By the way - Yes, I did see that I had the plug in the "normal" input and moved it over to the "Bass" input to do the test. I just didn't get it on camera.

"Oh, you're a musician? What instrument do you play?" "Power distribution frequency meter."

A mechanical mains electricity frequency meter doesn't need a luminous dial: if you want to know what the frequency is it means the lights are on! If the lights are off, well, I guess frequency is the least of your worries.

I think the people who asked "why didn't you just google it" really *really* do not understand this channel.

"That's not how I learn." 😀 I love the way you learn, Fran!

I work with a camp at a remote site (A wilderness retreat centre), that is on its own hydroelectric power system. As the system is islanded (not connected to the grid) our line frequency is far more variable, depending on load. We have these meters in several locations, including in a box on top of the commercial dishwasher. In the winter months, when the available power is low, one of the jobs of the folks in the dish pit is to keep an eye on the meter, and if the frequency drops too low, they have to quickly power off the dishwasher and hot water booster to prevent a power outage. Our typical line frequency is at around 59.5 Hz in the winter months. If it drops to 58.5, the protection relays on the generating plant disconnect the town. These things are important when your generating plant is only producing 60kW, and your commercial dishwashing system is trying to draw 5kW.

Fran, Transformers have DC resistance which you measured. They also have a reactive component. Those combined is the impedance. The load of the secondary of a transformer is reflected into the primary. EG: unloaded transformer draws little current. Overloaded transformer draws higher current, limited by the resistance. For voltage stability, driving a transformer with a solid state amp with high negative feedback, or a tube amp with push pull outputs works fine. Due to the very high Z of the frequency meter, the small transformer will provide much higher than 8 ohms load to your amplifier. You can test this with a 2nd transformer. Use your variac or another matching transformer and connect them secondary to secondary through an AC ammeter. With line voltage applied to the primary of the first transformer, the low secondary voltage into the 2nd transformer will be low, even with the low wattage frequency meter attached to the 2nd transformer primary. The lower the DC resistance of a transformer, the more current it can handle without high loss due to the winding resistance. The frequency meter does not have an iron core, so it depends on resistance instead of inductance to limit the current. Try it. Use a signal generator, or Audacity on your computer to generate a slow sweep from 55 to 75hz. Turn up the amp to the secondary voltage of the transformer and connect it. If paranoid, fuse it with a 3 amp fuse. An 80 Watt amp is often protected with a 6 amp speaker fuse on solid state amps. Then connect the meter to the primary at 120 Volts. Try it, and use a 3 amp or smaller fuse if you are worried about your amp. You are dropping less than a 5 watt load on an 80 Watt amp. Not a problem. I recommend the 30 watt or more amp is for the voltage. Lower wattage amps can only drive lower voltage transformers and may clip trying to driver 24VAC RMS into the transformer.

As I noted for your original video, the angle of the plates is to ensure the amplitude of vibration is relatively constant throughout the frequency range. Otherwise, the low frequency tines would oscillate at a greater amplitude than those at the high frequency. The tines where the angled bars are further apart get less magnetism, where the bars taper closer is greater magnetism. Whether the mechanical resonance change is achieved by tine thickness, width, or weight of solder (as you noted) does not matter. The "heavier" tines will swing further given the same magnetic field. What is specifically being compensated is the tine weight. And I wouldn't be surprised if when they made their first prototype, this little piece of physics hadn't yet occurred to them. And they scratched their head and came up with a simple and elegant solution.

I have removed dozens of these frequency meters during my years of working on 100+ year-old hydroelectric plants. They were used to bring the generator speed (frequency) to match the running bus to sync before closing the breaker. I have several on my office wall.

Now that's what you call real micro-tonal music!

Impedance and DC resistance are very different things. The primary of your power transformer is about ten ohms. So it draws twelve amps when you connect it to 120V mains? Of course not.

The inverted power transformer trick does work in some cases. Many years ago in college (~1973) I wanted to test a 400Hz aircraft artificial horizon indicator from a Link trainer. I used a 10-watt Heathkit amp and a 12V-to-120VAC filament transformer. Lacking a signal generator, I recorded WWV's 440Hz tone on a piece of open-reel recorder tape and spliced it into a loop. A few adjustments later it worked like a charm!

