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Measuring PWM current?

Started by Spare Change April 29, 2019
bill....@ieee.org wrote:
> > > And here I was thinking that this thread had been moderately civil and useful. >
** Can I remind you this IS usenet you know ? Where no good post ever goes unpunished.
> Phil Alison is easy to irritate, >
** Particularly if folk misspell my name ;-)
> and we had seemed to be doing a decent job of not irritating him. >
** Normally I am polite and slow to anger, as anyone who knows me would tell you. But there is only so much BS this Koala can bear, I then leave the other party in no doubt about what I think of them.
> Now you blow it, for absolutely no useful purpose. >
** The Chirping Cricket is a long time poster on "aus.electronics" and lives here in Australia. That NG has virtually disappeared, through no fault of mine or his. Fas as I know, he is purely a hobbiest.
> And I very much doubt if Phil Alison gives a toss how Win Hill makes > his money. >
** I suspect he makes it a more easily than I do.
> He does seem to care about having stuff stated clearly and simply, > which is an attitude I share. >
** I learned the art while writing numerous construction articles for "Electronics Australia" magazine. My aim was to leave nothing for the editor to mess with.
> An assumption of too much background knowledge for the people who read > this group is a perennial problem. >
** It is tempting for a well informed person to talk over others heads and amaze them with their knowledge. But beware, charlatans do exactly the same with almost no knowledge. Readers may not be able to tell the difference. .... Phil
On Tuesday, April 30, 2019 at 10:52:32 PM UTC+10, palli...@gmail.com wrote:
> bill....@ieee.org wrote: > > > > > > And here I was thinking that this thread had been moderately civil and useful. > > > > ** Can I remind you this IS usenet you know ? > > Where no good post ever goes unpunished.
Too true,
> > Phil Alison is easy to irritate, > > > > ** Particularly if folk misspell my name ;-)
Oops. Sorry about that.
> > and we had seemed to be doing a decent job of not irritating him. > > > > ** Normally I am polite and slow to anger, as anyone who knows me would tell you. But there is only so much BS this Koala can bear, I then leave the other party in no doubt about what I think of them.
We've noticed.
> > Now you blow it, for absolutely no useful purpose. > > > > ** The Chirping Cricket is a long time poster on "aus.electronics" and lives here in Australia. That NG has virtually disappeared, through no fault of mine or his. Fas as I know, he is purely a hobbiest. > > > And I very much doubt if Phil Alison gives a toss how Win Hill makes > > his money. > > > > ** I suspect he makes it a more easily than I do.
Don't knock "The Art of Electronics". It contains lots of good stuff. Luck always plays a part in the way you get to earn your living, and he does seem to have been in the right place at the right time to be able to sell his skills into a market that seems to pay well, but they aren't inconsiderable skills.
> > He does seem to care about having stuff stated clearly and simply, > > which is an attitude I share. > > ** I learned the art while writing numerous construction articles for "Electronics Australia" magazine. My aim was to leave nothing for the editor to mess with. > > > An assumption of too much background knowledge for the people who read > > this group is a perennial problem. > > > > ** It is tempting for a well informed person to talk over others heads and amaze them with their knowledge.
Total waste of time, though.
> But beware, charlatans do exactly the same with almost no knowledge.
Too true, which is another reason for keeping the message clear and easily comprehensible.
> Readers may not be able to tell the difference.
And don't seem to pay much attention even when the difference is spelled out in some detail. -- Bill Sloman, Sydney
[Trimming the many unnecessary blank lines from PA's news agent again]

On 30/4/19 10:18 pm, pallison49@gmail.com wrote:
> Clifford the Chirping Cricket know nothing wrote: >>>> That was a useful contribution, to me anyway. >>> ** Win can interpret his own posts, thankyou. >>>>> A clear explanation in plain English is much preferable >>>> It seemed pretty clear to me. >>> ** You have way over-snipped and posted a comment about yourself - which is impossible for others to interpret with any certainty. >> Bullshit, stop being a dick. > ** Simple fact and you are the "dick". >> I quoted *all text* prior to you asking "Your point being?". Check it >> yourself! > ** All of which Win wrote, it was MY stuff you over-snipped. >> I only deleted *blank lines* and the following context - which >> I was not responding to. > ** That is a great big lie as anyone can see.
