Let's Take A Vote...

to

Kawaski Concours. And on rainy days an old Infinity J30.

give

limits to

particulates.

does,

suspended

current

The new Ford Fiesta has an automatic transmission like the A3, namely a dual-clutch 6-speed odd/even train with no torque converter. I think this is originally a Borg-Warner design.

John

Absolutely right. The way we talk about a 'capacitor's charge', using the Q=CV equation, relates to the absolute value of charge on each plate, one plate has +Q charge and the other -Q charge. The net charge on a capacitor is zero (it has to be, since the same current goes into a capacitor as comes out while 'charging' it, there can be no net gain or loss of charge inside the capacitor).

Therefore the 'capacitor's charge', by the definition above, is not conserved, but the net charge is. When talking about charge conservation we have to be careful about what our definitions of what we mean by 'charge' are.

I think John actually understands this, it's just the way it's put across leads others to come to different conclusions. In a quote from a post from the Magic Capacitors! thread he said to me: "We say that a capacitor stores charge, the amount being C*V in coulombs, and it works. My whole point, which has evoked such ranting, is that when you use this convention, be careful about designing using the concept that (this kind of) charge is always conserved."

Mark.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Nope, he has been talking all along about Q=CV by convention is the 'charge on a capacitor', which is the absolute value of charge on the plates (+Q and -Q respectively). With that definition of 'charge on a capacitor', he was not wrong. The net charge, +Q+(-Q), is zero, but this is conserved. You have lamented him because you didn't understand he was using that convention. I argued against it too, but I've read back all the posts he has written on this particular subject and he is consistent if you assume he is talking about that convention. As a result I posted an apology in the Magic Capacitor! thread.

Mark.

Well Thank You and Kudos, Mark, for being one of the few people capable of changing their mind and admitting it. (About their interpretation of what someone else meant, not the physics itself!).

--

John Devereux

"Charge " is just a word, and words are subject to different definitions by different people. I don't think many people here would get the reality wrong.

Engineers don't always use terms or methods that scientists would approve of. We do what works. When we do cheat the physics, we need to be careful.

John

es:

or

t

ch

arded

hen

he

,

he

,

the

, one

itor

comes

side

on we

ge'

oss

from

tores

, e s

"When we do cheat the physics" ... interesting concept.

comes

Yup. We use math that doesn't actually work, but gets close enough to do the job. We use terminology, like "charge", in our own way. We use empirical properties of things for which we have no theory or explanation. We do simulation and firmware where any concept of proper dimensional analysis is totally lost... just sling the numbers around until it works. We use proper physics when it helps, ignore it when it doesn't.

What's interesting is that most physicists are terrible electronic circuit designers, as their journals often show in hilarious ways.

One example is their devoted love of jfet differential pairs when the second fet isn't necessary and just multiplies the noise by sqrt(2). And their abiding affection for trimpots, as opposed to proper biasing design.

John

'Fraid to say this is not true, what we use are approximations to what we

*think* is the proper physics. The reality is all our physical laws cannot be proven to be correct, they only give consistent results with experiments. However, some of these laws seem to hold so universally that to challenge them would require significant experimental results to show inconsistency. We don't cheat physics, we approximate, sometimes as you say empirically when we have no model to use.

Or we just ignore it.

Physicists have a tricky moral and philosophical position: Physics describes the universe as it is, so, even though physicists are sometimes ignorant or wrong, Physics is always right. It's hard to argue with a viewpoint like that.

Physicists are bitch-slapped by reality. They discover things that are hinted at by the universe, and their theories are remorselessly accepted or trashed by that same universe. Engineers build stuff that, often, has never before existed in the history of the universe. I think that, over our careers, we generally have more fun and make more money.

John

comes

we

stores

Well, I would have said, appear to cheat...

Or is irrelevant, same thing?

Like the circuit in Wireless World I saw when a teenager for biasing one of those new LEDs with a temperature compensated voltage supply, while the rest of the world simply put in a dropping resistor?

I lost a bit of faith in published magazine circuits back then.

Dunno that one, I didn't use jfets in my designs, closest was the ujt (? 2n6027) which is more like an anode gate scr.

Well, I put four in recently, two I could do in software (zero), but the other two (span) work for me 'cos it's an integer only PIC chip doing the numbers, and I can't rely on the uC to "spackle over the holes" ;^)

I tend toward integer only fixed point numbers on 8bit controllers.

And, I may have a processing issue measuring very close to zero that the zero trimpots will help me put a number on. Prototypes are like that, anticipate issues then find different stuff one didn't think of.

Grant.

capacitor

comes

inside

we

from

stores

I do almost my embedded programming in bare-metal assembly, using scaled integer math. Calibrations are usually fractional multiplies. On a recent product, one advertised voltage range was +-2.56. The actual ADC span was about +-2.7. We read the ADC, subtract an offset cal factor, then multiply by a gain cal factor. The gain cal is nominally 1.05. So we multiply by 0.05 and add that to the code. The

0.05 is expressed as a 16-bit fractional, and the multiply is just a 16x16==>32 followed by a 16-bit right shift. "0.05" is expressed as integer 3277.

Of course, as you mention, codes are lost. One spacking technique is to oversample, calibrate, and lowpass filter.

John

Maybe you should eat breakfast, as soon as you get up? ;-)

=A0 =A0 ...Jim Thompson

=A0 =A0| =A0 =A0mens =A0 =A0 |

=A0 | =A0 =A0 et =A0 =A0 =A0|

=A0|

=A0 =A0 =A0 |

I believe charge is conserved 'by definition'. A charge is defined only in terms of a neutral substance being split into equal positive and negative charges. There is no other definition for a charge. All the theory of electricity follows from this 'assumption' or 'definition'.

[...]

Kinda late to the party there H.S. :) ...

--

John Devereux

Nah, I tried that--then all six mistakes happened while I was shaving and dressing, which made it too obvious for the rest of the day. One solution would be to wear a beard and have only one colour of socks, but I'm afraid to try that--who knows where the mistakes would happen then.)

On balance I'm better off this way. ;)

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

I do not connect every day. I just happened to see the post and replied to it. The thread seems to be live still (since July 23...)

Beard and only black socks and shoes works for me ;-)

Mistakes are the best way to learn. I can recall 47 years ago when our one-year-old daughter would run to Mommy, "Daddy is wading up paper and throwing it on the floor... again!" :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                   Spice is like a sports car... 
     Performance only as good as the person behind the wheel.

Beard and black socks for over 30 years, it works for me ;) Don't do much until coffee and medication take off. Or was that meditation and coffee? Hmm, depends how old you are.

I must have my one cup of good coffee made from fresh ground beans. I use a plunger, so it's a nice part of morning wakeup ritual. Water in kettle, coffee beans in grinder, just so many, and so on. I take long black, so it's to be dome right to get the crema (sp?) on top.

Idea of home roasting coffee sounds tempting too. There's avenues for proper temperature and profile control.

Grant.