relays

John Larkin wrote:

He is a fellow (not me, perhaps RG?) who asked you a straight question which you refused to answer.

Evasion noted.

Feel free to answer Dr Polemic's question any time now...

I will quote it to make it easy for you to answer (or to duck...):

| |Quoting "Dr Polemic"... | |In another post you said, (cut and paste from the post): | | "But that water will come out forever, with no further effort exerted | on the valve. The longer you wait, the more output power, without | limit. The output power is the *integral* of the input power. | |If the output power is assumed constant, as you make clear (in a subsequent |post) you are doing, then no matter how long you wait, you *don't* get more |output power. | |Clearly, you should have said "The longer you wait, the more output *energy*". | |You are chastising other people about wrong use of engineering units, yet you |make that same mistake. And, in responding to somebody who pointed out that you |had said "power" when you should have said "energy", you didn't admit that you |had made a mistake. You just amplified your point using the correct term, never |admitting that you had made a mistake, to wit (again, relevant cut and paste |from your post): | | "The output energy is the (assume constant) output power integrated | over time." | |You could have tacitly admitted that you had made a mistake by prefacing this |last sentence with "I should have said...", but you didn't. There was no |admission of an error on your part. | |It is said "Larkin _never_ admits error.", and you reply, "Sure I do, but I have |to be wrong first." You used the wrong engineering unit in this case; will you |admit your error? |

Well? What is your answer?

Because relay contacts are usually rated in VA. "VA" does not specify AC. VA is the product of volts and amps. But whether the load is AC or DC isn't the issue; one could decide to define the relay power gain either way; just say so.

The don't put contact ratings on datasheets? You don't know how to multiply volts by amps to get watts?

Fine; multiply those.

Convert to watts! Or VA. Same thing here.

Nope.

VA is volts times amps.

And volts. Multiply to get VA. VA is the same as watts here, just the product of what voltage and what current the contacts are rated for.

Why are you making this difficult? It's absurdly simple. Coil power in, load power out, and the ratio is the relay's power gain.

The contact voltage rating is whatever is on the datasheet.

Tha maximum legal power gain of the relay is measured with the contacts switching all the voltage and all the current they are rated for.

The *actual* power gain might be less if you don't run the contacts at their max ratings. It's just like a power amp that's rated for some power gain; the actual gain could be less if it's lightly loaded. And gain spec has to have measurement conditions specified.

This is all simple, unless you want it to be complicated. If you are determined to confuse the concept of power gain until it's meaningless to you, go for it.

If you are trying to say that you can't define the power gain of a relay, I'll agree that you can't.

I don't type very well, and I don't check Usenet posts much for typing and spelling. That's no secret. But I do understand fractions and engineering units.

Plagiarist. Invent your own insults.

John

| |From: John Larkin |Newsgroups: sci.electronics.design |Subject: Re: relays |Date: Thu, 13 Nov 2008 08:34:58 -0800 |Message-ID: | |...a latching relay has infinite gain. | ... | |From: John Larkin |Newsgroups: sci.electronics.design |Subject: Re: relays |Date: Fri, 14 Nov 2008 08:45:23 -0800 |Message-ID: | |John Fields wrote: | |>[...]a latching relay doesn't have infinite gain[...] | |We use a cute little latching relay that will pull in in 500 usec, |using about 125 microjoules, just once. After it's pullec[sic] in, it |will easily dump 50 watts, which is 50 joules per second. Measured |over one second, its power gain is 400,000. Over one year, it's |1.3e13. There's no limit on the power gain if you're patient enough. |

Is not a joule a measure of energy, not power?

Is not "125 microjoules" a measure of energy, not power?

Did you not use microjoules and watts to define *power* gain?

I stand by my statement. You started this thread by measuring power in (micro)joules, as shown by a direct quote from your posts.

How bizarre. Average power is measured in watts. Energy is measured in joules. They are not at all the same thing. The multiplier used in averaging is dimensionless.

Here's a simple example that may help: a night light uses 7 watts when it's on. Over one hour, on for half the time, its average power consumption is 3.5 watts. The energy consumed in that hour is 12,600 joules.

Really, this stuff isn't all that hard.

John

I don't debate sock puppets. He's probably cheating on his boss, so won't post his real name. I'm on the boss's side

John

Probably so; it was poorly worded, given the number of critters trying to bite at my ankles. It's the power *gain* that's the integral of time. You get power forever for a one-time control input.

Of course, I did make it clear, in any number of other posts.

you

never

Well, that's right, isn't it?

have

Get a life.

John

The numbers are correct. The averaged power gain and the energy gain are obviously the same thing, exactly the same dimensionless number. I just use whatever units are easier to get the answer.

John

OK. I am asking the same question, I post my real name, and I am the boss. Any other reasons why you won't answer?

Evasion noted.

There's no "probably" about it; you used the wrong engineering unit. You complain about others using engineering units, as in (cut and pasted from another post of yours):

"I seem to be arguing abstract math definitions with people who can't do simple arithmetic, or get their engineering units right."

It wasn't just poorly worded; it was a mistaken use of an engineering unit.

I'm sure you know the difference between power and energy, but you did in fact use the wrong term in your post. You made a mistake, and you refuse to admit it.

Anybody can make a mistake. I see any number of mistakes and misstatements by various people in this silly thread.

You, along with everybody else can be forgiven for making a mistake. But when somebody said "Larkin _never_ admits error.", you said ""Sure I do, but I have to be wrong first." You claim to be willing to admit a mistake if you make one. I've shown a mistake you made, and it's not just "probably" a mistake; it's a flat out mistake, and you refuse to admit it.

you

never

have

you

In their linear region, yes.

Sure, things like the fine grain constant. But neither Watts nor Joules have been dimensionless ever before. Nor the dimensions of the two measurements the same.

Perzactly, different dimensions.

Poor sod, this time it is you that was led into absurdity.

Nice clarification, thanks.

It might have been if he dug straight. He is so curly twisty that he is not more than 20 miles from home. Besides, he likes being the only person here that divides energy by impulse and calls it power gain.

you

never

have

Someone whom you brought here me energy over impulse.

Here you go John, your early post complete with headers:

Path: nlpi102-int.nbdc.sbc.com!flpi088.ffdc.sbc.com!prodigy.com!flpi089.ffdc.sbc.com!prodigy.net!newshub.sdsu.edu!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local02.nntp.dca.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Fri, 14 Nov 2008 10:45:22 -0600 From: John Larkin Newsgroups: sci.electronics.design Subject: Re: relays Date: Fri, 14 Nov 2008 08:45:23 -0800 Message-ID: References:

X-Newsreader: Forte Agent 1.91/32.564 MIME-Versi>>

Impulse? Impulse is measured in newton-seconds.

To get power gain, you divide power by power. Under specified conditions, you can get that same power gain by dividing energy by energy.

Go ahead, try a real example, with real units. Do the math. Look up a real relay datasheet and compute its power gain. Make and state any appropriate assumptions.

Try this one:

John

You are determined to paralyze yourself with complexity so you can't do any math.

John