Ok smart-arse. Which was the first word I clipped? You want to make a claim, you have to defend it. You are the liar here, as anyone can check.
> You posted an unsupported opinion which equates to comment about YOURSELF. > I have no clue why you think it, so no reply is possible.
You have no clue why I found Win's response helpful? I'm not qualified to comment on your mental incapacities, but his writing seemed clear enough to me. On reflection I'm not sure he was right, but I'll say why on another post.
>> You don't like me calling you out for playing dumb ... > ** Huh ?? > I never play dumb, I do sometimes call folk's bluff when they fail to explain their posts. >> and attacking Win > ** No, my post was purely in self defence, cos I rightfully object to being treated like a pupil by anyone. >> because you're envious of him having a real job where >> someone cares about what he does? > ** Ok folks, I think we have a loyal "Win fan" here and I have upset him with my comments. Fraid they all went right over his head.
It's true I admire Win for being a gentleman and never "playing the man" the way you (and sometimes, I) do. In this group, only PhilH and Joerg join him in having that level of maturity. Thanks, guys. Clifford Heath
On 29/4/19 6:45 pm, Winfield Hill wrote:
> pallison49@gmail.com wrote... >> Spare Change wrote: >>> Can an RMS current clamp meter accurately measure >>> the current of a PWM voltage? >> ** Yes, with two conditions. >> 1. The clamp meter is a DC /AC type, using Hall effect sensing. >> 2. The frequencies involved do not exceed the meter's range, >> which may be only 1kHz. >>> How else to measure PWM current without a shunt or direct in-line meter? >> ** A Hall effect current sensor followed by a true RMS meter - >> both with adequate bandwidth which must be several times the >> PWM frequency. > A typical hall-effect current sensor, including the sensor > for a DC clamp meter, creates a current through a secondary > coil, that nulls the magnetic field at the Hall sensor. If > the sensed current changes much faster than the speed of the > Hall-sensor current loop, isn't it likely the loop responds > to the average of the input current? If the OP's PWM system > is DC, of one polarity, he'd get an average measurement. But > if he's got an AC current, then yes, the Hall sensor needs > to be much faster than the effective AC frequency, to follow. > Any RMS calculations would be performed after the sensor. In > both cases high-frequency PWM could be averaged by the sensor.
Win, Are you describing a servo loop here, that produces a servo current to cancel the average field at the Hall sensor? If so, how does the averaging preserve RMS measurement? If not, can you explain more clearly what you mean? Because I think Phil is right here, even though he expresses himself unpleasantly. Clifford Heath.
Clifford the Fuckwit Cricket puked: 

> > >>>> That was a useful contribution, to me anyway. > >>> ** Win can interpret his own posts, thankyou. > >>>>> A clear explanation in plain English is much preferable > >>>> It seemed pretty clear to me. > >>> ** You have way over-snipped and posted a comment about yourself - which is impossible for others to interpret with any certainty. > >> Bullshit, stop being a dick. > > ** Simple fact and you are the "dick". > >> I quoted *all text* prior to you asking "Your point being?". Check it > >> yourself! > > ** All of which Win wrote, it was MY stuff you over-snipped. > >> I only deleted *blank lines* and the following context - which > >> I was not responding to. > > ** That is a great big lie as anyone can see. > > Ok smart-arse.
** Fuck you.
> Which was the first word I clipped?
** Read you own post, fuckhead, see how much of my post to Win is missing.
> You want to make a claim, you have to defend it.
** Shame you do not follow that same principle.
> > You are the liar here,
** You have completely lost it. You in love with Win or something ?
> > You posted an unsupported opinion which equates to comment about YOURSELF. > > I have no clue why you think it, so no reply is possible. > > You have no clue why I found Win's response helpful?