“Fran Lab Delivers”! Yes!

Thank you for the detailed explanation! I spoke to an older engineer, and he said these are still in place in older power plants. Installed in the 50s, and still working today!

"Fran aren't you smart..." I've learned to ignore those. It's a lot easier to be a back seat engineer. If they know so much they can make their own videos.

The DC ohms of the transformer is not an issue. Measure the transformer on your bassman, it will be less than 1 ohm. It is AC impedace, transformers don't pass DC. The 4-8 ohm load on the transformer imposes the desired load on the final output tubes (something like 3k to 8k ohms depending on the output tube type). Actually when providing the 3-8K load, the transformer itself has a resistance of something like

Fascinating video! Thank you, Fran. The solder on the tines reminds me of a Wurlitzer electric piano. When you purchase a replacement tine (they sometimes break), it comes tuned slightly flat, having slightly too much solder on the tine. You then very gradually file away just enough solder to bring the tine up to the desired pitch. If you accidently file away too much solder and go sharp of the desired pitch, you have to get out the soldering iron and add more solder, then start all over again, filing the solder away, bit by bit, until you reach the desired pitch...a royal pain in the ass! "Playing" the tines on the frequency meter is like playing a guitar string in the presence of a magnetic guitar pickup. The tines of a Wurlitzer electric piano, however, instead of disturbing magnetic lines of flux, use capacitance to pick up the sound. The tines form one plate of a capacitor, and a fixed plate forms the other plate of the capacitor. A charge is then placed on the tines. When the tines vibrate near the fixed plate, it causes a corresponding change in capacitance, which is then amplified. This approach to amplification works the same way as a condensor microphone. And if you want to go on another rabbit trail, there's the Fender Rhodes electric piano, which uses tines that vibrate like guitar strings in a magnetic field. They're easier to tune - you slide a little spring one way or the other on the tine to tune it. I love this stuff! (Sorry for the lengthy post.)

If it had a wider range it could be a true analogue spectrum analysis display!

I love that meter more than I probably should.

The impedance thing is BS. 1: You are measuring the DC impedance, that is not the same as the AC impedance of an iron core transformer at 60Hz. 2: The impedance of the mains line is only a few ohms in order to give you a stable voltage. You don't impedance match your toaster to the mains. The is power delivery, not audio.

Re: Impedance mismatch - this is for people who are interested in how to calculate such things, and some background info. Not to be pedantic or critical or something. There is a big difference between DC resistance and impedance. This is why the transformer doesn't pass 10 amps of current (with its 11 ohm dc resistance on an 110v outlet) when you hook it up. Instead, it draws a few dozen mA to magnetize the core. The 110v/24v transformer is NOT suitable, but other mains transformers are. I ran some calculations, and with a 230v to 6,3v transformer (or 110v to 3v) you can safely drive it with an 8 ohm rated amplifier, as long as the 16000 ohm load is connected EDIT: and is 16000 ohms at 60hz, not at DC. The voltage transformation ratio is 230/6.3=36,5. The impedance transformation ratio is 36.5^2 = 1332. Divide the 16000 ohm frequency meter load by the ratio of 1332, and the amplifier driving the transformer will see 16000/1332= 12 ohm. With the ca. 8mA load at 110v, it will need an amplifier of just over 1 watt, because of the slight mismatch. The DC resistance has no role to speak of, in this application. Tube amps do NOT like driving way too high impedance sources, but 12 ohm on an 8 ohm rated amp will work just fine. The big risk in this case is not blowing up the amp, but blowing up the meter because the amp is able to deliver WAY more power and voltage than needed. With just 10 watts of power you can already produce voltages in the kilovolt range, if you hook up a mains transformer 'in reverse' to a speaker output. I use TDA2003 and 2030 amplifiers for such 'risky' applications. Those are short circuit and open circuit proof. With the 100v or 75v piped audio transformer, you have the same issues. Open circuit secondary, the amplifier will practically see infinite ohms as impedance. Short it out, and it will also see a short circuit even if the transformer says its 4 or 8 ohm (well, it would see just the DC resistance without the impedance added to it). In piped audio transformers, you have to fool around with the watts 'consumed' and that's a whole other story. It's 4 or 8 ohms, if the load is the same as the amount of watts printed on the transformer. Not gonna write more about that now.

