help pls...measuring AC frequency

This may be way too easy for you folks, but it would sure help me if someone could answer.

I have a generator at an off-grid cabin hooked to a charger/inverter system with 4 golf cart batteries. Works great to get 110v 24x7 only running the generator ~2 hours daily.

Recently I upgraded my charger to a unit that has tighter power quality tolerances.....specifically, it requires input AC voltage to be within 5v of

120v and frequency to be within 5Hz of 60Hz. The diagnostic on the charger is telling me my generator has "bad AC" and is putting out 67Hz.

I have the generator at home now and want to measure frequency with my multimeter....it is a Radio Shack 22-812. Bear with me now please, because I don't understand electricity and electronics all that well. The user instruction manual is very cryptic but I think that I set the main control on one of the V (voltage) settings, probe the 110v outlet with red on hot and black on neutral (not on ground, right?), and then after I get the voltage reading, I press the Hz/Duty/Width button to cycle thru the various settings, specifically here to get the frequency from the Hz option.

Does this seem right? There is also another option on the main (round) control that says Logic/Hz, but I am reading an ambiguous comment in another place in the manual that that setting should not be used for any circuit with significant voltage (maybe that option is for getting frequencies say off of an audio signal, or ?).

I have searched all over the internet to try to understand how to make this measurement, but I ham having problems figuring it out. Can someone help?

Also, on the main control, for the voltage options, there are two given. One says 1) dBm~V, while the other says 2) C/F_V, where in the latter, the _ is a flat bar with three dashes below. One place in the manual says these options mean 1) "selects AC voltage measurement in dBm or volts", and 2) displays temperature and measures DC volts. It seems quite obvious that if I want to measure AC frequency I should select option 1), but in the part of the manual that advises the procedure for "measuring AC voltage frequency", the intro says "The meter can measure the frequency of an AC voltage, with or without a DC source bias", and then in the first subpoint it says "If you are measuring AC voltage with a DC source bias, set the function selector to dBm~V. Otherwise, set the function selector to C/F_V". (it then proceeds to advise to press the Hz/Duty/Width button, etc). This seems backwards to me, like a typo. I don't really know what "DC source bias" means, but I think 110v power from my gene or from my outlets in my home should not be "DC source bias". IE, I SHOULD use the dBm~V function, right?

I hope someone here can help me so I don't blow up my new $70 multimeter.

Thanks,

Tim

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news-server.mn.rr.com
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"news-server.mn.rr.com"

** Just connect a 120 volt electric clock/clock radio ( digital or normal ) to the gene.

Time keeping will only be good if the gene is spot on 60 Hz.

........ Phil

Reply to
Phil Allison

If only that were true. Clock radios regard power sources as power sources. A digital clock will take a dirty AC source and convert it to a nice, clean DC signal.

To the OP:

The comment about Logic/Hz must be heeded. That is for logic circuits, nominally for 5V. If you pick a voltage too high, depending on the meter, there is strong chance that you will fry the fuse inside.

The dBm normally means decibels-over-milliwatt. Not sure what it means in your context.

The DC bias feature is for signals that are sine waves whose average value is not zero, is normally the case. So you might have a signal that is a sign wave with +5V--5V peak-to-peak, riding on a DC voltage of 50V, so that when you look at it on oscilloscope, the combined voltage still looks like a sine wave, but never rises above 55V, and never drops below 45V. The DC bias switch is a way of telling the meter to ignore the DC offset - what you're really interested in is the AC wave. As you guessed, your generator has a zero DC-biased (normal, no frills sine wave). The C is for Celsius (as you probably guessed after writing post) and F is for Fahrenheit.

Not sure what kind of generator you have, but many of them allow you access to the governor (speed control). Tweaking it a little bit would slow the engine down a few cycles to get you within range of 60Hz. [Not sure why they don't simply build an electronic feedback system to keep the generator at 60Hz.]

-Le Chaud Lapin-

Reply to
Le Chaud Lapin

"Le Shithead LAIR "

** Shame how it IS true - you f****ng TENTH wit.

** ABSOLUTE BOLLOCKS !!!!!!!!!!!!!!

Go look up how typical clock radio ICs operate.

A sample of the AC supply voltage is fed to the clock chip for timing purposes - if and when the AC supply fails, a simple ( not very accurate) RC oscillator takes over until the AC supply is restored.

Normal AC clocks use a synchronous motor.

Wanna doubt that too - asshole ??

....... Phil

Reply to
Phil Allison

Well Well Well.

Yesteryear clocks did often use the AC line frequency as the timing source for the clock. In fact some chips even had a 50/60 Hz select input so that the chips were useful in more parts of the world.

Today there are many more clock designs that use an IC chip connected to a 32.768 KHz crystal. These designs often have both a backup battery and get power from the AC line. However it is often also the case that it is cheaper to produce products that use just batteries if the product only offers a clock function.

- mkaras

Reply to
mkaras

"mkaras" = s*****ad #2

** Fuck Fuck Fuck OFF IMBECILE .

** BOLLOCKS - there is no " yesteryear " about it.

The AC supply is still ** by far ** the most accurate timing reference at low cost for a mains powered clock.

** Go NOTHING to do with the vast majority of AC powered clocks & clock radios.

F U C K W I T !!!!