** Read you own post - that is not the question.
> I'm not qualified > to comment on your mental incapacities, but his writing seemed clear > enough to me. >
** Again, an uninformative comment about YOURSELF.
> On reflection I'm not sure he was right, but I'll say why on another post.
** The Chirping Cricket certainly has lost it.
> >> You don't like me calling you out for playing dumb ... > > ** Huh ?? > > I never play dumb, I do sometimes call folk's bluff when they fail to explain their posts. > >> and attacking Win > > ** No, my post was purely in self defence, cos I rightfully object to being treated like a pupil by anyone. > >> because you're envious of him having a real job where > >> someone cares about what he does? > > ** Ok folks, I think we have a loyal "Win fan" here and I have upset him with my comments. Fraid they all went right over his head. > > > It's true I admire Win for being a gentleman and never "playing the man" > the way you (and sometimes, I) do.
** I never play the man, ever. It only looks that way to folk who cannot follow a thread or do not read ALL the words in ALL the posts. Like you.
> In this group, only PhilH and Joerg > join him in having that level of maturity.
** In order to judge maturity, you have to have some yourself. Counts you straight out. In order to judge an argument, you must know who is wrong and who is not. Counts you straight out again. Though one party may appear to be more polite, that proves NOTHING. Charlatans and bullshit artists often EXCELL at playing the polite game. Only fools fall for it. FYI: Closing up the text of a thread makes it damn hard to read. The blank lines are there to facilitate reading and replying. .... Phil
On Wednesday, May 1, 2019 at 11:08:41 AM UTC+10, Clifford Heath wrote:
> On 29/4/19 6:45 pm, Winfield Hill wrote: > > pallison49@gmail.com wrote... > >> Spare Change wrote: > >>> Can an RMS current clamp meter accurately measure > >>> the current of a PWM voltage? > >> ** Yes, with two conditions. > >> 1. The clamp meter is a DC /AC type, using Hall effect sensing. > >> 2. The frequencies involved do not exceed the meter's range, > >> which may be only 1kHz. > >>> How else to measure PWM current without a shunt or direct in-line meter? > >> ** A Hall effect current sensor followed by a true RMS meter - > >> both with adequate bandwidth which must be several times the > >> PWM frequency. > > A typical hall-effect current sensor, including the sensor > > for a DC clamp meter, creates a current through a secondary > > coil, that nulls the magnetic field at the Hall sensor. If > > the sensed current changes much faster than the speed of the > > Hall-sensor current loop, isn't it likely the loop responds > > to the average of the input current? If the OP's PWM system > > is DC, of one polarity, he'd get an average measurement. But > > if he's got an AC current, then yes, the Hall sensor needs > > to be much faster than the effective AC frequency, to follow. > > Any RMS calculations would be performed after the sensor. In > > both cases high-frequency PWM could be averaged by the sensor. > > Are you describing a servo loop here, that produces a servo current to > cancel the average field at the Hall sensor? If so, how does the > averaging preserve RMS measurement?
It doesn't, whence the line "A Hall effect current sensor followed by a true RMS meter - both with adequate bandwidth which must be several times the PWM frequency." In reality the PWM frequency isn't the crucial variable - the current sensor and the meter have to be able to follow the narrowest current peak in the waveform. A train of 1usec spikes repeating at 100Hz won't be correctly evaluated by a current sensor and RMS meter with a bandwidth of only several hundred Hz. <snip>
bill....@ieee.org wrote:

> > > ** Can I remind you this IS usenet you know ? > > > > Where no good post ever goes unpunished. > > Too true, > > > > > And I very much doubt if Phil Alison gives a toss how Win Hill makes > > > his money. > > > > > > > ** I suspect he makes it a more easily than I do. > > Don't knock "The Art of Electronics".
