diy thermometer sensitivity

Why not just right-shift by 7?

-3/4 = -0.75, which you can't express in 4 bits.

He needs more bits. If the ADC is 12 bits, load its data into the upper 12 bits of a 16 bit word. Then you can signed-right-shift 4 and not lose any bits.

Or load it into the ms 12 bits of a 32-bit word, and you can shift/divide more.

I do some controllers in S32.32 math, signed 64 bits with the decimal point in the middle. It's as good as floats for most any physical reality, and much faster if you don't have hardware fp.

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.

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,

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.

yeah,

degree

ethanol)

zeotrope at around 78 degrees (seems like the exact number depends on which source you read 78.2? 78.3? 78.5? I give up)

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 ethanol)

azeotrope at around 78 degrees (seems like the exact number depends on whi ch source you read 78.2? 78.3? 78.5? I give up)

Yup. It then becomes a diffusion problem (super slow compared to boiling).

Now that I remember back from Organic Chem class, there is vacuum distillat ion. Less heat required for boiling, but now it's a trade-off because you have to power the vacuum pump.

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

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

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

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

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

As far as I know condensation of any liquid is illegal in the united states - let alone distillation. Fermentation doesn't seem to be a problem so long as the local bomb sqaud doesn't confiscate all your worldly posessions.

If they find out that you are actually trying to condense water they become very aggregated and start to insist that your are hinding something. Maybe it's in the ``ether''? still dunno.

The use of teflon is not legal. It contains floride wich is a non-potable metal contaminate (i.e., water that contains floride from unnatural sources is considered "unsafe to drink".). I am unable to find an MSDS on PTFE T-27730A on the google.

what is food grade steel? just curious.

I believe the big issue is "the transport of distilled spirits". It is not legal to transport distilled spirits - even as evidence (this may vary accorrding to which state the "transportation occured" in.). One raises the question - what is in the bottle, no?

Me either.

They probably want to know what strain of yeat(s) you are using. If I remember correctly some yeast will "die off" at 14% alcohol. You might need to count your grains of corn and grains of sugar.

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 when I ordered them. I had done a little reading before, 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 depends upon the use and the construction. I've read about 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

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.

Michael