seen one apart. Interesting to see the subleties of making it work well like the shaping and distancing of the pole pieces
A piece of art indeed. And pure genius. One of those things that the moment you see it and get it you know you could have thought of that yourself. In a million years probably, or years, months, weeks of trying dead end ideas, but still. Awesome. Brilliant in its ''simplicity'
Amazing piece of art. I would love to see it working on different frequencies.
My dad had one of those on his boat to help regulate his generator. His only had about five "tuning forks": 59, 59.5, 60, 60.5 and 61 hz. He had a generator run off the shaft of the engine connected by a kind of variable transmission worked by a crank. After leaving the pier, with the engine settled at its cruising revs, a crew member would turn the crank and tune the generator to 60 hz before flipping the transfer switch. Dad had three ways of providing a/c power: "shore power" provided by an extension cord for use when the boat was tied up; an Onan 5kw diesel generator for use when at anchor; and the shaft generator for use when underway. There was a transfer switch to switch the boat's system from one mode to another. This video is the first time I had a chance to see the inside. The resonators weren't "forks" at all!
That's astonishing! Oh, and it looks like there's actually a tiny bit of response from the 59Hz indicator.
that's it fully working lol, it doesn't look so great combined with the cameras framerate so it appears to grow and shrink whereas in reality you just see a single unmoving blurred line
My late father, who was an electronics technician back in the mid-60s/ early 70's for Hewlett-Packard, would have loved this channel. I think of him when I watch.
I got called on a "low voltage generator" back in the 70's. Those meters will also respond to harmonics. They were running the generator at half speed.
The moment you opened that up I said to myself, "It's completely resonant!" Pure and simple. Also Fran, you have everything you need to make a variable frequency driver for this doodad. Just grab a cellphone, signal generator or whatnot, an amplifier, and a 120v-6v step down transformer. Use the amp to drive the transformer in reverse. The load is small, and that'll work a treat!
I work in the testing department for an electric utility company. I have equipment that is absolutely perfectly suited to demonstrating the other frequency tines. I'm not a youtuber but if you want to trust a random internet stranger I would love to borrow this thing so I could get you some footage of it reacting to different frequencies.
As some others have commented, even a modest audio amplifier will run one of these through a suitable step-up transformer e.g, using an audio output transformer "backwards".
@@hughbrackett343 ... you could do that or connect it to a portable generator and vary the throttle to change the frequency.
This has been nice to see in action, ive acquired one myself,inadvertently, and like yours it is of great quality. Thank you!
You may have found a "holy grail" guitar pickup there...call Ry Cooder.
If I die of Vanity, promise me, promise me
That if they bury me some place I don't want to be
That you'll dig me up and transport me
Unceremoniously away from the swollen city breeze
Garbage bag trees, whispers of disease
And acts of enormity
And lower me slowly, sadly, and properly
Get Ry Cooder to sing my eulogy
It's more of a reverse guitar pickup... a guitar putdown?
I just became one of your Patreons. You're real and "down to earth". I hope next month when I start my channel I can learn something from you.
Cool! I found one of these a while back, but it was set for the 400 hz frequency that an airplane's power system uses. I hooked up my signal generator to a small audio amp and a vacuum tube output transformer to power it. It was really interesting to see how each of the reeds reacted to differing frequencies.
Most of the generators I seen in the army had one. Had a knob that you could adjust the frequency with.
Yeah, I still use one on the GPU at the airport I work at.
Thank You for another great video !
Saw a few of these years ago during an equipment upgrade at a military base, along with other old school power equipment. That stuff lasts forever 💝
10:45 just hook it up to an old gasoline generator and you'll see it move around, they are not typically super frequency stable
Or an UPS in off-line mode.
Yeah but I thought they're usually much more stable than this. For a generator I'd expect a range more like 55-65 Hertz.
@@LeifNelandDk Your average remotely modern UPS (say, past 20-30 years) is almost certain to be frequency locked to either a quartz crystal or ceramic resonator, so they actually tend to be quite stable to within +/- 0.1 Hz, or better. So not nearly enough variation to see this meter ever change frequency since you will need at least +/- 0.5 Hz change to see a significant change from one tine to the next since each tine corresponds to a 1 Hz change in frequency. However, the modified square wave (what modified sine really is) output of cheaper UPS’s may have enough harmonics in their output to generate some curious artifacts if the tines can also respond to resonance at higher frequency harmonics as well.
@@eDoc2020 I have a similar model that I still use to test generators I own. Its slightly smaller and only covers 56 to 64 hz. I don’t remember if it says Hz or cycles on it but its quite old. Most my generators produce around 62 hz unloaded the are governed to 59 to 60 hz under decent load, just my old Coleman with Briggs & Straton engine 2,400 Watt generator and Onan travel trailer generator.
It is absolutely a piece of electro-mechanical art as you say. I'm always amazed at what engineers could do with electromechanics during that era. Of course nowadays it would be a Chinese digital display and would no doubt show the information potentially more accurately and be crystal time based etc but this is a marvel of engineering. Glad you appreciate it as I and many other do!
AvE did a video on something very similar, it was an RPM meter, looked the exact same but square.
These indicators are a delight! The repair shop I worked in had several in the old meters drawer, for 60Hz and for 400Hz power.
If it were truly old, it would probably say "Cycles" instead of "Hertz" IMO.
I've seen many that were labeled "cycles." One military surplus vendor I knew never said "Hertz," he always said "Cycles." EG "that's junk, it's 400 cycle." Back in the 70s, before modern power electronics, 400 cycle transformers and motors weren't of much utility to the hobbyist.
If it were "new" then it would say "Made in China".... But it says "New Haven, Conn. USA". It's been "CT" for many decades now. JBT was founded in 1939 and lasted at least into the 1970's. CH took over their switch line in 1976. I don't know what happened to the rest of JBT.
Maybe an artefact of WW1/WW2?
@@scottmarshall1414 And it didn't fully transition to "Hertz" until circa 1970 or so. I was born in 1960, and I remember "Cycles" being used almost exclusively until I was about ten years of age.
Really old? As in egypt and the pyramids.
Hi Fran. You're right. They built them the way they did because that was the way they did it! And how the technology of the time allowed.
I'm finding all these "elder" gadgets to be rivotoling fascinating.
I wish, where possible - or the buyer would allow - that you could put source links in.
Regardless of that little niggle, please keep up the great old stuff. You are on a real roll right now!
Love it!
Fun fact: that's how our ears work too!
130V?! No thank you.
@@harriehausenman8623 LOL!
Sort of in reverse though, turning physical movement into a signal. Evolution really is awesome.
@@hentaihero2201 He meant air acting as force fields on hair or "straws" that are differently tuned, while this instrument used magnetic fields to produce the vibration.
El wrongo! Ear drum transmits complex sound waves into electrical nerve impulses to the brain. There’s also a very advanced X-Y-Z axis G force detection mechanism that emits electrical nerve impulses for humans to maintain balance and walk upright.
Thanks, Fran! That was such a great piece of old school kit!
You can just use a standard audio amplifier and a step-up transformer to drive the instrument.
It will need a watt or two. 😃
That was the first thing I thought when she started talking about the similarity to guitar pickups - I bet that thing could make some really interesting sounds. It's basically an electric thumb piano!
@@paraworldblue You'd need to add a magnetic field to turn it into a generator.
I've seen reed type frequency meters similar to this that are used as tachometers on small engines to set idle speed, and adjusting the engine's maximum RPM for the governor. They are completely mechanical, and are held against the engine itself to pick up the vibrations which in turn make the reeds vibrate accordingly. They are quite precise, and also quite expensive.
55 to 75 Hz. It's just the digits are for even frequencies and soans 56 to 74 Hz.
I was so fortunate to work in Telco in the 70's, where our 53.5V 400A PSU's had those - could stare at them and wonder how they worked. Thanks Fran!
I wonder if they made harmonicas, too! Thanks for this :-)
Yeah, but only 1/64 octave range hehe
I’m really loving these latest batch of videos
yeah I love these things, I found one on ebay a while back
We still had these in all our mobile communications vans in the military through the 90's. Kind of nice to see them again!
hi Fran,
i would use a transformer and an audio amp :3 then use a function generator to vary the frequency
kind regards Lara :D
A 100V loudspeaker transformer would work, I'm sure you have one in stock somewhere.
Or an output transformer from a tube amplifier in reverse.
@@LeifNelandDk Or feed it straight from the output tubes of a tube amp. :)
You don't suppose Fran might have a guitar amp laying around that could probably fry that frequency monitor if she wasn't careful? I suppose a bass amp would be ideal.
I’m jealous Fran!! That’s a real nice meter!!
I run a couple of old generators for backup power here in Alaska. Most of the paint has fallen off of mine but they still work.
That is so cool. Imagine tuning this, need to have a gray beard and your tongue at the right angle.
