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'[PIC] Protecting PIC A/D inputs'
2004\09\10@014151 by PicDude

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face
Thanks for the reponses.  I'll respond to a bunch of them here....

- The sender is a fuel sender, GM style (240-33 ohm).  I use a 240 ohm
resistor for the upper part of the voltage divider (between the PIC A/D input
and +5V), and the fuel sender forms the lower part of the voltage divider.  
So the max A/D input signal voltage is 2.5V, and the impedance is 120 ohms
max.

- Although I am calculating this for a fuel sender, a similar arrangement will
be used for an oil-pressure sender.

- Vref is 2.5V and is externally supplied to the PIC, using 2 equal-valued
resistors that form another voltage divider between +5V and ground.  This
makes the whole arrangement ratiometric.

- Now that I think about it a bit more, since the A/D voltage is only up to
2.5V, I should change the proposed zener a 4.7V or 4.3V type.  I'll download
and look at some zener datasheets after this to see what effects I can expect
up to 2.5V.

- Good point on using a schottky for D2 so it would conduct before the
internal protection diode.  I've got some BATxx types around here somewhere,
so I'll check what I have specifically.  IIRC, the internal protection diodes
on the PIC A/D inputs are 0.6V types, so I'll have to ensure that it's below
that.

- If I were to use a current-limiting resistor on the inputs, then that will
have some effect on the actual measured value at the input pin, and the
charging time for the internal hold capacitor, right?  How would I calculate
for the effects of this?

Cheers,
-Neil.




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2004\09\10@082105 by Gerhard Fiedler

picon face
>> How about using a standard RC low pass, with a resistor that's bigger
>> than the PIC ADC input likes, but with a capacitor that's big enough to
>> load the PIC's internal cap with an error that's below your
>> requirements?
>
> The capacitor does nothing about the PIC A/D input leakage currents times
> the source resistance causing an offset.  In addition the capacitor low pass
> filters the sample and hold capacitor charge current, so the voltage at the
> pin becomes a function of the average charge current, which is a function of
> the voltage on the sample and hold cap before the acquitision, which is a
> function of the voltage on the previously selected analog channel.  In other
> words, you have no created a charge pump from the previous analog channel to
> this one, requiring much longer acquisition times than usual to get around.

Hm...

Imagine a 100n cap at the input (5 V, 8 bit, 20 mV/digit). It's about 2000
times the ADC capacitor (50p), which means that charging the ADC sampling
cap to either end of the range doesn't change the total voltage by more
than 1/2000 of the maximum voltage difference, or < 3 mV. This seems
negligible.

During the sample period of max 15 us, the voltage at the input changes by
less than 500 nA * 15 us / 100 nF < 100 uV, so that's negligible too.

Then there's the input leakage current of 500 nA. With 0.5 LSB max error,
that would be a max input resistor of 20k.

In summary, it seems the really limiting factor for the input resistor is
the input leakage current (as Russell said), and otherwise the capacitor
works well as a low impedance voltage source for the ADC input.

Gerhard
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2004\09\10@082450 by olin_piclist

face picon face
PicDude wrote:
> - The sender is a fuel sender, GM style (240-33 ohm).  I use a 240 ohm
> resistor for the upper part of the voltage divider (between the PIC
> A/D input and +5V), and the fuel sender forms the lower part of the
> voltage divider.
> So the max A/D input signal voltage is 2.5V, and the impedance is 120
> ohms max.

Since fuel level changes slowly, you can (and should) low pass filter it
heavily.  You can easily ignore frequencies above 100mHz without missing any
real data.

> - Although I am calculating this for a fuel sender, a similar
> arrangement will be used for an oil-pressure sender.

There you might want to heavily filter above 1Hz.  That still gives lots of
opportunity for noise reduction.

> - Vref is 2.5V and is externally supplied to the PIC, using 2
> equal-valued resistors that form another voltage divider between +5V
> and ground.  This makes the whole arrangement ratiometric.

This is silly.  The 2.5V reference is still relative to the +5V supply, only
that it has additional error due to the divider resistors.  Your reading is
rationmetric because the same +5V sources the current for the resistive
sensor, not because you divided it to make the A/D reference.  It would
still be ratiometric if the +5V was used as the PIC Vdd, which was used as
the A/D reference.  The main difference is that you now have a 5V A/D input
range, a good place to clamp the incoming signal to, and no error on the A/D
reference with respect to the pullup voltage on the resistive sensor.


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2004\09\10@083640 by Gerhard Fiedler

picon face
> Again, assume that the wire coming in will have occasional short spikes
> of 200V and figure out what that will do.

When you say "short spikes", do you have an idea what "short" means? ns,
us, ms range?

Thanks,
Gerhard
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2004\09\10@092145 by olin_piclist

face picon face
Gerhard Fiedler wrote:
> Imagine a 100n cap at the input (5 V, 8 bit, 20 mV/digit). It's about
> 2000 times the ADC capacitor (50p), which means that charging the ADC
> sampling
> cap to either end of the range doesn't change the total voltage by
> more
> than 1/2000 of the maximum voltage difference, or < 3 mV. This seems
> negligible.

Yes, for one sample.  You are really moving a fixed charge every time the
input channel is sampled.  That charge times the sample frequency is a
current.  That current times the source resistance is an offset voltage.
Note that the capacitor value doesn't enter into this equation as long as
it's big enough to carry most of the accumulated charge from one sample to
the next.  Your logic above only holds when there is no "memory" from one
sample to the next.

Of course this is assuming the A/D channel is being switched, in other words
two or more analog voltages being constantly sampled.  If the A/D channel is
left fixed, then there is no charge pump between channels.


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2004\09\10@092533 by olin_piclist

face picon face
Gerhard Fiedler wrote:
>> Again, assume that the wire coming in will have occasional short
>> spikes of 200V and figure out what that will do.
>
> When you say "short spikes", do you have an idea what "short" means?
> ns, us, ms range?

I would want it to survive at 200V for a few 100uS.  You can assume the
repition of these events are low so that the average power can be ignored,
but the instantaneous spike must not damage anything.


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2004\09\10@092722 by Russell McMahon

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> Since fuel level changes slowly, you can (and should) low pass filter it
> heavily.  You can easily ignore frequencies above 100mHz

= 0.1 Hz

> without missing any real data.

> > - Although I am calculating this for a fuel sender, a similar
> > arrangement will be used for an oil-pressure sender.

> There you might want to heavily filter above 1Hz.  That still gives lots
of
> opportunity for noise reduction.

I agree that filtering is wise. But I would probably reverse those filter
time constants myself.
Petrol level in a normal tank does not vary significantly over seconds and
hardly so over minutes.

However, an oil pressure gauge can tell you useful things over periods of
well under a second. If yours ever DOES tell you useful things in such short
periods your engine is probably in deep trouble, but that's the whole point.

I once, long ago, had a vehicle where both the above applied! :-)

For example: The time the oil pressure takes to rise to a steady value on
startup, the behaviour on idling and throttle blipping and the time to fall
when the engine is turned off all tell you things about engine condition.
Oil systems using a positive displacement pump have a pressure relief valve
and a vehicle in good condition will have the oil pressure sit at the relief
vale setting under almost all conditions. When the pressure reduces while
operating eg between gear changes you know you have problems :-)

While running the oil above minimum on the dip stick is the norm, it doesn't
always happen that way. Despite years of knowing better I dipped a sump
yesterday where the oil level was almost off the bottom of the dipstick. As
sump level drops to critical an engine may oil starve when cornering one way
or the other or while braking/accelerating, with a sudden but usually brief
drop in oil pressure. While this is an extreme and undesirable condition, it
is nice if the oil gauge indicates it visually.


       RM

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2004\09\10@101953 by Gerhard Fiedler

picon face
> - If I were to use a current-limiting resistor on the inputs, then that will
> have some effect on the actual measured value at the input pin, and the
> charging time for the internal hold capacitor, right?  How would I calculate
> for the effects of this?

In the ADC section of the datasheets they usually give the formulas
involved and an example calculation for the effect of an input resistor on
the required acquisition time.

Regarding the effect of the input leakage current on the measured voltage,
you simply multiply your input resistor with the maximum leakage current,
which gives you the maximum voltage error for this resistor.

