Vibrating reed frequency meter
100 Comments


So today let’s take a look at this
amazing frequency meter as I promised in the last video. It’s a vibrating reed
frequency meter. It has some metal strips in it with some resonance frequency and
those are resonating and showing the frequency. There are multiple strips and
each of them has a different resonant frequency according to this scale and
the one with the same frequency as the input voltage on those terminals will
resonate and show the frequency on this scale basically and there are
basically some flexible metal strips and one end of it is connected to some
support and the other end of it is free and it can resonate and those ends are
those you can see the free end of it which is vibrating and they’re different
frequency which can be achieved by different length or also by a different
weight on the end of it basically. It can be calibrated using a different size of
a blob of solder which can be removed or added for calibration. The heavier the
lower the frequency and the longer the lower the frequency. So it can be for
example like this and there is also a coil next to it connected to those
terminals and according to the frequency of the voltage one of those strips will
resonate. And here you can see the front of the resonating reed and when it’s
resonating up and down it looks longer. In operation it looks like this. For
example when it’s 50 Hertz it looks like this and if the frequency is in between
of two you can see something like this. So this is actually somewhere here which
means 49.75 Hz. Those reeds are 0.5 Hertz apart, but when two of
them are resonating it means it’s in the middle so you can read it with about
0.25 Hz resolution. This coil with an AC current in it is producing a
vibrating magnetic field but it makes the reed resonate only if the
mechanical resonance frequency of the reed is very close to the frequency of
the current in the coil. So only one of them or maybe two are vibrating and the
other ones are not. But those reeds are probably just iron, not a magnet, so they are attracted to the coil in both half cycles, so the
resonance frequency is probably double of the frequency in the coil. This is the
current in the coil and the magnetic force is basically square of the current
in the coil. The same is happening for example in universal motors or in analog
meters which measure RMS current. But now let’s take a look at it. It measures
frequency from 48 Hertz to 52 Hertz. It’s rated for 127 Volts ac and it’s made
in Soviet Union in 1962. The resolution of it is not very good and also the
range of it is very narrow, but it’s quite an amazing device nevertheless and
it was apparently designed to measure the mains frequency. But nowadays the
frequency of mains is controlled with quite a high accuracy like 0.01 Hertz, so
this device would be absolutely useless to measure the deviation of the mains
frequency nowadays. maybe it was used to measure the frequency of a generator which
is not connected to mains (an offline generator) or maybe it was measuring the
frequency of a generator before connecting it to the mains. Or maybe the
mains frequency was quite inaccurate back then. Maybe in 1960s in Soviet Union
the frequency was fluctuating like crazy. And it’s designed for 127 volts. And the
mains in Soviet Union probably was like this. It was a three phase mains and the
transformer was like this: the voltage from one phase to the centerpoint was
127 volts and the voltage from one phase to another was 220 volts.
Tell me if I’m wrong, but I guess that the transformer from the high voltage to
the low voltage for customers was like this, so you could have appliances for
127 volts or 220 volts. But now of course you probably want to see it actually
running. So let’s test it. It has a coil in it (probably) so it
should have some resistance. Well, it doesn’t work. It can’t measure the
resistance of the coil, so it seems like there is something wrong. There’s time
to take a look in it. There are three screws for a flat screwdriver because
almost all Soviet devices have flat screwdriver screws in them. So let’s
open it. And my cat is going to help me of course, as usually. Can I open it like
this? Yes. So here you can see the metal strips – the reeds with quite a lot of
screws holding them and from the other side there’s the electromagnet with this
coil mounted on some core. Basically this coil is producing a magnetic field
and it goes from here into those bars attracting those reeds and of course the
magnetic field has to make a full circle from the coil through those reeds
through this or this back into the coil. And here you can see the terminals of
the coil going from here into those screws. And here you can also see the weights
it’s on the reeds which are probably blobs of solder so it was probably
calibrated by adding or removing some solder. So those are probably solder
weights. And this is the tail of my cat. But unfortunately this coil looks rather
dark. It looks like it overheated. I’m not sure if it’s supposed to be this
dark, almost black, but because it’s open a circuit it’s probably gone. And I have
a feeling that somebody connected a wrong voltage to it because in my country
and in the entire Europe the voltage is 230 volts and this one is for 127 volts.
Somebody probably tested it using European mains voltage and destroyed it.
but sometimes windings fail for no external reason. They just develop a
short turn – a short circuit between the turns of the winding and then they
overheat, the wire melts and they go open circuit. So let’s try to disassemble
it. There are three screws holding the core together. Can I open it? Does it come apart now? So here’s the
coil which unfortunately is open circuit. So let’s take it out. Let’s see the winding
in it. It doesn’t look bad. It’s not burnt. That’s weird. But maybe
this is the normal color of the isolation. The wire doesn’t look burnt. There is some glue on it but the wire seems ok.
but why it’s open circuit? Maybe somebody dropped it and the wire broke. I don’t
know. So I probably have to unwind it to see what happened.
Maybe it’s burned somewhere in the center of it. So here’s the winding
which doesn’t look burnt. It probably broke because somebody dropped it,
because it went through a post. And there is definitely quite a lot of turns
in it. So this is what I call a non-countable winding.
It was just impossible to count the turns, so I just cut it,
I took detailed pictures of it and it seems to be over 10,000 turns. It’s
impossible to count it and from the pictures it seems like there is about
220 turns in each layer and there is about 50 layers. And this is about 11,000
turns … per 127 volts and this is … about 87 turns per volt. So now let’s try to
rewind it because the spool is okay. Here you can see the options. The first option
is to rewind it for the European voltage. But this means about 20,000 turns which
is completely crazy. Of course you can do it using a drill or something but at
this high voltage there is also a risk of a failure.
I could also rewind it to the original voltage but this is a completely useless
voltage for me because the mains is different here. And the last option is to
rewind it for some standard low voltage like 6 or 12 volts. It would be 520 turns
for 6V or 1040 turns for 12V. I will probably do it for 12V.
I have to get some proper wire for it, but now let’s do just a very temporary
test using a random cable. And this is really just temporary. It has to be done
using a proper wire for windings, of course.
OK, so let’s test it. So let’s test it using a transformer. And it seems to do
something! it’s a bit off, but OK, it works. It shows about 50.25 Hz. And of course I can’t run it for long
because this wire is going to melt. The wire has a rubber isolation which can
easily melt and it also fills most of the space in it so there is not much
copper. And this is another reason why it’s going to melt easily. Now I can’t
run it for long. I have to rewind it properly. Now let’s measure the current.
3.6A, that’s quite a lot. And the voltage is 2.2V
and there is 50 turns in it, but of course the voltage
per turn has to be higher now because the rubber fills most of the space and
there is not much copper, so it has a high resistance and it drops more
voltage. So this is DiodeGoneWild and see you in my next videos. And thanks to all of
my patrons on Patreon! I really appreciate your support! and of course in the next video I have
to rewind it properly and test it using a variable frequency.