Absolutely beautiful way of displaying the frequency, stunning to see it in operation like that. Thank you!

Fran, I just would like to say that I really appreciate your making these two videos. We are about the same age, I’m just a few years younger, and we both grew up with this tech and these early measurement tools that were entirely dependent upon physical properties in order to measure something that would otherwise have required some real electronic tech for the day were always fascinating in their ultimate simplicity and give one a much more hands-on feel for the nature of what is being measured unlike the total disconnect between the physical properties and the actual measurement when measured using counters and microprocessors...not that I would give up any of my more modern test gear, just that these have much more of a 1:1 relationship with the actual physics of what is being measured and give real insights into how things work. Much like seeing a mechanical display of a standing wave is worth far more in terms of understanding and comprehension than an entire book written only with words on the same subject...once you see the physical representation of the property of interest all those words suddenly make crystal clear sense in a way they could not before the demo. So, thank you for both videos, and your great many others I have enjoyed, and just keep being your peculiar nerdy self as we love you dearly just as you are and would not have you be any other way! Also, thank you so much for your narration of all your videos and unique voice as there is something very calming in your voice that I find extremely helpful when struggling with anxiety attacks from Complex PTSD (from a less than ideal childhood and early adult years) and I have frequently tuned into your catalog of videos over the years during such struggles. And a very Merry Christmas to you (and a Happy Hanukkah to Jewish and Messianic friends)!

It will probably be much louder as a pickup if you add a small bias magnet to the tine base

As many others mentioned, you're confusing DC resistance with AC inductance. Sure the secondary on that transformer is 0.6 ohms, but the impedance at 60 Hz will be much higher.

This was so cool! I loved seeing the harmonics as you swept the wave up and down the range. 🥰

Well done Fran for going the extra mile to answer all of the questions. I took one of those meters apart many years ago and saw how it functioned. You learn more by doing that than just seeing it printed in a book or information on the internet. I've also taken apart so many old clocks and aircraft displays years before I realised the dangers of the coatings used.

Anyone who spent hours outside on a cold airfield pan in the 80's/90's, trying to keep warm next to a diesel-powered aircraft power generator set will have watched one of those little gauges. In the UK the power sets were made by Houchin & a selector switch enabled monitoring of the 115v 400hz frequency on each of the three phases.

Fran, resistance (R) mean not impedance (Z). You not consider the inductance (X) of the transformer.

It is mind-boggling when you think about how each & every one of the 21 tines was HAND CALIBRATED...then multiply that by how many of these were made!

A most excellent video! It brought me a chuckle. I watched your last video about it & when you said the coil behind the face was similar to a guitar pickup, I thought OOOOH! she's going to plug it in & jam out. Then I thought, Naaaah! If it could be done, ol' Fran would do it. Now here you are doing it. Simply amazing! Thank you for the follow up video! Regards!

THANK YOU!!! I don't know if it was my comment that prompted that first segment where you played it through an amp (I think a couple other people had the same idea) but seeing you actually do it absolutely made my day, and I wasn't having a great one before I started watching this, so again, thank you! I am an experimental musician, so I absolutely love stuff like this! I might even take some of the sounds and build some kind of music out of them! If you're interested in collaborating on that, please send me a message, because I am very curious to hear other sounds it can make, and I would love to bounce ideas back and forth with you about what it can do musically! Anyway, I paused the video at 4:24 to make this comment, so now I'm gonna watch the rest.

Very cool. I have a Frahm tachometer, which uses very similar tuned reeds like that to measure motor RPM. It's just a box, no wired connections, just sits on the motor housing. Mine goes up to 3600 RPM. I use it for some vibration measurements and I did a calibration Hz to RPM. Frahm also made units that read direct to Frequency. Pretty cool old school frequency measurement device. BTW - I have my TI-30 calculator also LOL. I had mine in HS (1984 grad). There is so much room in the battery compartment that I put a crystal radio in mine (1N34A, etc). I also put a "shocker" in there later on, relay buzzer that would give a tingle, fun little study hall gizmo. Put a bunch of little fun circuits in there. Even had teachers help with ideas back then. I still use that calculator today. Great channel Fran!