Gerhard
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2004\09\10@103927 by olin_piclist

face picon face
Russell McMahon wrote:
> I agree that filtering is wise. But I would probably reverse those
> filter time constants myself.
> Petrol level in a normal tank does not vary significantly over
> seconds and hardly so over minutes.
>
> However, an oil pressure gauge can tell you useful things over
> periods of well under a second.

Right.  I suggested 100mHz = .1Hz low pass for the fuel and 1Hz low pass for
oil pressure.  In other words, around 10 second response to fuel and 1
second response to oil pressure.


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2004\09\10@105553 by Dave VanHorn

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>
>Right.  I suggested 100mHz = .1Hz low pass for the fuel and 1Hz low pass for
>oil pressure.  In other words, around 10 second response to fuel and 1
>second response to oil pressure.

If your fuel is changing faster than that, you have LARGE problems! :)

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2004\09\10@112648 by Bob J

picon face
On Fri, 10 Sep 2004 08:24:46 -0400, Olin Lathrop
<spam_OUTolin_piclistTakeThisOuTspamembedinc.com> wrote:
> PicDude wrote:
> > - The sender is a fuel sender, GM style (240-33 ohm).  I use a 240 ohm
> > resistor for the upper part of the voltage divider (between the PIC
> > A/D input and +5V), and the fuel sender forms the lower part of the
> > voltage divider.
> > So the max A/D input signal voltage is 2.5V, and the impedance is 120
> > ohms max.

I have a similar project that uses 240 ohm fuel senders, but I did not
run that high of a voltage to the sender.  The divider from 5v is a
24K resistor so that the voltage at the sender is 0-50mV, not 2.5V.
In an automotive environment the load dump conditions are horrendous
(example: turn off the headlights and the regulator overshoots by 300
volts for a few uS).  With that in mind I thought it was a safe idea
to use a very low voltage in the sender/divider circuit (not that it
would really matter since my supply is filtered), then use opamps to
isolate and scale/offset for .5-4.5 volt range at the adc.  Any
voltages above or below that means there's a fault in the system.  I
believe 0-50mV is the "standard" for automotive senders.

Regards,
Bob
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2004\09\10@115648 by Support - KF4HAZ

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face
Actually I have helped modify a fuel injection system for a mud-race-truck,
it's fuel cell holds enough fuel for 90 - 180 seconds
but you do not have time to read a gauge anyway.
If you can not burn the fuel up in 3 minutes you are going to be coming in
dead last anyway.
These guys really push those trucks hard.
Some use a Nitrous oxide tank combined with a "divers air tank"
to keep from pulling muddy water into the intake
and often run 30psi+ manifold pressure.

KF4HAZ - Lonnie

----- From: "Dave VanHorn" <dvanhorn@
> >
> >Right.  I suggested 100mHz = .1Hz low pass for the fuel and 1Hz low pass
for
> >oil pressure.  In other words, around 10 second response to fuel and 1
> >second response to oil pressure.
>
> If your fuel is changing faster than that, you have LARGE problems! :)

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2004\09\10@121311 by Dave VanHorn

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At 10:57 AM 9/10/2004, Falcon Wireless Tech Support - KF4HAZ wrote:

>Actually I have helped modify a fuel injection system for a mud-race-truck,
>it's fuel cell holds enough fuel for 90 - 180 seconds
> but you do not have time to read a gauge anyway.
>If you can not burn the fuel up in 3 minutes you are going to be coming in
>dead last anyway.
>These guys really push those trucks hard.
>Some use a Nitrous oxide tank combined with a "divers air tank"
>to keep from pulling muddy water into the intake
>and often run 30psi+ manifold pressure.

Like I said, in that case you have larger problems to worry about.
Pretty much, you would just need something to check that you're starting with a full tank.

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2004\09\10@123550 by Mike Hord

picon face
On Fri, 10 Sep 2004 09:55:59 -0500, Dave VanHorn <.....dvanhornKILLspamspam@spam@dvanhorn.org> wrote:
>
> >
> >Right.  I suggested 100mHz = .1Hz low pass for the fuel and 1Hz low pass for
> >oil pressure.  In other words, around 10 second response to fuel and 1
> >second response to oil pressure.
>
> If your fuel is changing faster than that, you have LARGE problems! :)

And knowing now versus knowing in 10 seconds is unlikely to give you
time enough to do anything constructive about it anyway.  ;-)

Mike H.
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2004\09\11@041136 by Peter L. Peres

picon face

On Fri, 10 Sep 2004, Olin Lathrop wrote:

> Gerhard Fiedler wrote:
>>> Again, assume that the wire coming in will have occasional short
>>> spikes of 200V and figure out what that will do.
>>
>> When you say "short spikes", do you have an idea what "short" means?
>> ns, us, ms range?
>
> I would want it to survive at 200V for a few 100uS.  You can assume the
> repition of these events are low so that the average power can be ignored,
> but the instantaneous spike must not damage anything.

'my' clamp with 2 pnp + 2 npn transistors ? How close does the input have
to get to the power rails and still not be distorted ? The clamp allows
you to go to within 50mV of each rail for reasonably low input impedance.

Peter
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2004\09\11@075934 by Howard Winter

face
flavicon
picon face
Olin,

On Fri, 10 Sep 2004 10:39:24 -0400, Olin Lathrop wrote:

{Quote hidden}

This fractional-Hertz thing is really hard on the grey matter - I made the same mistake as (I think) Russell
did - and you're right of course, 0.1Hz is ten seconds, not a tenth of a second!  :-)

But I agree with Russell that a 1-second response on an oil-pressure gauge is too slow - watching the needle
in the good old days could tell you a lot about the state of the engine and of the oil itself.  I had a Ford
Corsair (V4 2litre, early 70's vintage) which would show a much faster drop-to-zero on engine stop when the
oil was due for changing than otherwise, and this was probably a *difference* of only 0.1S, but which was
detectable by eye.

A 10-second response for fuel level on a road car is probably only going to matter when you're filling it up,  
unless you're driving one of those famous cars where the fuel tank had a tendency to drop off... :-)

I wonder if there's a market for an add-on fuel gauge corrector device using a PIC?  The gauge on my car is
reliable, but terribly non-linear, and it would be nice if half-full on it represented just that.

Cheers,


Howard Winter
St.Albans, England


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2004\09\11@080856 by Gerhard Fiedler

picon face
>> Imagine a 100n cap at the input (5 V, 8 bit, 20 mV/digit). It's about
>> 2000 times the ADC capacitor (50p), which means that charging the ADC
>> sampling cap to either end of the range doesn't change the total
>> voltage by more than 1/2000 of the maximum voltage difference, or < 3
>> mV. This seems negligible.
>
> Yes, for one sample.  You are really moving a fixed charge every time the
> input channel is sampled.  That charge times the sample frequency is a
> current.  That current times the source resistance is an offset voltage.

I did miss that effect. But OTOH, there's usually not much use in sampling
the channel more often than the frequency of the low pass formed by the
100n cap and the input resistor, in which case the current through the
input resistor would compensate the charge current from the sample cap.

> Note that the capacitor value doesn't enter into this equation as long as
> it's big enough to carry most of the accumulated charge from one sample to
> the next.  

It enters through the low pass formed by the input resistor and the
capacitor.

> Your logic above only holds when there is no "memory" from one
> sample to the next.

Which could also be achieved by sampling with a low enough frequency, as
stated above. I haven't calculated that limit, or simulated, but probably
will do either. Thanks for pointing this out.

Gerhard
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2004\09\11@081042 by Gerhard Fiedler

picon face
>>>> Again, assume that the wire coming in will have occasional short
>>>> spikes of 200V and figure out what that will do.
>>>
>>> When you say "short spikes", do you have an idea what "short" means?
>>> ns, us, ms range?
>>
>> I would want it to survive at 200V for a few 100uS.  You can assume the
>> repition of these events are low so that the average power can be ignored,
>> but the instantaneous spike must not damage anything.
>
> 'my' clamp with 2 pnp + 2 npn transistors ? How close does the input have
> to get to the power rails and still not be distorted ? The clamp allows
> you to go to within 50mV of each rail for reasonably low input impedance.

I'd say in most automotive analog sensor applications, 50 mV is close
enough. They usually don't reach the rails for usable input.

