Let's Take A Vote...
in [Design]
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From: John Larkin on 28 Jul 2010 19:08 On Wed, 28 Jul 2010 11:31:00 -0500, John Fields <jfields(a)austininstruments.com> wrote: >>What matters is that using a latching >>relay can extend battery life by thousands, maybe millions. > >--- >Thousands or millions of what, for heavens' sake??? Just thousands or millions. Hours/hours, or picoseconds/picoseconds, are simple dimensionless numbers. "Thousands" is dimensionless so doesn't need any more words. Some people would add the word "of times" or ":1" which are also dimensionless, so needn't be said. http://en.wikipedia.org/wiki/Dimensionless If I had wanted to specify the improvement in engineering units, I would have done so. But in this context, such units wouldn't make sense. You get so upset over basics like this. John
From: Grant on 28 Jul 2010 19:16 On Wed, 28 Jul 2010 07:03:02 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Wed, 28 Jul 2010 00:52:53 -0700, Robert Baer ><robertbaer(a)localnet.com> wrote: > >>John Fields wrote: >>> On Tue, 27 Jul 2010 07:01:58 -0700, John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> On Tue, 27 Jul 2010 04:00:22 -0500, John Fields >>>> <jfields(a)austininstruments.com> wrote: >>>> >>>> >>>>>> It has to do with >>>>>> getting SI units right. Did you ever read the wiki piece on >>>>>> dimensional analysis? Do you think it is smoke and mirrors? >>>>>> >>>>>> So, where did I say that charges can't generate forces? If you can't >>>>>> find such a statement, YOU are the one with emotions clouding your >>>>>> reason. >>>>> --- >>>>> Nonsense. >>>>> >>>>> All it means is that its location has slipped my mind, that the >>>>> message has been deleted or, who knows??? >>>> Who knows??? I know. You are deluded or just a liar. I would never say >>>> anything so silly. >>> >>> --- >>> You would, you have, and you will again, so you're the liar. >>> >>> "Latching relays have infinite gain." is a pretty silly thing to say, >>> yes? >>> >>> >>> JF >>> >> I think i "made a case" that the "gain" was not too hot, using rough >>numbers for input power to switch states, and power handling capability. >> For an infinite "gain", either the power to switch states must be >>zero, and/or the power handling capability must be infinite. >> Clearly, NEITHER exists. > >Power gain is Pload/(Pcoil*DutyCycle), where Dutycycle is the fraction >of time that the coil is energized. In plain English, power gain is >averaged load power divided by averaged coil power. That has no upper >bound as duty cycle approaches zero. In, say, a home thermostat that >uses one AA battery, Dutycycle might be a few tens of PPM, which is >why the battery will last a year or two. Probably the clock/LCD run >the battery down more than the relay does. > >So the argument devolves to whether a number that is unboundedly large >can be referred to as "infinite." Go for it. For some reasonably bounded value of infinite. Reminds me of the 2 + 2 = 5, for larger values of two :) People accept engineering roundoffs because to go finer, closer is buried in the noise or song of the universe. Grant. > >John >
From: John Larkin on 28 Jul 2010 21:31 On Sat, 24 Jul 2010 15:46:03 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Sat, 24 Jul 2010 11:24:55 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>Force is measured in newtons. Look it up. > >--- >As is the _mechanical_ force exerted by an electrical charge. > >For example, in the post I made from Schaum's, you obviously missed >supplemental problem 24 on page 144: > >Q. "If two equal charges, each of 1 coulomb, were separated in air by > a distance of 1km, what would be the force between them?" > >A. "9000 nt repulsion." >--- > > >>Now we have claims that coulombs, volts, and abvolts are all measures >>of force. Any other contributions? Can you measure force in >>milliseconds, or in henries? Do any units mean anything at all? > >--- >Well, by restating the problem like this: "What two like charges, >separated in air by a distance of 1km would cause a repulsive force >between them of 9000 nt?" ,it becomes obvious that charge can be a >measure of mechanical force since the answer is: "One coulomb each." > >As for volts and abvolts, I don't believe there's any question that >those are units of _electromotive_ force, do you? > > The term "electromotive force" was in use for over a hundred years before SI units were defined; the term is antique, and incorrect, and hardly anybody uses it in modern electronics. "Back EMF" is still sometimes used. We measure voltage in volts, force in newtons. Volts are not force. from http://en.wikipedia.org/wiki/Electromotive_force#Terminology ================== The term electromotive force is due to Alessandro Volta (1745�1827), who invented the battery, or voltaic pile. "Electromotive force" originally referred to the 'force' with which positive and negative charges could be separated (that is, moved, hence "electromotive"), and was also called "electromotive power" (although it is not a power in the modern sense). Maxwell's 1865 explanation of what are now called Maxwell's equations used the term "electromotive force" for what is now called the electric field strength.[10]. But, in his later textbook[11] he uses the term "electromotive force" both for "voltage-like" causes of current flow in an electric circuit, and (inconsistently) for contact potential difference (which is a form of electrostatic potential difference). Given that Maxwell's textbook was written before the discovery of the electron, it is understandable that Maxwell exhibits what (in terms of modern knowledge) is inconsistency in the use of the term "electromotive force". The word "force" in "electromotive force" is a misnomer:[12] "[Electromotive force] has turned out to be an unfortunate choice of words which is still with us 160 years later. In all of physics except electromagnetic induction, the term 'force' is reserved for mechanical action on ponderable matter and is measured in units called Newtons. In contrast electromotive force is measured in units of Volts and causes charge separation." ================== John