Bollocks! The high impedance of the coil will work fine with a transformer . Thats why you can see the output on a scope , drive a electrostatic speaker etc etc etc.

You have an extraordinarily high ratio of Likes to Views. And very deservedly so. Thanks for these videos, I am learning a huge amount and enjoying doing it.

When we used to turn over a few generators, it became apparent that this type of frequency meter was the meter of choice for a lot of manufacturers. From tiny little 300w Honda portables, to 250kW industrials and beyond. Back in the day, the term was 'reed' rather than 'tine' but the meaning isn't lost either way. As well as 'lead loading' to tune the reeds, some makers (cheaper ones) used reeds of differing lengths, which in turn responded to different frequencies. Although these instruments look simple, there is a bit of science behind them, and in the days before electronic frequency meters, these were perfectly adequate for monitoring the mains frequency on the grid. Used in conjunction with a simple 'synchroscope' you had the tools to allow your generating station to match frequency with the grid, and to synchronise phases before tying.

I speculate that angled plates are there to normalize the response of the tines so that all the tines have roughly the same amplitude. Denser magnetic field on the high end helps to push more power to the tines as they would need more power for the same amplitude at higher frequency.

Thanks for the follow-up. It's nice to see how they tuned the vibrating indicators.

Merry Christmas Fran. The frequency meter takes me back to my HV generator days. We used them to indicate when the generator was close to system (synchronous speed) when we could use other instruments such as a synchroscope to match the system frequency and phase. They were magic then and still are. I never knew how they worked until your video.

Sometimes people need to listen to the videos :-). It was cool seeing the output of the meter giving audio. Really cool follow-up

I love watching videos like these. I pause and try to figure out how it operates before the tear-down. Sometimes I get it right (like this time) but often I’m way off. Who cares I love the curiosity and learning that’s why your videos are so great! Excellent work Fran!!!

Now we demand you make a mouth harp pick up coil! :D ;D

Glad you are having a bit of fun with the comments. You have to shovel a lot of dirt to find a diamond. Seems like there are a few in there. Cheers.

My dad got a huge welder/ generator years ago. Someone wanted the dodge 318 engine so we scrapped the generator, it had one of these displays. I had to see how it worked, but figuring out that it was a guitar pickup was beyond me. Great idea

Very appreciative that you came back to this :) great to see it fully in action

Thanks for the video, i did not watch the first one cause I already knew how these operate (having learned about whole Europes power net running in sync). Glow in the dark paint would not make sense for that instrument, since its application would be around some sort of power station, where you could run any incandesent bulb to shine a light -> dark, no frequency, some light, try to get that 50 or 60 hertz thingi somewhat right before connecting to th grid. On a different note, I remember these steam engine governors and a WWI fighter movie, with a simmilar contraption to indicate the airspeed. It was a free spinning airscrew generating a certain rpm dependent of the air flow. The pilot could audible hear his airspeed by recognising the frequency (the higher the nearer to Vmax and ripping of the wing covers). A second indication would be a set of tuning forks (like your frequency counter) that would resonate to the airspeed indicator and would give a objective reading of airspeed, based on the stimulated frequency and independent of the pilots ear. Basically, the rx path of a 9k6 modem would be same, having rc circuits tuned to the tones and detecting a rectified dc to recover the tones to quantified information. A great display of tuning forks in audible range. Thanks and all the best for your endeavors!

The satisfaction of an investigation carried out...it is why there is an entire print industry with just such a genre! Thank you for feeding the minds of thousands upon thousands of subscribers

That last frequency, nice!

Fran, as others have said, a transformer requires an alternating current to work. Measuring its resistance at DC only shows it has continuity. You will need to measure its impedance at say 60Hz in order to calculate its AC resistance at that frequency. Your 24v to 120v transformer would work fine if driven by a 24v RMS 60Hz source . A lower voltage - say 5v - secondary transformer would be better when driven with your amp. An old valve (tube) audio output transformer would be ideal. Love the channel.