Gerhard
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2004\09\11@111406 by Russell McMahon

face
flavicon
face
> > Right.  I suggested 100mHz = .1Hz low pass for the fuel and 1Hz low pass
for
> > oil pressure.  In other words, around 10 second response to fuel and 1
> > second response to oil pressure.
>
> This fractional-Hertz thing is really hard on the grey matter - I made the
same mistake as (I think) Russell
> did -

What! Me make mistakes ??? !
Er, yes. I did.
Even after noting what Olin was doing i still stupidly got it wrong.
I do find such nomenclature less than useful, but I still shouldn't get it
wrong :-(
I also dislike mF for millifarads even though it is an "emgineering
standard" designation. It's not common enough to fit comfortably with many
people and cause errors.

> But I agree with Russell that a 1-second response on an oil-pressure gauge
is too slow - watching the needle
> in the good old days could tell you a lot about the state of the engine
and of the oil itself.  I had a Ford
> Corsair (V4 2litre, early 70's vintage) which would show a much faster
drop-to-zero on engine stop when the
> oil was due for changing than otherwise, and this was probably a
*difference* of only 0.1S, but which was
> detectable by eye.

I agree about the oil gauge response time for cases like yours, and the one
I mentioned. In my case the vehicle was a 2 litre Austin A70, 1950 vintage
:-). I haven't owned a vehicle with an oil pressure gauge for decades now.

> I wonder if there's a market for an add-on fuel gauge corrector device
using a PIC?  The gauge on my car is
> reliable, but terribly non-linear, and it would be nice if half-full on it
represented just that.

Worth a thought. Easily calibrated. Put constant increment amounts of fuel
in tank and tell processor after each input. A good question is, given the
state of modern electronics, why does anyone make non-linear fuel gauges.



       RM

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2004\09\11@120952 by olin_piclist

face picon face
Russell McMahon wrote:
> A good question is,
> given the state of modern electronics, why does anyone make
> non-linear fuel gauges.

Because you will (did) buy the car anyway?

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2004\09\11@133343 by Jan-Erik Soderholm

face picon face
Howard Winter wrote :

> I wonder if there's a market for an add-on fuel gauge
> corrector device using a PIC?  The gauge on my car is
> reliable, but terribly non-linear, and it would be nice if
> half-full on it represented just that.

Hi.
My car beeps and lits a symbol on the dashboard when there
is aprox 10 liters left, so I just stop the the pump station and
fill it up. I couldn't care less if half-full actualy is 40% or 60% :-)

There is a Swedish stand-up comedian that once said :

"Now, when I'm over 40, there isn't much excitment left in life. To at
least get *some* excitment, I usualy take an extra turn around the
block when the fule gauge is on red..." :-)

Regards,
Jan-Erik.
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2004\09\11@151007 by Gerhard Fiedler

picon face
> I also dislike mF for millifarads even though it is an "emgineering
> standard" designation. It's not common enough to fit comfortably with many
> people and cause errors.

I think the SI is highly underrated -- at least in some countries, and it
seems predominantly in English-speaking countries. But there is good
material about the SI in English; even good US government material (where
the SI is the legal standard :).

Gerhard
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2004\09\11@215724 by steve
flavicon
face
>  A good question is,
> given the state of modern electronics, why does anyone make non-linear
> fuel gauges.

The state of modern automotive electronics still means that the display
in the BA Falcon XR6 that says you have 24km range left, can have an
error of 25km. Grrr !

Steve.


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2004\09\12@001446 by hilip Stortz

picon face
go to national.com or other op amp maker and see how they suggest
protecting inputs, most of it applies to any input.  there are also
chips designed to do this that have series fets that limit the fault
current in addition to voltage clamping.  you should also always clamp
to the +5 or other supply rails, this also protects you when ground is lost.

"dr. Imre Bartfai" wrote:
>
> Hi,
>
> a can't see the point of the D2 unless u're using Schottky as for reverse
> voltage D1 is forward biased, too. However, I would suggest a voltage
> follower with an input resistor of some kohms and - better yet - a
> well-calculated antialiasing filter (e.g. Sallen-Key one). It's input
> could be protected with Zeners after the input resistor. I am not sure BTW
> Zeners are fast enough to cut short spikes.
--------

-- Philip Stortz--"In Germany they came first for the Communists, and I
didn't speak up because I wasn't a Communist. Then they came for the Jews, and I didn't speak up because I wasn't a
Jew. Then they came for the trade unionists, and I didn't speak up because I
wasn't a trade unionist. Then they came for the Catholics, and I didn't speak up because I was a
Protestant. Then they came for me, and by that time no one was left to speak up."
-- Martin Niemöller, 1892-1984 (German Lutheran Pastor), on the Nazi
Holocaust, Congressional Record 14th October 1968 p31636.



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2004\09\12@074555 by Howard Winter

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flavicon
picon face
On Sun, 12 Sep 2004 13:57:02 +1200, stevespamKILLspamtla.co.nz
wrote:

> The state of modern automotive electronics still means
that the display in the BA Falcon XR6 that says you have
24km range left, can have an error of 25km. Grrr !

Ah, the old "inappropriate resolution" problem!  :-)  
This tends to happen with digital displays - with a
needle readout gauge there's always the built in
resolution diluters of the width of the needle and the
markings, and parallax.  Putting a magnifying glass over
the fuel gauge so you can see *exactly* when it's empty
isn't something any sane manufacturer would do...

I have a GPS that gives (among other things) altitude to
a resolution of 1ft.  The best horizontal accuracy it
has ever claimed is 23ft, and vertical accuracy is
generally no better than half as good, so it's showing a
figure to 1ft resolution that has a possible error
getting on for 50ft!

"How many Vulcans does it take to change a lightbulb,
Mr.Spock?"  "Approximately 1.0000000000000000, Captain"

:-)

Cheers,


Howard Winter
St.Albans, England


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2004\09\12@145705 by M. Adam Davis

flavicon
face
Howard Winter wrote:

>Ah, the old "inappropriate resolution" problem!  :-)  
>This tends to happen with digital displays - with a
>needle readout gauge there's always the built in
>resolution diluters of the width of the needle and the
>markings, and parallax.  Putting a magnifying glass over
>the fuel gauge so you can see *exactly* when it's empty
>isn't something any sane manufacturer would do...
>  
>
Of course they don't.  Instead they use a deceptive scale - mine has
markings at each 1/4, but is the tank half empty when it points to the
1/2 mark?  No, it's closer to 1/3 full.  It appears that they use a
logarithmic type sensor with a linear display (or vice versa).  I
suppose they assume people want more resolution the closer to empty the
tank becomes, but for me I'd like to know that since I can go 240 miles
on one tank then I have 0, 60, 120, 180, 240 at each mark.

>I have a GPS that gives (among other things) altitude to
>a resolution of 1ft.  The best horizontal accuracy it
>has ever claimed is 23ft, and vertical accuracy is
>generally no better than half as good, so it's showing a
>figure to 1ft resolution that has a possible error
>getting on for 50ft!
>  
>
Well, you also must account for precision and repeatability (nevermind a
host of other factors).  It may not have a good accuracy, but if you
move it upwards 100 ft, then is it relatively accurate?  Absolute
accuracy is poor, but perhaps relative accuracy matches the resolution.

A device I'm building displays a tenth of a degree inclination, but due
to temperature variations is only absolutely accurate to +/- 1 degree.  
This application, however, only needs relative accuracy (zeroed each
use) and it provides a much greater relative accuracy.

>"How many Vulcans does it take to change a lightbulb,
>Mr.Spock?"  "Approximately 1.0000000000000000, Captain"
>  
>
Fortunately spock knew what his error was, else captian would have
sacked him.  ;-)

-Adam

>  
>
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2004\09\12@185558 by hilip Stortz

picon face
it comes from how they cheaply and simply implemented the fuel sensor. i forget what the typical circuit and mechanical arraignment are, but
that's where the nonlinearity comes from, i don't think anyone planed it
that way, they may have realized that's what would happen, but didn't
care given that it basically works (on a plane of course you need
absolute accuracy since running out is really bad and to save
weight/fuel they often don't put in much more than they need for the
planed trip).  the accuracy problems are also from cheap uncalibrated
sensors and equally cheap meters that aren't particularly calibrated
other than usually setting the full scale and/or empty (interestingly i
once had a former state patrol car, it ran out of gas with a 1/4 tank
still left!  seems they'd diddled with it to help if someone stole the
car, i.e. they'd keep driving away thinning they still had plenty of gas
and then run out early, a very clever idea i thought though learning it
the hard way was annoying).  it just happens to turn out that you get
more resolution and stronger feedback that you need gas soon towards the
end.  i have however seen cars with fairly linear and accurate fuel
gauges so you really want to know how they work in the particular model
you are driving, with many cars E means E, not hurry up and get gas
within 10-20 miles, it can be a rude surprise.