Fran, just connect a power transformer with a 12V secondary backwards. Connect the 12V winding to the speaker output of an audio amp and the 120V winding on the meter and feed an oscillator into the amp. The meter draws less than a watt so no problem. I have seen many of those meters on standby generators in telephone exchanges I used to work in here in New Zealand. The meters had the brand name Framm, probably from the UK as the telephone switching gear came from there. One telephone exchange I worked in had 3 diesel powered standby gen-sets. When a mains power cut happened we had to get the first one going and set the voltage and frequency (with the tine meter) then connect it online. Next get number two started and set voltage and frequency but it needed to be in phase with the first one before connecting online. We had a pair of light bulbs which pulsed, one on the line and the other on the local alternator and we had to get the timing just right before throwing the (totally exposed) knife switch to connect online. The same procedure to get the third one running. Once online they keep each other perfectly in phase of course. The knife switches had badly scarred and melted bits on the contacts due to techs getting the timing wrong.
The early days of MEMS...
;)
... where the first "M" is for "mini" and not "micro".
@@MCPicoli More like "Macro" :)
that is so fascinating Fran, never knew they existed, what a neat and functional concept.
Hey.
PLEASE ADD SUBTITLES SO I CAN WATCH THIS thx
I love how the oscillation interacts with the camera's frame rate, you can see it cycling through the phase space.
It's the difference between the 60 Hz line frequency and the 59.940 Hz camera frame rate: 0.060 Hz, or one cycle every 16.7 seconds.
Just use a pa amp and a standard 12v transformer backwards to create variable frequency 120v ac
I was gonna suggest this. if you can find an old audio step down transformer from a valve amp, might work better. they have an air gap if i remember correctly to make it more linear, but a regular transformer would be fine for your test. as you said, not much current draw. a modern transistor amp should have a reactive load protection. or also maybe a step up transformer used for audio distribution in a building - do they still make those?
I've seen those on some older (60:s,70:s I think) generator sets, they were used to set the engine RPM for correct frequency (50 Hz here in Europe).
When I served in the Finnish military in the early 90:s we still used portable (ok, relatively portable, weighed about 100 kilograms and needed two men to carry. Fortunately they had nice folding carrying handles so not too bad unless you had to carry them for a long distance) gasoline generators that had those and the starting procedure included checking and, if necessary, adjusting the frequency before plugging in the load. They also had 2-stroke engines so loud, inefficient and smoky and you had to remember to mix oil in the gasoline.
Also saw one on a larger diesel generator (200 KVA or thereabouts) made in the 60:s that was used to run a rock crusher at a company I worked for in the early 2000:s.
By the way my father had a TI calculator just like that back in the 70:s, I loved playing with it when I was a child.
I love my wiggle tachometer.
A ‘sirometer’?
Physically mount it to a speaker driver and it will oscillate mechanically. The thing is, it's actually able to do the equivalent of an FFT! Feed the driver a complex signal that's a mix of frequencies in the instrument range, and it will neatly isolate them.
Also, since it uses less than 1 W, you can feed an amplified signal generator output to a suitable step-up transformer. I suspect a bass amp may be up to the task.
While shaking it will yield the FFT-like effect, I'm not sure you can electrically drive it with a complex signal due to possible coil electro-mechanical design optimizations to eliminate possible line/load harmonics, though it would certainly be safe to give it a try!
As for the finger resonances, my bet would be a depth taper on the brass mounting block, allowing the fingers to be of uniform construction.
so, a VERY limited spectrum analyzer. :0
Never seen one of these before, and it's Genius in it's simplicity.
I just saw the first shot of the teardown, and can instantly see how it works. Love seeing stuff like this. ;)
Basically a row of mini tuning forks, and the coil affects all of them, but they respond mainly to their own natural resonance.
4:07 did...did you say "nook-u-lar"?
Maybe I need more coffee.
It's called an accent. No need to be scared :)
If she didn't, then so do I ;)
@@llamallama1509 It's not an accent.
@ 6:24 the resonant frequency tuning is done at the end of the the tines. You can see the size of the solder on the end. The more solder the lower the resonance. You can see that clearly @ 4:15. And you can still find these frequency meters on older vessels.
Since it's for mains frequency measurement, do you have any view on why 60 Hz isn't centre-scale? Is over-frequency the more likely supply fault?
Do you not have a sig-gen ? It's a pretty high impedance load, so a signal generator would do the trick.
With an arbitrary signal generator (programmable), you could 'modulate' AC over 55 to 76Hz, and create a sine wave with the indicators!
a 100v PA amp would be perfect for it as well..
I love it! I use VFD drives for many of my projects. Will have to try to find a frequency meter like yours to play with and make a video!
As an Electrician's Mate in the Navy, we used those on some ship's generators!! Very robust obviously. We used it to adjust the frequency of shipboard generators. I've also seen them since then in some emergency generator installations. That number on the side, xxxx-xx-xxx-xxxx looks like an NSN (National Stock Number). Each grouping breaks down into codes for the DoD stock system.