You are almost certainly correct on the purpose of the plates. If you want to demonstrate this take any rare earth magnet and measure its holding power.(just rough, even by "feel" will do). Then add a steel washer to the back side and repeat. You will find the hold greatly increased because the steel washer deforms the mag field towards the front. That's why rare earth catches usually come with a steel cup.

lots of great content lately! thanks Fran. Happy Holidays!

thanks for showing off the meter, cant recall having seen one, also interesting was the tuning by weight. When we used to build the acoustic decoders for RC models we created a harp of contacts that we tuned by reed length to get our device channel control separation. It brought back some memories seeing those little wigglers in action, thank you so much. 👍

It was worth it. Learned something from part 1 and part 2! Good on ya, Fran!

it wouldn't appear as 0.6 ohms. It would appear as a ratio of the load on the secondary side. 120:24 is 5:1 winding ratio or 25:1 impedance ratio. You'd need 200 ohms on the 120v side to present an 8 ohm load on the 24v side. 600:8 ohm trafo is 75:1 impedance ratio or 8.7:1 winding ratio. With a 16k load on the 600 ohm side, the amp is seeing a 213 ohm load. I'd be surprised if the DC resistance on either side of that transformer is more than 20 ohms.

Hahah I had a feeling it would work, and the sound is the Hz the tine is, so cool. :) Sounds like something Tool would use on an album lol

Love that Texas Instruments calculator! Takes me back to my childhood c. 1970s-80s. My big brother had one just like it and I envied him! Classic tech that just works.

Transformers have 'reflected' impedance. With a proper impedance meter you'll get an infinite impedance reading on the secondary unless there is a load on the primary. This always seems bizarre when you consider the very low DC resistance of the winding. Of course it works in either direction.

Somewhere I have a tiny, totally mechanical contact tachometer/frequency measuring stick. It looks a bit like a pen or pocket tire pressure test gauge. To use the tool you touch the tip of the stick to something frame, case, or block of a running engine or motor. The stick has a small tab on the side that slids up and down the length of the stick. If you slide the tab it will push or pull a stiff wire out a hole in the tip of the stick. At a specific frequency the wire will suddenly start to wiggle.

Not further forwards with the coil but a permanent magnet to one side of the magnetic material like what forms the back of the coil

Assuming the amplifier you are talking about is tube-based (otherwise - why would it have an output transformer?). Tube amps usually can operate with the output shorted (or too low load impedance) no problem - tubes cannot provide much more current than in normal operation. OTOH, tube amps usually cannot work with the load impedance too high - or there can be voltage spikes that would be bad for the output tubes or the transformer. But, if you already have a tube amp - you can probably take the high voltage from the primary side, couple it trough a capacitor and run the meter this way. As for the power transformer impedance matching - I do not think that works the way you described it. I mean a UPS operates pretty much the same way - low voltage from the battery goes into a transformer to be stepped up to whatever the mains voltage is. Obviously the UPS can work at high load (1kW or whatever it is rated at), but it also works at no load or very low load without any problems. While the DC resistance of the transformer is very low, its AC impedance should be rather high without any load. By the way, I just measured a tube output transformer that's supposed to be 5.2k -> 4R. Its DC resistance is 31R for the primary and my meter shows the secondary DC resistance as zero. But it works normally at audio frequencies :) Also, while audio transformers have their impedance printed, it's only the ratio that's correct. If I take my 5.2k -> 4R transformer and hook up an 8R load to it, the primary impedance will be 10.4k

Hi Fran. Great . I have suggested yesterday (12/17/2020) to use a transformer backwards in the output of an amplifier. I didn't revise my original comments, but I probably didn't specify the usage of an audio transformer, but for sure not even think in using a power transformer - the impedancies for sure wouldn't match. But hey, you got that point, and my "provocation" worked fine also... Thanks, I am a great fan of Fran (it was fun-ny)

I'm not gonna pretend I understand 95% of the electronics talk, it's not my area, but I still enjoy you nerding out over it and I enjoy the nerding out you inspire in the comments too. Keep up the great work!

Hi Fran. I'm really glad you did this second look and were able to show the meter working. Also, I agree with you. It's much better and more fun to figure the "workings" out by oneself, rather than hoping Google spits out an answer. Besides, I've always learned better hands on rather than watching a demonstration.