"M. Adam Davis" wrote:
------
> Of course they don't.  Instead they use a deceptive scale - mine has
> markings at each 1/4, but is the tank half empty when it points to the
> 1/2 mark?  No, it's closer to 1/3 full.  It appears that they use a
> logarithmic type sensor with a linear display (or vice versa).  I
> suppose they assume people want more resolution the closer to empty the
> tank becomes, but for me I'd like to know that since I can go 240 miles
> on one tank then I have 0, 60, 120, 180, 240 at each mark.
--------

-- Philip Stortz--"In Germany they came first for the Communists, and I
didn't speak up because I wasn't a Communist. Then they came for the Jews, and I didn't speak up because I wasn't a
Jew. Then they came for the trade unionists, and I didn't speak up because I
wasn't a trade unionist. Then they came for the Catholics, and I didn't speak up because I was a
Protestant. Then they came for me, and by that time no one was left to speak up."
-- Martin Niemöller, 1892-1984 (German Lutheran Pastor), on the Nazi
Holocaust, Congressional Record 14th October 1968 p31636.

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2004\09\12@234021 by M. Adam Davis

flavicon
face
I've always suspected it was because the sensor is an arm - little
response at the high end, heavy response at the low end.  Don't care
enough to fix it or even investigate it.

I'm just pleased that the cruise control increases by exacly one mph per
click on the set, and decrease by exactly 1mph per click on the cruise.  
Want to go 3mph faster?  click, click, click...

-Adam

Philip Stortz wrote:

{Quote hidden}

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2004\09\13@004448 by Russell McMahon

face
flavicon
face
> ... on a plane of course you need absolute accuracy since running out is
really bad ...


Google on "Gimli glider" and 767 for an interesting account :-)



       RM

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2004\09\13@051832 by hilip Stortz

picon face
i love millifarads and nanofarads.  i never liked micro-microfarads, as
picofarads were once called.  i greatly prefer proper engineering units
with the proper si prefixes.  it's odd the first time you see it, but
it's pretty easy to adjust to if you have done any physics work.  in any
case i greatly prefer it to part values that are less than 1 prefixed
unit, i.e. .001 microfarad rather than 1 nanofarad which seems much
nicer to me.  the last place i did electronics work i converted my boss
and the other electronics "engineer" to using the engineering prefixes. of course you often have to convert when looking parts up in catalogs
but that's not hard either.  i'd be so happy if we could chuck english
units, they really do make the math ugly when you get into complex
problems and it's a lot harder to carry the units through the
calculation which you should be able to do with a correct formula. hell, i think benjamin franklin even wanted to dump the english units
and go metric, instead we in the u.s. who do any technical work have to
learn both and convert constantly, other than when it's -40 degrees of
course ;).

Gerhard Fiedler wrote:
>
> > I also dislike mF for millifarads even though it is an "emgineering
> > standard" designation. It's not common enough to fit comfortably with many
> > people and cause errors.
>
> I think the SI is highly underrated -- at least in some countries, and it
> seems predominantly in English-speaking countries. But there is good
> material about the SI in English; even good US government material (where
> the SI is the legal standard :).
---------

-- Philip Stortz--"In Germany they came first for the Communists, and I
didn't speak up because I wasn't a Communist. Then they came for the Jews, and I didn't speak up because I wasn't a
Jew. Then they came for the trade unionists, and I didn't speak up because I
wasn't a trade unionist. Then they came for the Catholics, and I didn't speak up because I was a
Protestant. Then they came for me, and by that time no one was left to speak up."
-- Martin Niemöller, 1892-1984 (German Lutheran Pastor), on the Nazi
Holocaust, Congressional Record 14th October 1968 p31636.

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2004\09\13@064113 by Jan-Erik Soderholm

face picon face
Philip Stortz wrote :

> i love millifarads and nanofarads.  i never liked
> micro-microfarads, as picofarads were once called.

Hi.
I have never heard or seen "micro-micro-farad".
Do you have any reference ?

> i greatly prefer proper  engineering units
> with the proper si prefixes.

>From an SI perspective. it's not *wrong* to say
"10 000 microfarad" instead of "10 millifarad", is it ?

> i'd be so happy if we could chuck english units,...

But YES, but then we are not speaking about capacitors, right ?

> hell, i think benjamin franklin even wanted to dump the english units
> and go metric,...

Sure, the French was well on their way to get the US with them on
the metric project, but then they (the French) sent an ambassador to
the US that was, well, a bit to much "French", so to speak. :-)

The US president at the time get mad at him, and leaved the metric
project. And there we (or rather they, the US'ers) are with that
inch/feet/oz/lb/mph/gallon/whatever mess... :-)

Must be hard to be all alone in the whole big world beeing "different" :-)

Most standards are there for a reason. It's the same with, just to
take one right out-of-the-blue, writing rules telling you when to use
proper upper/lower case. It *could* be a readability thing... :-)


Best Regards,
Jan-Erik.
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2004\09\13@073837 by Russell McMahon

face
flavicon
face
> > > I also dislike mF for millifarads even though it is an "engineering
> > > standard" designation. It's not common enough to fit comfortably with
many
> > > people and cause errors.

> i greatly prefer proper engineering units
> with the proper si prefixes.  it's odd the first time you see it, but
> it's pretty easy to adjust to if you have done any physics work.

I have no trouble with "proper" units personally (at least most of the time
until I get tripped up my Olin's perfectly correct use of milli-Hz).

My point was what I said. It causes erros. It causes confusion. One can
argue standards and "correct" units and nomenclature as much as one likes.
And i agree that standards should be the norm. But there are occasions where
one should be aware that one's "correct" stand is liable to lead to
undesired outcomes. If this is acceptable then lay on.

The main problems with "milliFarad" are, I think the relative uncommon-ness
of values in this range and the use of a Greek character for "micro" which
encourages the use of the "m" prefix for micro. In eg ASCII text the only
(arguably) safe way for microFarad is uF - which is non standard. One may
attempt to use alternate character sets in email at one's peril.

* While popular usage is almost entirely against me, I'm unsure that eg
millifarad should be correct.
The fundamental unit is, of course, the Farad and should be capitalised when
written as it was named after Faraday. Similarly Amp, Ohm, Erlang, Volt,
Kelvin etc. But not, of course,  eg second, minute, metre, foot, pound,
kilogram.
So, while millisecond is permissible I suspect we should have milliFarad or
milli-Farad (or even milli Farad).

> ...  instead we in the u.s. who do any technical work have to
>  learn both and convert constantly, other than when it's
> -40 degrees of course ;).

Kelvin ? :-)


       RM









 in any
{Quote hidden}

many
> > > people and cause errors.
> >
> > I think the SI is highly underrated -- at least in some countries, and
it
> > seems predominantly in English-speaking countries. But there is good
> > material about the SI in English; even good US government material
(where
{Quote hidden}

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2004\09\13@074918 by Russell McMahon

face
flavicon
face
> > micro-microfarads, as picofarads were once called.

> I have never heard or seen "micro-micro-farad".
> Do you have any reference ?

micro micro Farad or uuF (or even mmf !) was the standard term in the days
of valve / steam powered radio.
I grew up with micro micro farad :-)

Google produces 37 hits.


       RM


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2004\09\13@081237 by Gerhard Fiedler

picon face
> i greatly prefer proper engineering units with the proper si prefixes.
> it's odd the first time you see it, but it's pretty easy to adjust to if
> you have done any physics work.  

When I started with electronics, that's how I learned it. It seems so
obvious and natural. And I didn't have to re-learn anything when I got
deeper into physics. Gladly electronics is, even in the USA, very much
"metric" already, being a rather new field of technology.

> in any case i greatly prefer it to part values that are less than 1
> prefixed unit, i.e. .001 microfarad rather than 1 nanofarad which seems
> much nicer to me.  

Oh yes, and especially on faxes or other bad copies...

> i'd be so happy if we could chuck english units, they really do make the
> math ugly when you get into complex problems and it's a lot harder to
> carry the units through the calculation which you should be able to do
> with a correct formula.