100 thoughts on “Vibrating reed frequency meter

  1. You don't need to rewind it as original. I run low turn coils like this with a capacitor in series (4,7uF) and it wooooorks … amaziiing 😉 The current is about 0.3A and the strength of the magnetic field is good enough, while consuming reactive power. It's probably even better than the original.

  2. These types of meters fascinate me, all they are is a wobbling strip of metal, but due to resonance frequencies and calibrated weights, they make accurate measurements of frequencies… 🙂

    Only have one example of such a meter myself and that's built into my Honda EX650 generator to measure between 50Hz and 60Hz depending which mode it's set to…

  3. Yea those doohickies are perty neat. I have a mhz 1-25 which i have no clue what would use that frequency really it used to live on a factory belt line motor on a vfd. Ihad to upgrade it because being its working principle of vibration it was a hairy bitch having to read when a hopper down the line was having a seizure and everyoneof those damn fingers were jigglatin. So after having to use my handheld needless to sayit came out and about went hulk smash mode on it but didnt because it was old it served its purpose. Reminds me of the wind up musicbox era.

  4. The hand written date on the dial is actually December of 1968. Such a frequency meter is something I have very rarely seen and I never owned one so far, despite of my crazy hoard of random stuff including even pacemakers and missiles seekers.

  5. Using a signal generator and audio amplifier you can now play across all measuring instrument range as I did in my youth age.

  6. It is very possible, that the mains-Frequency was very unstable in the soviet union, back in the day. My Grandfather was once there and they build a gigantic water-heater out of many small water-heaters. When they plugged it in, the lights startet to flicker, and the power lines of the town startet melting!