....... Phil

Reply to
Phil Allison

That's odd; I've built several clocks based off the AC mains and they are still accurate TO THE SECOND months later, using NIST as a reference.

Reply to
hondgm

Yes, my error. You're both right, you and Phil. ;)

-Le Lukewarm Lapin-

Reply to
Le Chaud Lapin

Gad, Tim, I don't know what happened to answering your fairly straightforward question.

Nice of Radio Shack to put the manual online as a PDF. Measuring frequency is covered on Page 25-26. It's the section starting in the middle of Page 26 that you want to follow. DO NOT use the "Logic/Hz" setting of the function switch. That's for low voltages only. You actually should be fine with EITHER the dBm/~V or the C/F/-V setting. Since you probably already want to test the AC voltage, just pick the dBm/~V setting. After measuring the voltage, press the Hz/Duty/Width button until "Hz" appears (I assume on the right side of the display, but they don't show any display pix in the manual!). Connect the leads to the generator. It's not clear if the meter is capable of resolving less than one Hz; you may see 67Hz, or 67.3Hz, depending. I assume it can resolve down to 1Hz at least, though.

Looks like a pretty capable meter. Maybe it will be incentive for you to learn more about 'lectronics! It can be enjoyable, if you don't let the grouches get to you.

Cheers, Tom

news-server.mn.rr.com wrote:

Reply to
Tom Bruhns

Yup. I also concur with Tom Bruhns - don't let the boneheads get you down. Actually, this can be a pretty harsh NG, so I've gone ahead and crossposted this to s.e.basics, with followups to there; that's really where this question belongs, and the people who frequent there don't denigrate newcomers - they're very welcome, and it's a very helpful group. Some of the posters in s.e.design participate there as well, when they're sober. ;-P

Anyway, I've left the rest of the post for the benefit of s.e.basics:

Cheers! Rich

Reply to
Rich Grise

On Tue, 28 Nov 2006 21:42:14 +1100, "Phil Allison" Gave us:

He said digital, dumbshit.

Nearly ALL electrically powered "clocks" these days have the same precision crystal stepping them at 32,768, which is exactly 2 to the

15th power.

All that is then needed is 15 divide by two stages. All watches that are not 100% mechanical, and all battery operated or AC operated "digital" clocks use it as well.

Have you ever made a post where you aren't insulting someone?

That goes for the retarded topic header title changes as well. Did you ever mature beyond the mental age of twelve?

Reply to
JoeBloe

On Wed, 29 Nov 2006 00:15:26 +1100, "Phil Allison" Gave us:

You're an idiot. I can buy AC powered clocks at the dollar store that have quartz timebase circuits in them.

Reply to
JoeBloe

On Wed, 29 Nov 2006 00:15:26 +1100, "Phil Allison" Gave us:

"Go NOTHING"??? What the f*ck is that, retard boy? Is that you waving to us as you go?

Go, NOTHING, GO!

Most clocks today, even AC powered jobs have crystals in them. Maybe in your half assed backwards neck-o-tha' woods they don't, but 'round here they surely do. In fact, it is harder to find an AC powered wall clock out here. Most are single cell operated, QUARTZ timed, bob-o-loid designs where the second hand is toggled by a small, swinging bar that moves through a dual solenoid actuator. The quartz crystal times the pulses sent to the solenoids.

Reply to
JoeBloe

If you didn't reply to Phyllis we'd all be spared this nonsense ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

"Joe Bloe It Out His Arse "

** He was replying to MY use of that same word.

Do try to follow the thread - Mr Anonymous Fuckhead.

** Clocks are not the issue in point.

The actual comment was:

" a 120 volt electric clock/clock radio ( digital or normal ) "

** ABSOLUTE BOLLOCKS !!!

Go look up the data for the very popular TMS3450 NL or LM8560 " digital clock radio " ICs

No crystals in sight.

A 50 /60 Hz supply is as the reference.

Cos it is far more accurate than a watch crystal.

** I make a special effort to insult congenital liars and fools like YOU to the max.

Frankly, I would prefer to see you all hanged by the balls.

........ Phil

Reply to
Phil Allison

On Tue, 28 Nov 2006 18:59:09 -0700, Jim Thompson Gave us:

You're right!

You could have at least chimed in on the topic though.

Reply to
JoeBloe

"Joe Blows It Out His Arse Fuckhead "

** ROTFLMAO !!

Damn shame how the AC supply frequency is far more accurate than a watch crystal.

Now FUCK OFF you know nothing pile of SHIT !!!

...... Phil

Reply to
Phil Allison

Some things are so juvenile as to not be worth commenting ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

you may want to check the datasheet of the sanyo LM8560, this common LED clock chip uses the AC supply for its clock source, and an RC oscilator only when the mains fails.

given an off-frequency (or noisy) supply it will not keep good time. given a good AC supply these clocks keep excellent time.

Bye. Jasen

Reply to
jasen

JoeBloe wrote: On Wed, 29 Nov 2006 00:15:26 +1100, "Phil Allison" > Gave us: >

Sorry, Allison wins on this one. The AC line frequency IS by far more acccurate than the crystals in cheap clocks. Line counting digital clocks or synchronous motor mechanical clocks are dead on all the time. You haven't noticed those cheapies always need to be reset?

GG

Reply to
Glenn Gundlach

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