This thing with the units is the real beauty of the SI. I think that
whoever "tasted" this once on any interdisciplinary problem wouldn't want
to miss it again. It's not only about carrying the units through the
calculation (a very good double-check whether your calculation makes sense,
and which rarely works with the English units). It's also about using
always the same units for the same physical entity, like power or energy,
independently of the problem domain. It's very relaxing being able to talk
to energy and mechanical engineers in kW (and not in BTUs and whatnot :)

> hell, i think benjamin franklin even wanted to dump the english units
> and go metric, instead we in the u.s. who do any technical work have to
> learn both and convert constantly, other than when it's -40 degrees of
> course ;).

Whoever wants to read about the legal standard of measurements in the USA
(in 75 a goal was set to put all public organizations on metric by 92 --
not for any arbitrary reason, but because going metric would save the US
industry a bundle in the long run and would increase its competitiveness on
the international markets), and a good guide about how to properly use the
SI, can peruse this paper: physics.nist.gov/Pubs/SP811/contents.html
or this page http://physics.nist.gov/cuu/Units/index.html

Gerhard
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2004\09\13@082145 by Gerhard Fiedler

picon face
> hell, i think benjamin franklin even wanted to dump the english units
> and go metric, instead we in the u.s. who do any technical work have to
> learn both and convert constantly, other than when it's -40 degrees of
> course ;).

http://www.wadenelson.com/gimli.html (contributed by Russell)

How many incidents like this one (and the Mars thingy) does it need? :)
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2004\09\13@083718 by Ake Hedman

flavicon
face
Russell McMahon wrote:

>>>micro-microfarads, as picofarads were once called.
>
[PIC] Protecting PIC A/D inputs.... hmmmm ;-) time to change the TAG.....

/Ake

--   ---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org

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2004\09\13@093449 by Bob Ammerman

picon face
> > hell, i think benjamin franklin even wanted to dump the english units
> > and go metric, instead we in the u.s. who do any technical work have to
> > learn both and convert constantly, other than when it's -40 degrees of
> > course ;).

Or zero of just about any other unit. (ie: 0 feet = 0 meters, etc).

;)

Bob Ammerman
RAm Systems
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2004\09\13@142449 by Peter L. Peres

picon face

On Mon, 13 Sep 2004, Russell McMahon wrote:

>>> micro-microfarads, as picofarads were once called.
>
>> I have never heard or seen "micro-micro-farad".
>> Do you have any reference ?
>
> micro micro Farad or uuF (or even mmf !) was the standard term in the days
> of valve / steam powered radio.
> I grew up with micro micro farad :-)

So what's a cm ? 0.82 pF ?

Peter
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2004\09\13@151235 by DJMurray

flavicon
face
Well, Phillip, I can't address anything but what I've personnally
experienced.  I had a Ford pickup truck that was also "uncalibrated" as
far as the fuel gauge was concerned.

Late 70's and early 80 Ford pickups used a fuel sensor that had an arm
with a float on the end.  The pivot point was a wirewound rheostat with
the least resistance when the tank was full (the arm was primarily
horizontal at FULL).  As the fuel went down, so did the arm, until the
EMPTY position was reached as the arm neared vertical.  I know this,
since I've personally replaced one and "fixed" another when I couldn't
get a replacement at a reasonable cost.

Now, I do NOT believe FORD used a non-linear wirewound rheostat,
although I didn't check it's linearity.  Assuming it was linear, the arm
would nominally be at a 45 degree angle to INDICATE 1/2 full on the
gauge, which, if you remember Trig, translates to 0.707 times the total
vertical travel distance of the arm.  If this is correct, this means the
tank is over 2/3 empty by the time the gauge reads HALF!!

All this assumes linearity - both of the rheostat and the gauge.  Never
having calibrated either, I am making the assumption that they are
linear, since the results of my truck seem consistent with the theory
just proposed.

Does any of this seem to make sense??
Dennis



Philip Stortz wrote:

{Quote hidden}

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2004\09\13@200713 by hilip Stortz

picon face
yeah, cm is a bastard child, as are all units derived from it like
angstroms, now replaced my nanometers in more civilized circles though
still encountered on occasion.  i'd have to look up what's after pico, i
think it's atto and then femto, but i don't have that handy either, my
newer crc handbook is still to be unpacked.  i'd definitely have to check.

"Peter L. Peres" wrote:
-----
>
> So what's a cm ? 0.82 pF ?
-----

-- Philip Stortz--"In Germany they came first for the Communists, and I
didn't speak up because I wasn't a Communist. Then they came for the Jews, and I didn't speak up because I wasn't a
Jew. Then they came for the trade unionists, and I didn't speak up because I
wasn't a trade unionist. Then they came for the Catholics, and I didn't speak up because I was a
Protestant. Then they came for me, and by that time no one was left to speak up."
-- Martin Niemöller, 1892-1984 (German Lutheran Pastor), on the Nazi
Holocaust, Congressional Record 14th October 1968 p31636.

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2004\09\13@202912 by hilip Stortz

picon face
the type of fuel gauge you describe is i believe how most of them have
worked traditionally, doubtless the trig is a large part of the
nonlinearity.  i had forgotten that the trig was part of it when i
pictured it in my mind, for some reason i thought half full would be
half of the total rotation.  just one of the hazards of thought
experiments, like any simulation mistakes can be made.  i'm sure
nonlinearity of the rheostat and the gauge also have some effect, though
it's probably largely swamped by the trig involved.  
i know making good linear analog movements is not trivial, and for the
better ones specific scales are fitted to them that match the
particularly meter closely, i.e. they make up a number of scales with
various degrees of the common distortions away from linearity and use a
scale that most closely matches a particular movement.  my dad worked on
such precision gear at one time, before i was born and i'm fortunate to
have some of that knowledge.  
like all just starting to learn there was a time when i just assumed
analog movements were very linear and easy to make, experience shows
that it's a little more difficult to approach the ideal.  that's also
where i learned that soapy water is good for making plastic antistatic
as they had to use it on meter faces to reduce the attraction between
the pointer and the meter face on plastic faced meters and i think the
glass faced as well.

DJMurray wrote:
{Quote hidden}

-------

-- Philip Stortz--"In Germany they came first for the Communists, and I
didn't speak up because I wasn't a Communist. Then they came for the Jews, and I didn't speak up because I wasn't a
Jew. Then they came for the trade unionists, and I didn't speak up because I
wasn't a trade unionist. Then they came for the Catholics, and I didn't speak up because I was a
Protestant. Then they came for me, and by that time no one was left to speak up."
-- Martin Niemöller, 1892-1984 (German Lutheran Pastor), on the Nazi
Holocaust, Congressional Record 14th October 1968 p31636.


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2004\09\14@065521 by Gerhard Fiedler

picon face
> * While popular usage is almost entirely against me, I'm unsure that eg
> millifarad should be correct.
> The fundamental unit is, of course, the Farad and should be capitalised when
> written as it was named after Faraday. Similarly Amp, Ohm, Erlang, Volt,
> Kelvin etc. But not, of course,  eg second, minute, metre, foot, pound,
> kilogram.
> So, while millisecond is permissible I suspect we should have milliFarad or
> milli-Farad (or even milli Farad).

The NIST suggests to use the unit abbreviations (with they proper
capitalization, of course) in technical and scientific texts, for clarity.

But in an example, they also write "60 watts" with a lower case first
letter... even though that should be, according to you, "60 Watt" (or "60
Watts"?). But then, the NIST is in the USA :)  I guess they're right about
that it's better to use the correct unit abbreviations.

One interesting thing is their suggestion to drop ppm etc, especially ppb.
Instead of these they suggest something like (uA/A), which adds some
information that ppm doesn't have. And the specific problem with ppb is
that "billion" is quite an ambiguous expression.

Gerhard
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2004\09\14@082424 by Russell McMahon

face
flavicon
face
> The NIST suggests to use the unit abbreviations (with they proper
> capitalization, of course) in technical and scientific texts, for clarity.

> But in an example, they also write "60 watts" with a lower case first
> letter... even though that should be, according to you, "60 Watt" (or "60
> Watts"?). But then, the NIST is in the USA :)  I guess they're right about
> that it's better to use the correct unit abbreviations.

The convention is that units which are named after a person have their first
letter capitalised.
Most unit names are unique so failure to capitalise will usually not cause
errors.

Correct capitalisation often leads to strange appearance.

   km, m/s, Ws, kWh, MWh, mWh (which would be unusual), mAh, Nm, Nm/s, kPa
(two letters in unit name), kPa/m^2 ...

Failure to correctly capitalise the multiplier can lead to error - but often
not one that will easily be over looked.

1 mF = 0.001 Farad
1 MF = 1,000,000 Farad :-)


   RM




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2004\09\14@085252 by Jan-Erik Soderholm

face picon face
Russell McMahon wrote :

> Correct capitalisation often leads to strange appearance.
>
> km, m/s, Ws, kWh, MWh, mWh (which would be unusual), mAh,
> Nm, Nm/s, kPa (two letters in unit name), kPa/m^2 ...

Hi.
I don't know, but I can't see anything strange here.
They are exactly as I'm used to see them...

Jan-Erik.

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2004\09\14@102437 by Howard Winter

face
flavicon
picon face
On Mon, 13 Sep 2004 23:38:26 +1200, Russell McMahon wrote:

>...<

> The fundamental unit is, of course, the Farad and should be capitalised when
> written as it was named after Faraday. Similarly Amp, Ohm, Erlang, Volt,
> Kelvin etc. But not, of course,  eg second, minute, metre, foot, pound,
> kilogram.

I think you mean "gram" :-)

> So, while millisecond is permissible I suspect we should have milliFarad or
> milli-Farad (or even milli Farad).
>
>  > ...  instead we in the u.s. who do any technical work have to
> >  learn both and convert constantly, other than when it's
> > -40 degrees of course ;).
>
> Kelvin ? :-)

Bring back Rankine, I say (that's the temperature scale which starts with 0 at ablolute zero, and has degrees
the same size as Farehheit)!

"You learn something new every day" item for today:  "Byte" is spelled with a "y" so that a single typing
error (omitting or adding the "e" by mistake) would not give a valid but wrong alternative, so byt and bite
would be easy to spot as errors.  Foresight unusual in those setting standards!  :-)  It's just a shame that
milli and micro have the same initial letters...

Cheers,

Howard Winter
St.Albans, England


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2004\09\14@110113 by Support - KF4HAZ

flavicon
face
One easy trick is to use m for milli and µ for micro,
to type the mu "µ"- hold [ALT} and type 0181 on the numeric keypad.

KF4HAZ - Lonnie

<snip>
> "You learn something new every day" item for today:  "Byte" is spelled
with a "y" so that a single typing
> error (omitting or adding the "e" by mistake) would not give a valid but
wrong alternative, so byt and bite
> would be easy to spot as errors.  Foresight unusual in those setting
standards!  :-)  It's just a shame that
> milli and micro have the same initial letters...
>
> Cheers,
>
> Howard Winter
> St.Albans, England

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2004\09\14@113218 by Howard Winter

face
flavicon
picon face
On Tue, 14 Sep 2004 10:02:02 -0500, Falcon Wireless Tech Support - KF4HAZ wrote:

> One easy trick is to use m for milli and   for micro,
>  to type the mu " "- hold [ALT} and type 0181 on the numeric keypad.

That may be an easy way to type it, but not everyone will be able to read it!  The two places that I think you
typed the mu character are blank at this end.  I don't know where it went astray, but it doesn't actually
matter - the point is you can't assume that it will travel.

As a matter of interest, does the following character between the quotes: " " show as the "Euro" symbol for
others?

Cheers,


Howard Winter
St.Albans, England



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2004\09\14@115420 by hael Rigby-Jones

picon face


{Quote hidden}

No. I guess this is a disadvantage of plain text encoding.

Mike

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2004\09\14@125807 by Herbert Graf

flavicon
face
On Tue, 2004-09-14 at 11:02, Falcon Wireless Tech Support - KF4HAZ
wrote:
> One easy trick is to use m for milli and &#181; for micro,
>  to type the mu "&#181;"- hold [ALT} and type 0181 on the numeric keypad.
>
> KF4HAZ - Lonnie

Which is fine if the person reading your message is using the same font
as you are, or using another font that happens to map 181 to the mu
character. If you are using windows open up the character map and have a
look and see how often this is the case... hint, it's not much.

ASCII does NOT cover the mu character, therefore MANY fonts don't have
it, or have it in a different spot. There is NO standard that is
followed universally when it comes to this sort of thing.

The wisest course of action IMHO is to use u, with a note following it's
first usage (i.e. 300uF (micro-Farads)). TTYL

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2004\09\14@125838 by Carey Fisher - NCS

face picon face
  > "You learn something new every day" item for today:  "Byte" is
  > spelled with a "y" so that a single typing
  > error (omitting or adding the "e" by mistake) would not give a
  > valid but wrong alternative, so byt and bite
  > would be easy to spot as errors.  
  > Howard Winter
  > St.Albans, England
  >
 
BS
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2004\09\14@133151 by Jan-Erik Soderholm

face picon face
Falcon Wireless Tech Support - KF4HAZ wrote :

> One easy trick is to use m for milli and µ for micro,
>  to type the mu "µ"- hold [ALT} and type 0181 on the numeric keypad.

How do you do that on a Mac or a SUN workstation ?

Just use a lower case "u". That usualy works better
on a large number of mail platforms.

Jan-Erik.
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2004\09\14@144638 by Support - KF4HAZ

flavicon
face
Guess we will have to stick to m for milli and u for micro in plain text/7
bit situations
µf Works for Web pages.

KF4HAZ - Lonnie

----- From: "Herbert Graf" <mailinglist2@

{Quote hidden}

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2004\09\14@150431 by Peter L. Peres

picon face
part 1 325 bytes content-type:TEXT/PLAIN; charset=iso-8859-1; format=flowed (decoded quoted-printable)


On Tue, 14 Sep 2004, Falcon Wireless Tech Support - KF4HAZ wrote:

> One easy trick is to use m for milli and for micro,
> to type the mu ""- hold [ALT} and type 0181 on the numeric keypad.

I am impressed. That even shows up as mu in my X11 display.

Peter

part 2 194 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

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2004\09\14@154842 by Herbert Graf

flavicon
face
On Tue, 2004-09-14 at 14:47, Falcon Wireless Tech Support - KF4HAZ
wrote:
> Guess we will have to stick to m for milli and u for micro in plain text/7
> bit situations
> &#181;f Works for Web pages.
>
> KF4HAZ - Lonnie

Maybe for your browser it "works fine", but NOT for everybody. Some
browsers allow for html to specify which font is to be used, but even
that is dependant on that font being available on the host system.
Otherwise you are at the mercy of what default font the person reading
you page has, which often doesn't include mu in the same spot as you
think.

About the ONLY way I can think of getting around this problem
universally is to have the mu symbol as an image, that way as long as
the browser supports images it'll come out as a mu. But even THAT won't
work with non graphical web browsers (i.e. lynx). TTYL
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2004\09\14@174410 by olin_piclist

face picon face
Howard Winter wrote:
> As a matter of interest, does the following character between the
> quotes: " " show as the "Euro" symbol for others?

Nope.  Looks like a blank here.  Once again, the only true standard is
ASCII.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
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2004\09\14@195810 by Russell McMahon

face
flavicon
face
> As a matter of interest, does the following character between the quotes:
" " show as the "Euro" symbol for
> others?

No - it's a blank for me.
And it's a $20 character - a genuine space.
So something in the email pipeline has wiped it out completely.


                                RM

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2004\09\15@064436 by Russell McMahon

face
flavicon
face
> > &#181;f Works for Web pages.

Now that's very interesting.
The original "&#181;" that someone posted turned into a space ($20) in my
browser.

BUT the &#181; used above in uF (and which I copied here) displays as a &#181; for me.

If you cant see three "mu's" above then it doesn't work for you ;-)

Is there anyone who CAN'T see a mu between the following pair of quotation
marks ? => "&#181;"


       Russell McMahon

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2004\09\15@072038 by Jan-Erik Soderholm

face picon face
Mu mu !
("mu" is the sound of cows in Swedish... :-) )

Anyway...

Russell McMahon wrote :

> BUT the µ used above in uF (and which I copied here) displays
> as a µ for me.

I've checked your (this) mail a bit in detail...

In the header there are :

 Content-Type: text/plain;
         charset="UTF-8"
 Content-Transfer-Encoding: quoted-printable

and in the body of the mail I see :

  "BUT the = C2 = B5 used above in uF (and which I copied here)
   displays as a = C2 = B5 for me."

So the "mu" character gets "quoted" into the sequence "= C2 = B5",
which is all plain ASCII of course (quite natural, since SMTP can only
send 7-bit ASCII anyway without special coding...).

Then it's up to the actual mail tool to interpret and display this in
the "right" way.

Now, there was an earlier post where the "mu" was replaced
with a space. That might have happend at the sending end...

Note that I've added three spaces in the "= C2 = B5" string so
it will display that way in *our* mail tool. :-)

Jan-Erik.
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2004\09\15@081909 by Russell McMahon

face
flavicon
face
Even more interesting.

The trip to Howard and back destroyed the mu's (cows moo here :-) )
BUT the trip to Jan-Erik and back hasn't (for me).
I still see a mu here

> > BUT the µ used above in uF

= But the * used above in uF

   substituting * for the actual Greek character.



       RM 9


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2004\09\15@082656 by Andrew Warren

flavicon
face
Russell McMahon <piclistspamspam_OUTmit.edu> wrote:

> Is there anyone who CAN'T see a mu between the following pair of
> quotation marks ? => "µ"

   Yeah.  I see a two-character pair: an "A" with a circumflex over it,
   followed by a "mu".

   -Andy, who vaguely remembers having this conversation only a few
   weeks ago on the list...
=== Andrew Warren - @spam@aiwKILLspamspamcypress.com
=== === Principal Design Engineer
=== Cypress Semiconductor Corporation



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2004\09\15@083752 by Gerhard Fiedler

picon face
>> But in an example, they also write "60 watts" with a lower case first
>> letter... even though that should be, according to you, "60 Watt" (or "60
>> Watts"?).
> The convention is that units which are named after a person have their first
> letter capitalised.

It seems you are pretty alone with that convention. I did a Google search
for "unit capitalization watt volt", and came up with a number of links
about units, nothing (from a quick look through them) really definitive in
terms of a standard, but a few that seem quite serious, and they /all/
write units -- when spelled out -- with lower case (except Celsius and
Fahrenheit, but there the unit itself is "degree" and that is lower case
also).
Also the Wikipedia seems to spell units with lower case:
http://en.wikipedia.org/wiki/SI

> Correct capitalisation often leads to strange appearance.
>
>     km, m/s, Ws, kWh, MWh, mWh (which would be unusual), mAh, Nm, Nm/s, kPa
> (two letters in unit name), kPa/m^2 ...

That depends... since I've never seen it differently until I went to the
USA, neither in the amateur electronics literature with which I started in
the 60ies, nor in school or later university, nor in commercial
correspondence (like electricity bills), this doesn't look strange to me at
all.

"Strange appearance" to me is "ma" or "MA" for milliampere... :)

> Failure to correctly capitalise the multiplier can lead to error - but often
> not one that will easily be over looked.
Often the problem is not exactly overlooking it, the problem is seeing it,
and assuming what it should mean. And assuming wrong...

> 1 mF = 0.001 Farad
> 1 MF = 1,000,000 Farad :-)

More in our common range is mOhm vs MOhm... (which is the other case where
the standard calls for a greek letter).

Just checking how things work out here:
Ω - Unicode capital omega (as in mΩ milliohm or MΩ megohm)
μ - Unicode lower case mu
µ - ANSI micro sign

Gerhard

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2004\09\15@085022 by Gerhard Fiedler

picon face
>> µf Works for Web pages.

> Maybe for your browser it "works fine", but NOT for everybody. Some
> browsers allow for html to specify which font is to be used, but even
> that is dependant on that font being available on the host system.
> Otherwise you are at the mercy of what default font the person reading
> you page has, which often doesn't include mu in the same spot as you
> think.

This is not completely true. The web has this kind of thing pretty nicely
standardized. (Email has, too, but many seem to be reluctant to use
software that supports more recent -- say the last 10 years -- standards...
:) Of course you are free to use a non-standard browser, but then you are
really on your own and shouldn't be surprised about anything. (PIC Assembly
as client side script language is not impossible, but there will be few
sites -- besides your own -- that will work with that... :)

The named entity &micro; is well supported since pre-HTML4 times in most
browsers (anybody knows one that doesn't?), and as a named entity it is
independent of any specific font selection.

Gerhard

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2004\09\15@090608 by Gerhard Fiedler

picon face
> Which is fine if the person reading your message is using the same font
> as you are

The font is not the issue. The important things are encoded in the headers
of the email:

Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

(from Lonnie's original message).

It says which character set is is using -- and that /is/ a standard (and a
pretty commonly used one at that) --, and it says how this 8 bit character
set is encoded into 7 bit -- and that is also a (pretty commonly used)
standard.

The raw text looks like this:
"One easy trick is to use m for milli and =B5 for micro,
to type the mu "=B5"- hold [ALT} and type 0181 on the numeric keypad."

There's nothing non-ASCII in there. The =B5 is the quoted-printable
encoding for that character in the ISO-8859-1 font. This is such a common
standard font that any email software should have at least a translation
table for it.

It's up to the email processing software to be compliant with email
standards and decode and display such a message correctly, with whatever
font it uses. Some have trouble with email standards, but most don't.


The problem with Howard's message is this:

Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 8bit

His email software assumes an 8 bit transmission path (which obviously
wasn't given), Lonnie's email software doesn't.

Gerhard
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2004\09\15@091658 by Gerhard Fiedler

picon face
>> One easy trick is to use m for milli and µ for micro,
>>  to type the mu "µ"- hold [ALT} and type 0181 on the numeric keypad.
>
> How do you do that on a Mac or a SUN workstation ?

There must be a way to use Unicode or common ISO fonts on a Mac or SUN system. Otherwise, I'd say they are about 10 years behind the curve...

You better get used to international standards soon... China is on the way to being a world power, and if one thing is sure, it is that they will /not/ use 7 bit ASCII :)  (Not speaking of the fact that most outside the USA don't use 7 bit ASCII today.)

Gerhard

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2004\09\15@101106 by Support - KF4HAZ

flavicon
face
Must be on the senders email client as some of the senders reach some of the
receivers.
Or it may have something to do with the senders font settings.

KF4HAZ - Lonnie

----- From: "Russell McMahon" <apptech@

> > As a matter of interest, does the following character between the
quotes:
> " " show as the "Euro" symbol for
> > others?
>
> No - it's a blank for me.
> And it's a $20 character - a genuine space.
> So something in the email pipeline has wiped it out completely.
>
>
>                                  RM

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2004\09\15@103806 by Support - KF4HAZ

flavicon
face
Bravo Gerhard, now lets see if we can decipher the TAP protocol ;-)
Obviously if you get a large enough group of µcontroller programmers
together they will figure out how a particular communication protocol works,
and why it sometimes does not.

KF4HAZ - Lonnie

----- From: "Gerhard Fiedler" <lists@

{Quote hidden}

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2004\09\15@112142 by Shawn Wilton

flavicon
face
I don't wish to be a hard ass, but can you guys please changes the tags
to OT?
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2004\09\15@132758 by Howard Winter

face
flavicon
picon face
Gerhard,

On Wed, 15 Sep 2004 10:06:05 -0300, Gerhard Fiedler wrote:

> The problem with Howard's message is this:
>
> Content-Type: text/plain; charset="iso-8859-1"
> Content-Transfer-Encoding: 8bit
>
> His email software assumes an 8 bit transmission path (which obviously wasn't given),

Actually, not guilty!  I have my software set to the character set as shown, but "Quoted Printable" as the
encoding format.  If it arrived set to 8-bit, then something on the way has changed it...

...and in fact I just checked my reply to Russell as it left me (in this thread which I renamed "[OT]
Character sets") and it has this:

Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

When I received it back from the list, it had:

Content-Type: text/plain; charset="iso-8859-1"
X-Scanned-By: MIMEDefang 2.42
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from quoted-printable to 8bit by pch.mit.edu id
       i8FBQ0WM017884

So pch.mit.edu (Mailman?) is the culprit!  Nice of it to confess...  :-)

Cheers,


Howard Winter
St.Albans, England


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2004\09\15@171656 by Robert Monsen

picon face
The Art of Electronics, 2nd Edition, indicates that unit names are not capitalized when spelled out and used with a prefix, only when abbreviated. "Thus: hertz and kilohertz, but  Hz and kHz; watt, milliwatt, and megawatt, but W, mW, and MW". tera, giga, and mega are capitalized (T, G, and M) whereas kilo, milli, micro, nano, pico, and femto are not. Thus, MW is different from mW (except in spice, where the case is insignificant !)

