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Actually, the first potentiometers were used (and still are) as
voltage-measuring instruments:
http://en.wikipedia.org/wiki/Potentiometer-(measuring_instrument)
and, as far as I know, are still called 'potentometers' today, around
the world.
What has come to be known as a "pot", colloquially, is essentially the
same thing; a fixed resistance with a movable contact allowing it to
be used as a three terminal adjustable voltage divider, while a
rheostat is a two-terminal device used as a variable resistor and, is,
therefore, used to adjust current.
http://en.wikipedia.org/wiki/Potentiometer
Could you be a little more specific? A 10-bit accurate sine wave value changes by 0.1% of full scale fom one value to the next. If you want the fastest changing part of your waveform to change by 0.1% per step, you need about 3000 samples per cycle, but 2000 is close enough. For any kind of pulse width modulation, a 0.1% resolution in amplitude implies a 0.1% resolution in where you place your switching point within the pulse period - for a 50usec wide pulse, that implies 50nsec resolution in edge position, or a 20MHz clock.
Not that it couldn't be done, but that the OP would probably not choose to do it that way. Your persistence with the claim that I'm lying does suggest that you are suffering from severe brain damage.
That goes to show just how much you scrutinize postings.
No, but he's not afraid to suggest using it to save time over a ridiculous re'engineering of a basic concept that's been around for decades. If power consumption, space and speed were an issue, along with demand in it's use, I suppose it would be worthy to use an alternative component. But It seems that even new designs todate, are still using it, and for good reason, One that you can't seem to reconcile with.
Another proof that you don't absorb postings very well or is Alzheimer's kicking in? Have you been regressing lately, playing with your marbles ?
Jim is just being polite . As you suggest, he has some common sense and thus, that sense tells him you are hopeless.
The current is far to strong for you to back paddle your way up stream there old man!
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I have, and your remark that "rheostat is antidiluvian" is what
prompted me to reply; not only to show that it's certainly as modern
as "potentiometer" - which is not at all antediluvian - but also that
when used correctly it's perfectly proper. ^
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If you read a little more carefully I think you'll find that Michael's
response was in reply to your statement that "Potentiometer has been
pot here in the UK for many decades." and was meant to convey that a
pot can also be used as a rheostat, regarless of the name.
I don't understand what you mean by "out of fashion".
If you don't call a rheostat a rheostat, what _do_ you call it?
Of course it can - short the wiper to one end. I took him to mean that rheostat could be either which is clearly nonsense.
Trimpot. Rheostat has pretty much dropped out of the lexicon here. I can't remember when I last saw a real rheostat used but it was several decades ago. They were out evolved by solid state power controllers.
I am now more mystified than ever as to whether the term rheostat still has currency in electronics across the pond.
All the (non-semiconductor) variable resistors we have in stock have three leads, and we call them "pots." Nobody in our shop uses the term "rheostat."
To me, a rheostat is a huge wirewound thing, like theatre lighting used to use before the SCR (or the Variac) was invented. We don't use them in our electronic instruments. We don't even use "rheostats" as dummy loads... we have nice Kikusui electronic load boxes for that.
It has been and still be that way, at least in our shop for years..
Rheostat:
Open body, wire wound resistor, non precision and designed for high power applications usually wound on a high temperature form, like ceramic for example.
The key here is, Open Body containment and they don't need to be on a rotary form, they can be a sliding high power resistor.. they come in 2 or more terminals.
All other devices are enclosed due to low power to keep the surfaces clean. Because the lack of higher power wiping (Rheostats) does not perform the "Wetting" process. Wire wound, carbon, conductive plastics that need to be covered have landed in the "Potentiometer" class because of what it does as it's job, not how its constructed. Both can serve as a variable reference but construction normally signifies the differences and it's usage's when it comes to power levels or precision.
Take a precision 10T wire pot apart so that it's core is exposed, you basically have now a Rheostat how ever, because its now exposed to a more harsh environment, it wound most likely give up the ghost before you get appreciable use out of it. Most of these 10T are not designed for high wattage use.
That is the info I have to go on when I need to order parts for a project or replacement, it seems that most manf I've found follow these rules..
We have 300 Watt resistors with a sliding tap on them and they are ordered as high power Rheostat resistors.
And to top it off, be careful, I've seen good many people get a charge of their life when attempting to adjust these things, ALIVE.
Thats not really how it works, if it were at those 1bit audio dacs would need a ~2.8 GHz time base. They use deltasigma, but the same goes for PWM (except maybe at DC, depending on how you do it)
imagine a 10Hz square wave and a perfect brick wall lowpass filter at a little over 10Hz
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You don't even have to; just use the wiper and whichever end gives you
the handedness you want.
There _is_ a fairly good reason for shorting to one end though; do you
know what it is?
Exploration of human pathology, especially the distortions that emotion make onto thinking. In complex systems, that is often the limiting factor on performance.
I just got off a half-hour conference call that nicely illustrates that point. People aren't thinking clearly, or doing the logical things to solve a problem, because their emotions are involved.
Engineering is, paradoxically, a very emotional business.
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