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davenn
Moderator
You need much more than just a meter to determine frequency
How about googling " circuits for analog frequency meters" and see what you find
The meter you have may be marked in Hz, but that doesn't mean it directly measures frequency (e.g. consider a meter with a scale of litres/minute - you wouldn't pour water into it)
An analog frequency meter is often driven by a circuit that converts a frequency to a voltage. One way of doing this is to convert the incoming signal into a pulse train of the same frequency, but with fixed length pulses. The average voltage of this equates to the frequency.
An analog frequency meter is often driven by a circuit that converts a frequency to a voltage. One way of doing this is to convert the incoming signal into a pulse train of the same frequency, but with fixed length pulses. The average voltage of this equates to the frequency.
This meter is very old certainly before transistor and it does read the Hz with the reading roughly in the centered of the vibrating needle. I was just wondering what type of circuit would calm it down.
Could this kind of meter not work on sine waves or an amplitude issue.
Thanks for your reply....colum
Could this kind of meter not work on sine waves or an amplitude issue.
Thanks for your reply....colum
When you say "meter", do you mean a simple meter display or something that has active components, transistors or values?
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One way is to generate a fixed length pulse per cycle of the input and then to average thw DC level. Again, needs active components.
This is the reason I asked for an image or description.
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If you have just the moving needle display part, then it will read current, or maybe voltage; you'll need some circuitry attached that turns frequency into current of voltage.
Got a picture?
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What people were saying above is that there is no simple way to read frequency with just a moving needle meter without something active to count cycles, or to average pulses or similar.
One way is to generate a fixed length pulse per cycle of the input and then to average thw DC level. Again, needs active components.
This is the reason I asked for an image or description.
.
If you have just the moving needle display part, then it will read current, or maybe voltage; you'll need some circuitry attached that turns frequency into current of voltage.
Got a picture?
Thanks Nanren888. I see what you mean about the input conditioning. As a hobby during the pandemic I 'm fixing old old power supplies and the input for the " tuned coil " vibration meters need amplification adjustments to read correctly but are Ok with sine waves.. the needle meters are much tougher apparently...Jeff
bertus
Moderator
Hello,
An other type of analog frequency meter is the vibration type:
https://www.google.com/search?q=vib...ent=img&ei=7uWVX9jSG5KmkgWGrIzQCQ&safe=images
Can you show a picture of your meter?
Bertus
An other type of analog frequency meter is the vibration type:
https://www.google.com/search?q=vib...ent=img&ei=7uWVX9jSG5KmkgWGrIzQCQ&safe=images
Can you show a picture of your meter?
Bertus
Hi bertus. Sorry my camera is busted..I have round faces that are either 60 cy + - and 400 cy + -
and a load of vibration meters that are placed on motors that record the rotations of many speeds and one that is hand held that shows 1750 rpm + - all with no electric contact..I've spent too much time at flea mkts....Jeff
and a load of vibration meters that are placed on motors that record the rotations of many speeds and one that is hand held that shows 1750 rpm + - all with no electric contact..I've spent too much time at flea mkts....Jeff
davenn
Moderator
You dont have a phone camera ?
hevans1944
Hop - AC8NS
@colum: Jeff, does your location of Midhudson mean Mid-Hudson, this area of New York State? Is your avatar a photo from a model railroad, HO gauge perhaps? Just curious.
BTW, I like the old resonant vane frequency meters, but modern electronics makes it pretty easy to get a wider frequency range and better accuracy... unless your interest is just in the antiques.
Back in the day (1950s and 1960s) electronic tachometers driven from the breaker points in the ignition system were all the rage in hobby magazines. I always drove vehicles with automatic transmissions (until I began driving motorcycles), so I never needed a tachometer. Nevertheless, my first "real" car was a 1968 Mercury Cougar with an automatic transmission and... you guessed it... a tachometer. Go figure. This car also had "way cool" sequential rear turn signals. Unfortunately the implementation was electro-mechanical (motor-driven switches actuated with cams), so eventually it failed and the cost to replace it was prohibitive.