  7. Looks like a cross between some el-guitar guts, a voltmeter, and a harmonica.
    In other words, Half voltmeter half el-guitar innards and half harmonica.

  8. Could you use it to measure other frequencies, since the metal strips probably has more than one resonant frequency, if you have a frequency generator to test it , it would be awesome. I like your explanation of working principle for most videos you got.

  9. What a beauty. Ask an EE to do this today, and all you will get is a costly PCB with a zillion different chips on it and a power hungry display.

  10. СССР мы Россия мы свет электроный 50 Hz как же не нужем мы говорить Русский язык только и что то ламойный украл жашном?

  11. My grandpa's DIY car battery charger had the same meter but an 230v. I still use this to charge my cars but I removed the frequency meters since it wasted too much voltage. I have to look at the charger when I drive to and if I get it out of the charger and I would then message you to get your address or P.O. Box details

  12. This old technology was simplistic and extremely accurate. Long ago I was given a basket-case 14KW military generator that was complete. It had a 4 cylinder Continental engine with a row of taps that could be connected from 110 to 440 volt single phase and 3 phase. I put new meters for Amps and Volts as an upgrade, but the frequency indicator was like this one with 60 HERTZ being red. There was a fine RPM knob on the dash where you could "dial in" the engine speed and the red would be the only one of the 9 vibrating. It was like new when I finished it and was vastly underrated. I sold it to a fellow who wouldn't be on the grid for a year and he ran his entire truck shop on it.

  13. You need a frequency measuring device in every power plant. If you power up a generator, before connecting it to the mains grid, it must be synchronous with the mains. Otherwise you'll have a short-circuit.
    That principle is very old. There are several methods how such frequency meters work, and several patents. For example method "Hartmann-Kempf", the book is from 1927:

    https://books.google.de/books?id=kHaLBwAAQBAJ&printsec=frontcover&hl=de#v=onepage&q=hartmann-kempf&f=false

    I agree, it was my first thought too: 127V fits into a three-phase system. Every phase 127V against neutral or ground. Phases against each other 220V.

  14. Maybe rewind it for 12V, it would be much easier than trying to wind thousands of turns of fine wire so neatly. Then you can use an external transformer which are very common for old halogen lights at 12V.

  15. I regularly watch your videos not only because they are well done and really interesting, but because I looooove your accent 🙂

  16. I saw this type of frequecy meter a lot in old panels. When a very big (and I mean BIG as in hundreds of KW) consumer was turned on the mains frequency used to decrease. It was due to the cos(phi) alias inductive load. Then, a automated system (or a man) switched banks of capacitors to balance the inductive factor. This made the frequency to came back to normal. On those panels were also a cos(ph) meter, watt, var, volt and ampere meters and these were at the power entrance of the factory. Also this was used at the backup generators also to trim the speed with the load.
    Edit: I don´t know about USSR mains voltage, but I had some devices that all had the 220/127V switch, made in USSR. It seems that in the vast majority (or at least european side), the mains was standard 220V but in some republics were 127V.
    Also, this is not a so old device, these types were produced and used until early 90`s in communist countries. Then they switched to digital ones when the microcontrollers and microprocessors became widely (and cheap) avaiable. It seems that they are actually used and fabricated today, see http://www.aelindia.com/index.php/vibrating-reed-frequency-meter/

  17. Great you got the meter going again. even it was at relative high current but the meter works. Try to get some enamelled wire and rewire the meter for 12 Volts with a small TX to run it from the 230 V mains.

  18. I believe that your frequency is as stable as here in Finland where it now is 49,952 Hz. It would be an interesting project to calibrate that. I believe that the easiest way to fix the windings is to tahe a small transformer and use only the windings.

  19. When SU was getting ready to win the nuclear WWIII, we used to use this kind of frequency gauges on our military mobile power generators run on petrol. They were so poorly built as there was no any engine governor implemented to a throttle body so this gauge was the last resort to maintain proper output of the generator when manually opening/closing a butterfly valve on a carburettor.

  20. Great video I wondered how those meters worked. You are spot on with how the 127/220 volt mains works I think Norway still has that system in use but I'm not sure ( Never been there and not likely to go) also I believe France allso used to have a similar system in places even in London some places had a bi_phase system ie 110 0 110 with a center taped tranny all long gone now. The USSR and now Russian frequency is unstable its part of the reason why Russia isn't connected to the European grid although I think politics has a lot to do with it too

  21. Please make a video explain how did you do your watt meter (srry if something is write wrong im not very well with english, but i like your videos)

  22. Soviet union had 220v single phase and 380v between two phases. 127v was probably used in power plants and automatics for the plant.