Hello Fran!! Those frequency indicators were very commonly used in control panels for portable or stationary power generators or alternators. Interesting though that they could generate frequency too!! Fun to see video though!!! Thanks for sharing!!

Nice job with the demonstration. Your explanations and methods are well presented and give insight into how electronics works without getting too technical. The harmonic resonance interference at certain frequencies was an unexpected finding but cool to see. You need a finer vernier on your signal generator to really examine that phenomena more closely... Great job!

Very cool! Thank you for the follow-up, that was worth it just to see how it moves (I couldn't really see it with the shutter speed 60hz on the first one).

It may be louder if you bias the coil with some DC current. Those tines are most likely only very slightly magnetized and tuned to double the frequency they show (they don't have to react to the direction of the field, only the magnitude). Some DC on the coil should play the part of the magnet in the guitar pickup.

Aww, cool! It did not occur to me that the meter would work in reverse as a tiny little electric bass piano, even though it seems so obvious after the demo.

When I worked at a Instrumentation company I calibrated those by adding & taking solder away from the tuning end, of the vibration frequency indicator. Over 42 years ago ! Philip from Cheshire UK 🇬🇧

My idea of just setting it on the speaker would have worked btw. You can see it starts to resonate when you bump the desk etc. Really wished you'd tried that just for the giggles :)

What a triumphant thing, assembling a solution like that from parts "off the shop floor". This one was fun! Thanks!

13:35 - That 0.6 ohms is the DC resistance of the winding. Its AC impedance would be much higher.

I'm certainly not an expert on magnetics, but surely the input/output impedance of the transformer isn't just determined by the winding resistance, but depends on the ratio and the source/load connected? I mean, a theoretical "perfect" transformer has zero resistance doesn't it?

You're one clever lady!

Had to fast forward to see that frequency sweep in action. Instead of saying it does not work, why not just do it!? A 110V to 9V transformer turned the wrong way will generate 110V from a 9V signal generator sinewave. Usually the signal generators can drive 50 ohm loads. This means the resistive load on the other side of the transformer can be as low as 7.5kohm. Now that meter has a huge coil which probably is significantly inductive and have some inductance in addition to the wire resistance, which will lower current further. If your signal generator is too weak to generate 9Vrms sine with 50 ohm source impedance, you can just throw a HiFi audio amp in between (maybe that is what you did - i skipped the boring part). By the way to use the meter as a pickup you need a permanent magnet close to it to get any good signal. Now probably only the earth magnetic field generated the signal. Alternatively put a small DC current through the coil.

I had a tone decoder which worked on the same principles. It had a bunch of reeds at mid-audio frequencies. The NE 567 put them out of business. I had a 400 Hz meter on a radar transmitter. When I converted it to 60 Hz I pulled it out ... I wonder what I did with it.

Some planes had an ultraviolet night light to illuminate the instruments so they would glow a night.

Thanks for the follow up on this. It left me wondering the other day about the width and thickness of the prongs and the direction plates.

I was surprised to be able to hear the 20Hz signal on my crappy desk speakers. Thanks! I learned several new things today.

Early pagers used tuned vibrating reeds to detect the pager message call tones. The pager receiver converted the signal to audio and used this to drive the tone detector coil that stimulated the resonant reeds.

Thanks for the fascinating videos this year!

Thank you for the updated video very satisfying watching it changes frequency. Keep up the good work

it somehow works like a blade-harp. The same concept for working and producing sound by resonance is also valid for mouth-blown harmonica instruments. Not by alternating current flowing through a electromagnetic coil, making the blades resonate to the frequency of each individual blade (spring steel), but by airflow. You blow air into with your mouth, and when a key is pressed, a sound is produced by a blade resonating in the airflow. Same also is working in a the folding harmoniums - pull apart and together all the time while playing - (traditional instruments, also the smaller 6-edge or round tango-harmoniums work this way) And also crank-driven music-clocks have such a tiny "bladeharp". Add: Please don't compare "DC resistance" with "AC resistance" across an AC power transformer or even across every other type of transformer !!! it has much higher "effective resistance" for AC (also increasing with increasing frequency, so it varies according to how it is used) actually. so your powerstation won't "cook" itself up with sending AC through it. DC resistance is low of course (because no self-inductive effects going on, except for the moment it is being switched on, it "retards" the inrush impulse because of the self-induction, but thereafter the DC resistance is what remains. Totally different when in AC use. AC across a coil produces additional inductive resistance because of the ongoing selfinduction effect steadily (changing currents and voltage levels all the time) AND current and voltage peaks are getting shifted apart by the phase shift caused by induction effects, varying the momentary resistance according to where the wave ascent/descent is currently, and which "time-constant" is valid for the indivudual transformer, its inductivity and how tight its coupling is, depending on a certain frequency (it varies with the frequency).

