Vibrating reed frequency meter

Vibrating reed frequency meter

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Today let’s take a look at a vintage 1962 soviet era vibrating reed frequency meter. It’s an analog frequency meter based on multiple metal strips (reeds). Each of them has a slightly different mechanical resonant frequency. It also contains a coil connected to an AC current. The reed with a resonant frequency very close to the frequency of the current in the coil will vibrate. This will indicate the frequency on the scale. Those devices have a narrow range of measured frequencies. They are mostly used to measure the frequency of a 50Hz, 60Hz or 400Hz mains.

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35 thoughts on “Vibrating reed frequency meter”

  1. 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.

  2. 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.

  3. 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.

  4. 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

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

  6. 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.

  7. 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:

    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.

  8. 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.

  9. Why don't you add a resistor for current limiting. I saw one with 2 rating 220V and 440V and it had 2 resistor.

  10. 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

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

  12. 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.

  13. 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.

  14. 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.

  15. 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!

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

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