Here is this NIST page describing unit usage, which appears to agree with the above:

http://physics.nist.gov/cuu/Units/units.html

Regards,
Bob Monsen

{Original Message removed}

2004\09\15@172234 by Russell McMahon

face
flavicon
face
> > The convention is that units which are named after a person have their
first
> > letter capitalised.

> It seems you are pretty alone with that convention.

It seems you are right.
But it seems I am right too ! :-)
(We both win (or lose)).

eg From the reasonably prestigious  http://www.sae.org we get an SI
standards paper which rigorously follows the nomenclature I mentioned. This
doesn't mean it is CORRECT or even standardised - just recognised and used
by (some) professional organisations who rigorously apply a rule set to
their publications. This is principally a document which rigorously
decsribes the usage of SI units in SAE publications. It takes the
capitalisation of abbreviations for units which are based on proper names as
a given without comment.

   http://www.sae.org/standardsdev/aerospace/parte.pdf

Suimilarly, this IEE Inspec 'Numerical data Indexing Thesaurus" agrees


http://www.iee.org/publish/support/inspec/document/ChemNum/ndithes.pdf

However, the majority of informally controlled usage does not use this
standard :-(

Note that when the full name of the unit is used it is in lower case, even
wnehna proper name.
eg 1.3 A    1.3 ampere.    6.4 V    6.4 volt



       RM



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2004\09\15@175426 by Shawn Wilton

flavicon
face
Will you PLEASE change the tags already.  This is NOT pic related.



{Quote hidden}

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2004\09\15@201428 by William Chops Westfield

face picon face
On Sep 15, 2004, at 6:06 AM, Gerhard Fiedler wrote:

> There's nothing non-ASCII in there. The =B5 is the quoted-printable
> encoding for that character in the ISO-8859-1 font. This is such a
> common
> standard font that any email software should have at least a
> translation
> table for it.
>
Yah, sure.  It showed up consistantly in your email as "equals B 5"
8bit characters are not in ascii, and not promised to make it through
smtp or other mail programs...

BillW

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2004\09\15@220336 by Wesley Moore

flavicon
face
Unicode is a standard encoding on OS X. It has system wide support.
http://www.apple.com/macosx/features/international/

WM

On Wed, Sep 15, 2004 at 10:16:52AM -0300, Gerhard Fiedler wrote:
{Quote hidden}

-- Wesley Moore - KILLspamwmooreKILLspamspamfreeshell.org - http://wmoore.no-ip.info/
Free Email provided by: SDF Public Access UNIX System http://sdf.lonestar.org/
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2004\09\16@073117 by Peter L. Peres

picon face
part 1 1614 bytes content-type:TEXT/PLAIN; charset=UTF-8; format=flowed (decoded quoted-printable)


On Tue, 14 Sep 2004, Herbert Graf wrote:

{Quote hidden}

Fyi the original message showed a correct mu character on my X11 display, but your quote of it changed it to a dichar: "A-circumflex" followed by the "mu" character (this is what I see in the first paragraph quoted above, between the quotes)

I aggree thta it's best to send only ascii characters. Special characters can be represented in many ways, f.ex. using html &name; entities or TeX-like "\mu \kappa \eta " etc. Sending non-human-readable codes is probably a bad idea because they could be rendered differently or not at all at the reciving end.

Peter

part 2 194 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

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2004\09\16@073619 by Peter L. Peres

picon face
part 1 711 bytes content-type:TEXT/PLAIN; charset=X-UNKNOWN; format=flowed (decoded quoted-printable)


On Tue, 14 Sep 2004, Jan-Erik Soderholm wrote:

> Falcon Wireless Tech Support - KF4HAZ wrote :
>
>> One easy trick is to use m for milli and for micro,
>>  to type the mu ""- hold [ALT} and type 0181 on the numeric keypad.

Fyi, this quote shows a single mu character between the quotes, unlike the other quote sent by someone else I commented on in a previous email.

> How do you do that on a Mac or a SUN workstation ?

On *nix you load a suitable keyboard map and it exists as a key o you use a utility not unlike 'character map' in windows and cut & paste. You also need to use a suitable font while doing this.

Peter

part 2 194 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

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2004\09\16@091708 by Peter L. Peres

picon face
part 1 632 bytes content-type:TEXT/PLAIN; charset=UTF-8; format=flowed (decoded quoted-printable)



On Wed, 15 Sep 2004, Russell McMahon wrote:

{Quote hidden}

I see a mu preceded by a A-circumflex

Peter

part 2 194 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

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2004\09\16@160153 by Gerhard Fiedler

picon face
>>>> µf Works for Web pages.
>>
>> Now that's very interesting.
>> The original "µ" that someone posted turned into a space ($20) in my
>> browser.
>>
>> BUT the µ used above in uF (and which I copied here) displays as a µ for me.
>>
>> If you cant see three "mu's" above then it doesn't work for you ;-)
>>
>> Is there anyone who CAN'T see a mu between the following pair of quotation
>> marks ? => "µ"
>
> I see a mu preceded by a A-circumflex
>
> Peter

In finding out whether it's your client or something in the transmission
path, it's a good thing to look at the message source. What I received from
you, looks like this (slightly snipped):
-----------------------------
Content-Type: TEXT/PLAIN; charset=UTF-8; format=flowed
Content-Transfer-Encoding: QUOTED-PRINTABLE

>>> =C2=B5f Works for Web pages.
>
> Now that's very interesting.
> The original "=C2=B5" that someone posted turned into a space ($20) in my
> browser.

> Is there anyone who CAN'T see a mu between the following pair of quotatio=
n
> marks ? =3D> "=C2=B5"

I see a mu preceded by a A-circumflex
-----------------------------

The message is in UTF-8. UTF-8 encodes several characters in more than one
byte. For example, the B5 character that's the mu in the original (and very
common ISO-8859-1 character set, would be encoded as C2B5 in UTF-8.
When I look at what comes from you, this is all correct (and my email
program shows it as a single mu). The message header shows that it is UTF-8
encoded as quoted-printable, and in the body source I see the =C2=B5
sequence, which is the quoted-printable encoding of the C2B5 character,
which again in UTF-8 is the encoding of the Unicode character B5, which is
the lower case mu.

However, if your program doesn't know how to deal with UTF-8 and interprets
the message as if it was ISO-8859-1 (or something similar), then it would
in fact see two characters, C2 and B5 -- which happen to be A-circumflex
and mu in ISO-8859-1.

This seems to indicate that your email program can't read UTF-8 properly.
You could verify this by looking at the message source and check whether
what I describe above is what you see locally (I only see what I receive
from you, which may or may not be what you have there).

Gerhard



PS UTF-8 is here: http://www.ietf.org/rfc/rfc3629.txt

  The table below summarizes the format of these different octet types.
  The letter x indicates bits available for encoding bits of the
  character number.

  Char. number range  |        UTF-8 octet sequence
     (hexadecimal)    |              (binary)
  --------------------+---------------------------------------------
  0000 0000-0000 007F | 0xxxxxxx
  0000 0080-0000 07FF | 110xxxxx 10xxxxxx
  0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
  0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

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2004\09\16@160754 by Gerhard Fiedler

picon face
>>> One easy trick is to use m for milli and µ for micro,
>>>  to type the mu "µ"- hold [ALT} and type 0181 on the numeric keypad.
>
> Fyi, this quote shows a single mu character between the quotes, unlike the
> other quote sent by someone else I commented on in a previous email.

Again, a look at the raw source reveals this (slightly snipped):
------------------------
Content-Type: TEXT/PLAIN; charset=X-UNKNOWN; format=flowed
Content-Transfer-Encoding: QUOTED-PRINTABLE

>> One easy trick is to use m for milli and =B5 for micro,
>>  to type the mu "=B5"- hold [ALT} and type 0181 on the numeric keypad.

Fyi, this quote shows a single mu character between the quotes, unlike
the=
=20
other quote sent by someone else I commented on in a previous email.
------------------------

No character set defined, but the source encoded as something similar to
ISO-8859-1 -- where the mu character is a single byte B5. This is
consistent with what I wrote to you in this thread just now in another
reply.

When looking at the headers of the different emails, it seems that most of
the problems stem from email clients that don't know how to deal with
several Unicode forms and other common character sets.

Gerhard

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