From: Robert Baer on 29 Jul 2010 01:35 John Larkin wrote: > On Wed, 28 Jul 2010 00:52:53 -0700, Robert Baer > <robertbaer(a)localnet.com> wrote: > >> John Fields wrote: >>> On Tue, 27 Jul 2010 07:01:58 -0700, John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> On Tue, 27 Jul 2010 04:00:22 -0500, John Fields >>>> <jfields(a)austininstruments.com> wrote: >>>> >>>> >>>>>> It has to do with >>>>>> getting SI units right. Did you ever read the wiki piece on >>>>>> dimensional analysis? Do you think it is smoke and mirrors? >>>>>> >>>>>> So, where did I say that charges can't generate forces? If you can't >>>>>> find such a statement, YOU are the one with emotions clouding your >>>>>> reason. >>>>> --- >>>>> Nonsense. >>>>> >>>>> All it means is that its location has slipped my mind, that the >>>>> message has been deleted or, who knows??? >>>> Who knows??? I know. You are deluded or just a liar. I would never say >>>> anything so silly. >>> --- >>> You would, you have, and you will again, so you're the liar. >>> >>> "Latching relays have infinite gain." is a pretty silly thing to say, >>> yes? >>> >>> >>> JF >>> >> I think i "made a case" that the "gain" was not too hot, using rough >> numbers for input power to switch states, and power handling capability. >> For an infinite "gain", either the power to switch states must be >> zero, and/or the power handling capability must be infinite. >> Clearly, NEITHER exists. > > Power gain is Pload/(Pcoil*DutyCycle), where Dutycycle is the fraction > of time that the coil is energized. In plain English, power gain is > averaged load power divided by averaged coil power. That has no upper > bound as duty cycle approaches zero. In, say, a home thermostat that > uses one AA battery, Dutycycle might be a few tens of PPM, which is > why the battery will last a year or two. Probably the clock/LCD run > the battery down more than the relay does. > > So the argument devolves to whether a number that is unboundedly large > can be referred to as "infinite." Go for it. > > John > > By your own statement, you admit that the duty cycle IS NOT ZERO, and therefore there IS a bound. And "duty cycle" does not cut it; if so, one could take a very large (latching, if that "helps") relay and operate it *once* using its required 200KW of power, to control one microwatt of load - and "therefore" have an absurdly large "gain" based on the "duty cycle" of almost zero.
From: Phil Hobbs on 29 Jul 2010 01:53
Robert Baer wrote: > John Larkin wrote: >> On Wed, 28 Jul 2010 00:52:53 -0700, Robert Baer >> <robertbaer(a)localnet.com> wrote: >> >>> John Fields wrote: >>>> On Tue, 27 Jul 2010 07:01:58 -0700, John Larkin >>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>> On Tue, 27 Jul 2010 04:00:22 -0500, John Fields >>>>> <jfields(a)austininstruments.com> wrote: >>>>> >>>>> >>>>>>> It has to do with >>>>>>> getting SI units right. Did you ever read the wiki piece on >>>>>>> dimensional analysis? Do you think it is smoke and mirrors? >>>>>>> >>>>>>> So, where did I say that charges can't generate forces? If you can't >>>>>>> find such a statement, YOU are the one with emotions clouding your >>>>>>> reason. >>>>>> --- >>>>>> Nonsense. >>>>>> >>>>>> All it means is that its location has slipped my mind, that the >>>>>> message has been deleted or, who knows??? >>>>> Who knows??? I know. You are deluded or just a liar. I would never say >>>>> anything so silly. >>>> --- >>>> You would, you have, and you will again, so you're the liar. >>>> >>>> "Latching relays have infinite gain." is a pretty silly thing to say, >>>> yes? >>>> >>>> >>>> JF >>> I think i "made a case" that the "gain" was not too hot, using >>> rough numbers for input power to switch states, and power handling >>> capability. >>> For an infinite "gain", either the power to switch states must be >>> zero, and/or the power handling capability must be infinite. >>> Clearly, NEITHER exists. >> >> Power gain is Pload/(Pcoil*DutyCycle), where Dutycycle is the fraction >> of time that the coil is energized. In plain English, power gain is >> averaged load power divided by averaged coil power. That has no upper >> bound as duty cycle approaches zero. In, say, a home thermostat that >> uses one AA battery, Dutycycle might be a few tens of PPM, which is >> why the battery will last a year or two. Probably the clock/LCD run >> the battery down more than the relay does. >> >> So the argument devolves to whether a number that is unboundedly large >> can be referred to as "infinite." Go for it. >> >> John >> >> > By your own statement, you admit that the duty cycle IS NOT ZERO, and > therefore there IS a bound. > And "duty cycle" does not cut it; if so, one could take a very large > (latching, if that "helps") relay and operate it *once* using its > required 200KW of power, to control one microwatt of load - and > "therefore" have an absurdly large "gain" based on the "duty cycle" of > almost zero. > The amount of bandwidth we've been wasting recently on exactifussitudes like this makes arguing about angels dancing on the head of a pin seem positively practical. Personally, I make an average of about six stupid mistakes before breakfast, so I'm used to it by now. Fields has a private meaning for the word 'force', and Larkin is using 'infinite' in a loose sense. As the cop said to Jack Nicholson in the last scene of the movie, "Forget it, Jake--it's Chinatown." Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |