# diy thermometer sensitivity

D

#### Daniel Pitts

Jan 1, 1970
0
Why not just right-shift by 7?

-3/4 = -0.75, which you can't express in 4 bits.
My example was meant to find the whole number result, truncating the
fractional part. This seems likely the use-case that the OP was
concerned with as well.

Actually, my point was (and I was too sleepy to think of it when I wrote
that), is that shift-right (if using a signed shift), will always
"floor" the result. Many people expect it to round toward zero, since
indeed that is what it does for positive integers.

J

#### Jasen Betts

Jan 1, 1970
0
I'm an 80x86 guy (and not the OP), but I'm curious about what you're
I would either need a real "divide" instruction, or I would need to
check the sign, and then if < 0, I would negate and shift and negate
back. Unless there is some other nifty trick I'm missing. I'd love to
see it.
Either way, if the OP wants to use (x >> 7) in C, they will find
negative values of x don't result in the desired value of x/128;

IIRC this was for signal processing and rounding towards 0 will
introduce crossover distortion so the rounding down that you get from
a bit shift is may be more useful,

J

#### Jasen Betts

Jan 1, 1970
0
On Sat, 15 Jun 2013 22:46:18 -0700, Daniel Pitts

Why not just right-shift by 7?

the only way to do that on the AVR is to shift right by 1 and repeat
that 7 times.

Overshoot then reverse by 1 is going to be atleast 4 times faster.

G

#### George Herold

Jan 1, 1970
0
First time I did mashed potatoes up here in Truckee, they came out
raw. It takes a full hour. At higher altitudes, it might not be
possible without a pressure cooker.

Just speculating, but if you just slowly add heat to a water-alcohol
mix, won't the alcohol boil off first? It's sort of self-regulating. I
don't know how pure the distillate would be.- Hide quoted text -

- Show quoted text -

I'm guessing that unless it starts to boil, you just don't get much
vapor.
(I was going to suggest sci.chem... but that looks to be full of many
of the same 'characters' as are on sci.physics.)
(maybe we could ask Bill Sloman on SED?)

You'll get some partial pressure of each gas in the vapor.
I should dig up my general chem. book. I don't recall any sort of
practial discussion of distillation... maybe that's only covered in
chem. eng.

George H.

M

#### [email protected]

Jan 1, 1970
0
I'm guessing that unless it starts to boil, you just don't get much

vapor.

Yup. It then becomes a diffusion problem (super slow compared to boiling).http://en.wikipedia.org/wiki/Fick's_law

Now that I remember back from Organic Chem class, there is vacuum distillation. Less heat required for boiling, but now it's a trade-off because you have to power the vacuum pump.
https://en.wikipedia.org/wiki/Vacuum_distillation

I remember using vacuum distillation to make DEET in Organic Chem class, I think it was because the DEET would decompose at atmospheric boiling temperatures.

(I was going to suggest sci.chem... but that looks to be full of many

of the same 'characters' as are on sci.physics.)

(maybe we could ask Bill Sloman on SED?)

You'll get some partial pressure of each gas in the vapor.

Yup, Henry's Law and Raoult's Law. Ethanol-Water mixtures are non-ideal solutions though (the ethanol and water molecules like each other too much)

https://en.wikipedia.org/wiki/Henry's_law
http://en.wikipedia.org/wiki/Raoult's_law

Oh yeah, fugacity coefficients. These guys explain it much better than my Thermo text ever did...

http://en.wikipedia.org/wiki/Fugacity_coefficient

I should dig up my general chem. book. I don't recall any sort of

practial discussion of distillation... maybe that's only covered in

chem. eng.

George H.

I'm a refugee from sci.engr.chem personally =)

It's discussed a little bit in Organic Chemistry (chemistry for second-yearBiology and Chemistry majors.)

J

#### Jon Kirwan

Jan 1, 1970
0
<snip>

< food grade stainless) allowed legislators to justify keeping
< a strong hold on the tax revenues for hard liquors.

what is food grade steel? just curious.
<snip>

I'm no expert. I was simply cautioned to specify food grade
stainless and contruction methods when buying some long term
storage containers, so I did and wasn't questioned about it
though, and the following summarizes what I'd gathered up.

There are certain types of stainless alloys and annealing
used for food handling and containers. I gather what is used
types 302, 303, 304, 316, 420, and 430. (303 doesn't weld
well, but machines okay, for example. So an application which
requires welding wouldn't use it.) I think there is more than
just "type" involved. For example, there are 304L and 316L
types used for food. You may also have to watch out for
additives, like sulfur, used to improve machining. Type
number alone may not tell you all you need to know.

From "The Making and Shaping of Steel" from United States
Sttel: Type 302, austenitic 18-8 with 0.15% max carbon, 8% to
10% nickel, and 17% to 19% chromium is corrosion resistant
and has good ductility and may be deep drawn and formed. It
may also be welded if the heat zones are cooled rapidly.
(Otherwise intergrannular corrosion may happen in the welds.
But that can be corrected by annealing above 1900F, followed
by rapid cooling to trap the carbides in situ.)

It's also not only a type of steel but also how you handle
the design and finishing methods to sufficiently reduce pits
or anything else that may promote bacterial growth and also
to provide surfaces that can be reliably (repeatably) cleaned
and sanitized. You know, the welds need to be smooth for
example and not deeply pitted, for example.

But you can't ignore the type of steel. The selection is
limited by the food it will contain, duration, environment,
and the methods of cleaning and reuse.

I wish I knew more about the subject, but I'm a consumer not
a designer of these products.

Jon

M

#### [email protected]

Jan 1, 1970
0
I'm no expert. I was simply cautioned to specify food grade

stainless and contruction methods when buying some long term

storage containers, so I did and wasn't questioned about it

though, and the following summarizes what I'd gathered up.

There are certain types of stainless alloys and annealing

used for food handling and containers. I gather what is used

types 302, 303, 304, 316, 420, and 430. (303 doesn't weld

well, but machines okay, for example. So an application which

requires welding wouldn't use it.) I think there is more than

just "type" involved. For example, there are 304L and 316L

types used for food. You may also have to watch out for

additives, like sulfur, used to improve machining. Type

number alone may not tell you all you need to know.

From "The Making and Shaping of Steel" from United States

Sttel: Type 302, austenitic 18-8 with 0.15% max carbon, 8% to

10% nickel, and 17% to 19% chromium is corrosion resistant

and has good ductility and may be deep drawn and formed. It

may also be welded if the heat zones are cooled rapidly.

(Otherwise intergrannular corrosion may happen in the welds.

But that can be corrected by annealing above 1900F, followed

by rapid cooling to trap the carbides in situ.)

It's also not only a type of steel but also how you handle

the design and finishing methods to sufficiently reduce pits

or anything else that may promote bacterial growth and also

to provide surfaces that can be reliably (repeatably) cleaned

and sanitized. You know, the welds need to be smooth for

example and not deeply pitted, for example.

But you can't ignore the type of steel. The selection is

limited by the food it will contain, duration, environment,

and the methods of cleaning and reuse.

I wish I knew more about the subject, but I'm a consumer not

a designer of these products.

Jon

Food grade... this is not exactly my field either, but you certainly don't want lead in any welds.

18/10 and 18/0 (first number is percent chromium, second # is percent nickel) seem popular in "food grade" stainless steels. Personally I dislike nickel since some have allergies to it. I look for 18/0 in my cookware personally. And besides, iron and chromium are important minerals. Copper too (I think the early Alambic stills were made of copper.) Nickel and lead, not so much.

Michael

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