When I worked in Navy Cal. lab, these were a 'go / no-go' cal. If it read 60Hz when hooked up and wasn't obviously damaged, it passes, and otherwise failed. Nice review. :)
Thanks for another great video Fran!
There was a similar instrument in the repair shop I worked at in the mid 1960s. This shop serviced electric shavers. It had the same "reeds" for indicators and you would press it against the running shaver and the reeds would oscillate at the "speed" of the cutting heads.
Nice find, Fran. They are used on portable petroleum powered generators for power supply in the field. If you can connect it to someone's generator you should see the tines form the same wave pattern that the numerals are in. Make the generator react a bit by turning a device on and off, you will see the peak dance around until the generator stabilizes.
As several other commenters have said, generators for aircraft use have those for 400 Hz.
Your digits on the side of the meter are actually one stock number xxxx-xx-xxx-xxxx. The two-digit segment indicates country of origin, 00 and 01 being USA made.
So, I am very familiar with these. We used them on Aircraft External Power Supply units up until we got fancy new computer controlled units about 5 years ago. They are absolute genius little gauges. I remember that it was always a source of pride to be able to tune in the power supply to the right frequency in the least amount of time. Great video as always :) I wonder if this is from a military parts stockpile from when all of the old manual power carts got retired. Probably not, but it wouldn't surprise me.
Those "tines" are usually referred to as reeds. It's known as a mechanical reed frequency meter. I'm sure they were common in all kinds of power generating applications, but I've seen them mostly in generators where the speed of the engine (governor) had to be adjusted to maintain a 60hz frequency. Super-simple tech, yet accurate and foolproof! I loved seeing you take it apart so we could see the insides. I've never had the opportunity to do that.
Hey Fran, you got a tube amp(I hear it played all the time, in the laaaaab) you got a cell phone, a frequency generator app is free, disconnect the speaker driver, hook the freq analyzer to the output of the output transformer, hook your phone to the amp input, viola! Variable frequency on the cheap, or use your guitar, notes A1-D#. I use a freq app on my phone to my car amp to hunt down resonant panels, and to find the clipping limits. A valve amp is just a low power var. freq. drive, and loading the output xfmr. to a 16kohm vs. a 8-16ohm load for quick funsies wont harm either device at all.
As a pilot, I knew exactly what this was! The very first radio navigation indicators in the early 1930’s had a “tuned reed” indicator that would vibrate one or both of two reeds to indicate whether or not you are left or right of course on the old four course radio range. Commercial pilots preferred the indicator, because the alternative (used by the army) was to constantly listen to an A or N in Morse code over headphones (kind of irritating after a while). I’ve always wanted to see inside one of these type devices. Thanks!
I have an ex-military ISO Comms shelter which has a pair of these on the main power input panel. One is set is for 60Hz and the other is for 400Hz. This shelter was built in the mid eighties for the military. It was usually powered by huge gensets and one way to monitor generator issues was by watching the frequency meters. A lower frequency signaled the generator was running slow and would also cause a dip in voltage and the opposite was true if one observed a higher frequency, the voltage old run high as well. The 60Hz side was used for powering the lighting and climate control system while the 400 Hz system was used for powering a special 28VDC power supply for the radios. These were both three phase systems. At 400Hz the transformers needed to provide the low side are far smaller than those needed for 60Hz systems. Also the filter caps are physically smaller since everything runs at the higher frequency. Its just like in modern switching supplies that can provide high output current without large transformers and caps found in the classic linear power supplies.
Great content as usual. Was the 007 film the Spy who loved me? Detonator from warhead removed to blow up the the shields for the bridge on Strombergs ship. The film couldn’t be more different from the book, where James Bond was an ancillary character who joined in at the end of a very different story. Anyway, Franlab is one of the very best TH-cam channels.
When I was an intern at the erstwhile Uitenhage municipality electricity department in South Africa during my summer university break in 1997, I saw one of those vibrating reed frequency meters in the electrical distribution control room. The municipality didn't have its own generation, so the meter didn't serve a purpose. An engineer explained to me how it worked, which I found interesting. They also still used an analogue chart recorder for logging the total load of the town onto paper rolls. It looked a bit like an EEG or a seismograph. The tech was already considered obsolete at the time, but it worked.
Years later, I'd seen similar frequency meters and chart recorders in the control rooms of decommissioned coal-fired power stations.
Thanks Fran. I was in the Army in 1971 and I used a 35 kw generator to power the test equipment van for the Pershing missile. The generator had a simiar gage and was used to trim the frequency to exactly 400 hz by adjusting the govenor. I never knew how it worked. I was guessing it was the vibration of the diesel engine. Now I know how that mysterious gage works. 50 years a mystery and solved.