This thing is so cool, it kinda felt like it's experimental potential hadn't been explored in the previous video. In short, "I wanna see more!" Man watching the frequency shift along the dial is super cool!

Thanks for the follow-up! Was fun seeing it used as a pickup :)

Well done! That was really cool to see.

I first saw one of these devices recently as an RPM meter that was intended to be bolted onto a piece of equipment. If you were to mechanically couple that thing to the speaker cabinet, or maybe to a motor with an eccentric weight you could get it to behave exactly the same way as if excited through the coil. And yes seeing one of these things without any electronics present really was a bit of a head-scratcher at first for us too.

Thanks for going the extra mile and showing us the meter on several frequencies... :)

Awww, yisss! I was happy with the first video, but seeing that meter do its thing has made my evening. Thanks Fran! Thanks Patrons!

The length of the resonator "fingers" might give a hint to why the two plates are angled. On the higher frequencies, the fingers are shorter and therefore relatively stiffer, so they need a little more force to be actuated. The closer the plate, the more effective its magnetic influence gets.

dc resistance is different than ac resistance when measuring transformers or voice coils. A single ended tube amp can drive that meter directly before the output transformer.(add dc blocking cap) i have 3 different output transformers currently on my bench with ac measurements of 6500ohm to 8. at the start of the video i was going to suggest using a audio line output trans. or a 70 /100 volt speaker trans. as they would be a close match. but the speaker to line one worked well also. maybe someday ill get into video ,but repairing vintage tube amplifiers is really my passion. i love to see females in a male dominated industry. keep up the good work!

It's missing a critical part of a pickup, the magnet, so the signal is really weak as it relies on what ever magnetism is on the tines themselves. But obviously there's still enough current for the amp to pick up.

The "Do not open" and "Sealed" warnings (and variations) are common on old test equipment in order to discourage users from "fixing" them. As you know, these meters have very delicate internal components that are easy to damage. I had to learn this the hard way while trying to learn how to fix them. I "fixed" more than my fair share! Some meters, Weston 260s and old Thomson ammeters for example, even have some kind of resin covering the screw you need to remove to open up the device.

Your vids always make me smile and bring enjoyment to my life. Stay safe out there Fran! 💙

I dragged an old military generator out of my barn that I haven't used for years and there was one of these "meters" on the panel. Mine has the 60 in the middle, but same brand. They were very common.

You can easily drive a transformer like that with an amp. The amp doesn't 'see' the DC resistance. It sees the inductance of the transformer, which is MUCH higher than the 4-8 ohms of a speaker @60Hz. Try it, and put an amp-meter in between.

The plates either side of the tines form the reactive elements to impose physical motion to the tines themselves. If they are simply magnetised they wouldn't have anything to push/pull against. The taper would be a tuned transition to linearize the amount of motion across the frequency range for a given voltage, the lower frequencies being more efficient afford more gap, the higher frequencies need more energy to be conveyed so the gap is progressively smaller. Great video again Fran, thanks for your efforts.

that was a pretty cool experiment, and i'm sure the ones that made the trolly comments had no idea what impedance mismatch was, let alone that impedance is resistance to current flow in AC waveforms, thanks for the vid Fran, and keep being awesome

The slightly odd thing about this meter for me, is the range is so large (56 - 74 Hz) and not symmetrical about either 50 or 60 Hz compared to others I have seen that cover, say, 48 - 52 Hz. Questions and more questions Fran ! You played it like a musical instrument anyway, hopefully that will satisfy those who couldn't imagine that in their heads :o)

You mean that multimeter is measuring impedance at 60 Hz, not DC resistance?