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  #1   IP: 204.191.140.101
Old September 15th, 2010, 08:11 PM
cb250rs cb250rs is offline
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Default Cheap frequency tester

Hi,
Thanks in advance for direction and help.
Does anybody know of a cheap frequency tester, or a cheap way of testing the frequency. I guess the fluke testers are good, but they are not cheap.

This will sound crazy, but I thought of testing the frequency with an old 33rpm record player.
I figured I'd see how many revolutions it would make (in say 3mins)hooked up to the grid,and then compare it to my generator output. I'd have an idea if my generators output was on the high, or low side and adjust the rpm accordingly.
It would be a lot easier though if I could find a cheap (but relatively good tester) out there.
This is a hobby for me so I don't really want to spend a ton of money if I don't have to.

Anybody got any ideas?

thx
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  #2   IP: 66.122.185.191
Old September 15th, 2010, 08:41 PM
wannabe wannabe is offline
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well, im confused as to your relational idea between a phonograph and a generator.

But, the output of a bobbin style generator is based on engine rpm.

most generators have a "NO-LOAD" rpm somewhere between 3650-3750 rpm. The reason for this is the LOAD reduces the rpm slightly down to 3600 rpm and brings the cycles per second close to 60. I dont remember the math and the maunals I need for the numbers are at work.

The newer more efficient cyclo-converter generators are not dependant on engine rpm for output as they take ac power and convert it do dc and then back to ac making a perfect 60Hz square wave 120 VAC output.
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  #3   IP: 207.35.6.2
Old September 16th, 2010, 06:28 AM
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joed joed is online now
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Plug in an electric clock?
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  #4   IP: 76.203.32.116
Old September 16th, 2010, 09:22 AM
dznewz dznewz is offline
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Measure the engine RPM with a tach. Unless, of course, the generator you refer to isn't an engine driven AC generator.
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  #5   IP: 204.191.140.101
Old September 16th, 2010, 06:03 PM
cb250rs cb250rs is offline
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Yeah........ I don't have a tachometer either. I think I understand the relationship between revolutions and frequency.

1 hz is one cycle a second therefore 3600rpm will give me 60hz.

So heres my question, how can I determine if the frequency or RPM are accurate. without spending a ton of moey on a tachometer or fluke multi meter.

OR Could anyone recomend a multi meter to me that is reasnobly priced - thanks
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  #6   IP: 72.38.193.87
Old September 16th, 2010, 06:54 PM
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RPM depends on the number of poles on the generator. Diesels at the office run 1800 RPM.
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  #7   IP: 204.191.140.101
Old September 18th, 2010, 02:35 PM
cb250rs cb250rs is offline
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Default Thanks JOED

I have an uncle in the electricity generation and distribution business - he knows his stuff - I think you do too.
An old electric clock will work just fine.
I can still use it for comparison to the grid if it isn't accurate, but if it is accurate then:

If a minute on the clock comes faster than a real minute, then I need to slow generator down. If a minute doesn't come as fast as a real minute, then I need to speed the generator up.

If I am accurate to one second then I am accurate to 1hz (which I think is around 1.6%)

Thanks JOED, now how can I make a cheap Meggar tester?
I'm not too concerned about this as they seem to be reasnobly priced.
thanks again

Last edited by cb250rs : September 18th, 2010 at 02:44 PM.
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