** Huh ? How the hell did you get that from my post ?
> > ** It is tempting for a well informed person to talk over others heads > > and amaze them with their knowledge. > > Total waste of time, though. > > > But beware, charlatans do exactly the same with almost no knowledge. > > Too true, which is another reason for keeping the message clear > and easily comprehensible. > > > Readers may not be able to tell the difference. > > And don't seem to pay much attention even when the difference is > spelled out in some detail. > >
** Charlatans appeal to people's emotions, which in most cases are much stronger that their thoughts. Old saying: " You cannot reason a person out of a position that reason never got them into in the first place. " .... Phil
On Wednesday, May 1, 2019 at 11:55:19 AM UTC+10, palli...@gmail.com wrote:
> bill....@ieee.org wrote: > > > > > > ** Can I remind you this IS usenet you know ? > > > > > > Where no good post ever goes unpunished. > > > > Too true, > > > > > > > > And I very much doubt if Phil Alison gives a toss how Win Hill makes > > > > his money. > > > > > > > > > > ** I suspect he makes it a more easily than I do. > > > > Don't knock "The Art of Electronics". > > ** Huh ? How the hell did you get that from my post ?
The implication that I had in mind was that you might have thought that it could have been easier to write "The Art of Electronics" than it was to make money whatever way you do. That strikes me as representing an imperfect appreciation of the quality of "The Art of Electronics" - more along the lines of insufficient adulation rather than actual criticism. <snip>
> ** Charlatans appeal to people's emotions, which in most cases are much stronger that their thoughts. > > Old saying: > > " You cannot reason a person out of a position that reason never got them into in the first place. "
Good point. Charlatans frequently use a lot of flattery to lubricate their message. -- Bill Sloman, Sydney
bill....@ieee.org wrote:

>
> > > > > > > > > > > > > ** I suspect he makes it a more easily than I do. > > > > > > Don't knock "The Art of Electronics". > > > > ** Huh ? How the hell did you get that from my post ? > > > The implication that I had in mind was that you might have thought > that it could have been easier to write "The Art of Electronics" > than it was to make money whatever way you do. >
** Fact is, it never occurred to me the royalties on a technical book was Win's only income. Does he not hold an academic position ?
> > > ** Charlatans appeal to people's emotions, which in most cases are much stronger that their thoughts. > > > > Old saying: > > > > " You cannot reason a person out of a position that reason never got > > them into in the first place. " > > Good point. Charlatans frequently use a lot of flattery to lubricate > their message. > >
** I was thinking more of making appeals to common prejudices, myths and false assumptions. A well manufactured lie is often much easier to believe than a confronting truth. .... Phil
On Wednesday, May 1, 2019 at 12:31:42 PM UTC+10, palli...@gmail.com wrote:
> bill....@ieee.org wrote: > > > > > > > > > > ** I suspect he makes it a more easily than I do. > > > > > > > > Don't knock "The Art of Electronics". > > > > > > ** Huh ? How the hell did you get that from my post ? > > > > The implication that I had in mind was that you might have thought > > that it could have been easier to write "The Art of Electronics" > > than it was to make money whatever way you do. > > ** Fact is, it never occurred to me the royalties on a technical book was Win's only income.
It clearly isn't, but successful textbooks can provide a very useful income stream.
> Does he not hold an academic position?
The Rowland Institute for Science merged with Harvard University in 2003 (according to the biographical data in the front of AoE3). So he is now a university employee, but probably not in an academic position. Paul Horowitz is a professor at Harvard, and thus definitely an academic
> > > ** Charlatans appeal to people's emotions, which in most cases are much stronger that their thoughts. > > > > > > Old saying: > > > > > > " You cannot reason a person out of a position that reason never got > > > them into in the first place. " > > > > Good point. Charlatans frequently use a lot of flattery to lubricate > > their message. > > ** I was thinking more of making appeals to common prejudices, myths and false assumptions. > > A well manufactured lie is often much easier to believe than a confronting truth.
Too true, and it's easy to fiddle with a lie to make it really easy to swallow. The truth is less flexible. -- Bill Sloman, Sydney