BTW, I like the old resonant vane frequency meters, but modern electronics makes it pretty easy to get a wider frequency range and better accuracy... unless your interest is just in the antiques.
Back in the day (1950s and 1960s) electronic tachometers driven from the breaker points in the ignition system were all the rage in hobby magazines. I always drove vehicles with automatic transmissions (until I began driving motorcycles), so I never needed a tachometer. Nevertheless, my first "real" car was a 1968 Mercury Cougar with an automatic transmission and... you guessed it... a tachometer. Go figure. This car also had "way cool" sequential rear turn signals. Unfortunately the implementation was electro-mechanical (motor-driven switches actuated with cams), so eventually it failed and the cost to replace it was prohibitive.
Have a look at the link below. It takes you to a datasheet for the LM331. The LM331 is a Voltage to Frequency / Frequency to Voltage converter.
There is much info on the datasheet including application notes.
https://www.ti.com/lit/ds/symlink/l...l-digikeymode-df-pf-null-wwe&ts=1603698036207
There is much info on the datasheet including application notes.
https://www.ti.com/lit/ds/symlink/l...l-digikeymode-df-pf-null-wwe&ts=1603698036207
Thanks Hevans 1044 for your interesting history. I live in sight of the old RR bridge in Poughkeepsie NY and was in use up to the 1970s but caught fire and was abandoned until 2005 or so then it has became a very long walkway over the Hudson river
from Pok to Highland. I don't know much about trains but Im really fascinated by them. I did travel from London to Hollyhead England in a steam train a long time ago
My interest in these meters are trying to resurrect old power supplies in particular the tuned coil that can register the speed of the rotor by just contact with the housing ( try that electronics ) and they are accurate too but probably only AC motors
Be well...Jeff
from Pok to Highland. I don't know much about trains but Im really fascinated by them. I did travel from London to Hollyhead England in a steam train a long time ago
My interest in these meters are trying to resurrect old power supplies in particular the tuned coil that can register the speed of the rotor by just contact with the housing ( try that electronics ) and they are accurate too but probably only AC motors
Be well...Jeff
hevans1944
Hop - AC8NS
Pretty spiffy IC you linked to, @WHONOES, although the spec sheet does say the frequency-to-voltage conversion (in which the OP is interested) takes longer than the voltage-to-frequency conversions, but the accuracy is impressive either way. Something "new-to-me" I should learn to play with.
@colum: I am not familiar with "the tuned coil" method of rpm measurement. Is it based on some sort of mechanical resonance, perhaps measuring minute vibrations given off by a slightly unbalanced rotor of the motor whose speed you want to measure? If that is true, then the "rpm meters" should work with AC as well as DC motors, since the vibrations are solely a mechanical phenomenon. OTOH, motor manufacturing has been pretty much a done deal since the beginning of the twentieth century, with a lot a attention paid to bearing design and reduction of rotating losses. That's why you can buy drone aircraft electric motors with speeds upwards of ten thousand rpm today. And I can remember when air-powered, water-cooled, turbines used in dental drills became all the rage, eventually completely replacing belt-and-pulley electric-motor-driven dental drills.
@colum: I am not familiar with "the tuned coil" method of rpm measurement. Is it based on some sort of mechanical resonance, perhaps measuring minute vibrations given off by a slightly unbalanced rotor of the motor whose speed you want to measure? If that is true, then the "rpm meters" should work with AC as well as DC motors, since the vibrations are solely a mechanical phenomenon. OTOH, motor manufacturing has been pretty much a done deal since the beginning of the twentieth century, with a lot a attention paid to bearing design and reduction of rotating losses. That's why you can buy drone aircraft electric motors with speeds upwards of ten thousand rpm today. And I can remember when air-powered, water-cooled, turbines used in dental drills became all the rage, eventually completely replacing belt-and-pulley electric-motor-driven dental drills.
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