Still in use where I work! A lot of old tech on our boat :) Interesting video, thanks.
The angled plates make it so the magnetic force is stronger at one end and weaker at the other. This is needed because the tines are stiffer at one end (high frequency) and more flexible at the other end (low frequency). This notion should resonate (pardon the pun) with a guitarist. The purpose is so that all the tines move up and down approximately the same distance.
I remember these reed type freq meters. When I graduated with my engineering degree, I worked in Marconi’s special services decision, where I specialized on military equipment. Their rule of thumb was if it costs less than 50% of a new unit to repair and to bring into calibration, then repair it. I was surprised at how old some of the technology was that I worked on. One of them was this type of meter. Interesting how things were designed before solid state (and yes, I even worked on a lot of tube electronics!).
What application for testing line frequency would it be necessary to show a figure quite a bit more higher vs. lower than 60 Hz ?
Amazing..! Many thanks for your time for us. :) (...btw, AGAIN, I LOOOOVEEE the mess in your workbench, LOL..! :)
Very neat stuff, would look good in a nice wood enclosure, cheers.
In case this wasn't included in a previous comment... FYI - number string on back is the EIA code: 442 = JBT and 931 is 1959 week 31 (according to one of the common EIA formats). Nice video!
I still love all that old tech - used to have some of those both 60 cycle and 400 cycle. Those reeds must have an extremely high Q resonance! Those units use less than a watt - you could probably run that at diffent frequencies using a 16 volt bell transformer hooked to the output of a small audio amp with a freq generator plugged into the amp input. BTW Happy New Year
I noticed the angled plates seem to be in a fixed location, so I was wondering how they tuned each tine to exact frequency when you mentioned that each tine has different mass. Changing the smallest and cheapest piece to tune it makes so much sense that I can't believe I thought they would spend time adjusting parts instead. Really neat piece of tech, something I would never need but I could watch all day, thanks for showing us!
Fran, have seen these on older military field generators. They do have governors but do have a knob to adjust the governor when operating under a heavy load. On older aircraft ground power generators the frequency range is usually 360 to 440 hz with 400 hz being in the middle for the target frequency. A lot of these where used on Stewart Stevensen generators and ground power units. As some one mentioned the number being a NATO parts code or standard.
When I did my service in the USAF, we had these installed in generators made in the 50's and 60's. I was always fascinated by them. We were able to adjust the governors on the engines accurately for output frequency.
I love that design as well. It appears that that tang is vibrating in various modes rather than just a single mode.
That's clever. It reminds me of the windup or hand crank music boxes. They use a comb like structure that is similar, although those often have additional weight added to produce a better range of notes.
I have a book printed in the 1930's that described all kinds of 1920's (and older) technology. There already was this kind of instrument described. I also have used it for the usual purpose of synchronizing "my" generator to the power line in the University of Technology lab. There was a little difference in the frequency resolution. For the first, the overall range was much narrower and the vibrating tines were graduated by 0.5 Hz. Moreover, you could see 3 tines vibrating -- one at high amplitude and two neighboring ones at half amplitude at perfect resonance. A little deviation caused tiny difference in the lower and higher neighboring tine amplitudes. So you could interpret around 0.25 Hz variations. However, the generator synchronizing had yet another "trick", rotating pointer meter. It slowed down when the difference between the power line and the generator approached zero. But besides the frequency, you had to tune the phase shift down to zero before hitting the connection switch. If you had a frequency mismatch, naturally a big bang and tripping breakers would result. Yet, the same bad behavior would also happen even at correct frequency, if the phase was not matching. We students were scared to hit the connecting switch, until the teaching assistant showed that the small generator could be synchronized with as much as two Hz difference when done at just before the phase shift meter was coming to perfect match.
I also was dealing with the tine frequency indicator in my second summer work at an oil refinery. There was a 25 KW Diesel motor & generator for emergency situations. It had a massive flywheel and a handle. Between the generator and the flywheel there was an electric clutch. It took some 4 to 5 minutes for me to crank the fly wheel to sufficient speed that the clutch could be activated and the flywheel kicked the Diesel motor (and the generator) to speed. The system had to be tested at least once a month.
Hi Fran. I used to use one like that tailored for 50 Hz. During the 80's in the French army, before coupling a diesel generator to the grid, we have to ensure that the generated frequency, depending on the motor rpm, matched the mains frequency... That was quite tricky because when approaching the right frequency we have to switch when the phase match too!... Currently waves are synthesized automatically at the right phase, no more pleasure!