  23. I believe they controlled model aeroplanes using Vibrating reeds
    https://en.wikipedia.org/wiki/Reed_receiver
    https://books.google.co.uk/books?id=Rud8CgAAQBAJ&pg=PT13&lpg=PT13&dq=controlled+model+aeroplanes+using+Vibrating+reeds&source=bl&ots=5Zd9lsEK4c&sig=rtPrkTSkGJ5ZxTF65OsdQYQqT5g&hl=en&sa=X&ved=2ahUKEwixwIjagPDfAhUHUxUIHe96CX0Q6AEwB3oECAgQAQ#v=onepage&q=controlled%20model%20aeroplanes%20using%20Vibrating%20reeds&f=false

  24. I seen exactly the same one instaled in old soviet army power generator some time ago. After start, you have to adjust rpm of the gasoline engine and some resistors on main panel to match correct voltage and frequency. As I remember right, there were volt and ampere gauges also present.

  25. Just an idea:You could try winding it with about 8 turns of 1.5mm2 wire and connect it in series like an Ampere meter.

  26. This is usually part of a so-called " measuring group " , which is Standardised like ,> Whatever Nominal Volts to 100 V , and > X Amps to 1 , or 5 Amp current Trafo s ! ( Of course , they add some tolerance , to prevent the magnetic saturation in case of a " little" over voltage ) After that You have the Ratios , and feed the other "standardised " instruments ,like Watt , Amp , Volt , P.F. ( cos phi , sin phi), reactive/ apparent power meters .

  27. Thanks for the detailed review of the device. You have a device of 127 volts, I have the same analogue of 220 volts, sometimes I connect to the network to see what you said. Thanks again.

  28. 06:40 Товарищ, эта изоляция часто приобретает такой вид сама по себе, без значительного нагрева, просто из-за времени. Насколько мне известно, это бумага, пропитанная эпоксидной смолой или лаком. Надеюсь, эта информация не была государственным секретом…

  29. 50,25 Hz je podle mě spíše chyba přístroje / měření, primární regulace a podpůrné služby přenosové soustavy to většinou udrží v rozmezí 49,90 – 50,10 a když už to jde k 49,80 nebo 50,20, tak primární regulace už jede naplno a pak už z toho je celkem průser a platí se celkem ranec za regulační energii 😀 Krom webovek níže se občas mrknu na frekvenci přes měřák Voltcraft Energy Logger 4000

    Evropská přenosová soustava (Kontinentální Evropa): https://www.netzfrequenz.info/aktuelle-netzfrequenz-full
    NORDPOOL (Skandinávie a východní Dánsko): https://www.svk.se/en/national-grid/the-control-room/
    Velká Británie: http://www.dynamicdemand.co.uk/grid.htm

  30. frequency meters are obligatory in offshore/marine installations that have the ability to synchronize generators. The synchronizing is done normally automatically but there must be a way to do it manually – therefore voltage meters and synchronizing panel meters are also required by Class Rules

  31. "The frequency of mains is controlled to 0.01Hz" not in my country, primary frequency control has been abandoned in favor of a FCAS ("frequency control") market to poor results. https://www.aemo.com.au/-/media/Files/Electricity/NEM/Market_Notices_and_Events/Power_System_Incident_Reports/2018/Qld—SA-Separation-25-August-2018-Incident-Report.pdf

  32. 127volts strikes me as closer to the output of a potential transformer (say, driving an instrumentation pannel). Likely for use on a small to medium sized system (train, boat, or municipal scale).

  33. I have always wanted to make a variable frequency high voltage AC generator just to have on hand for testing things such as that meter. Nice video.

  34. You said that the frequency is very precisely regulated nowadays. What about the time a few years ago when Kosovo shut down all its power plants so the frequency dropped significantly in most of Europe? I don't remember by how much the frequency dropped, but after a few days, cheap clocks that depend on the line frequency (aka mains frequency) to measure time were off by several minutes.

  35. These meters are very common here in Argentina in the xx century. The power grid are very unstable in tension an frequency in the past.
    The color of the coil cover probably is electric isolating varnish cured in oven.

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