MEW 269 Temperature controller

Duncan- it's 10 squared divided by 5. Equals 20.

10²/5 = 20

10^2/5=2.5118864

I've got a book that raises to the power 1/2 in formula rather than use square root signs, as in 16^1/2=4

I guess it was done that way to avoid using a special maths font. Can anyone think of a mathematical reason for that fractional notation?

Dave

Edited By SillyOldDuffer on 16/06/2018 17:58:53

Ok then how about

(10^2.5 + 12⁴)/5³

you'd have to write 10 raised to the power of 2.5 plus 5 raised to the power of 4 all divided by 5 raised to the power of 3, and it is still ambiguous, what is being raised to the power 3?. As I said, proper notation was invented for a reason, if only to save ink.

BODMAS (or BIDMAS) is the mathematicians rule.

Grizzly, Alt + 0216 is useful as well for the diameter symbol. I can't do the diameter symbol with my pad's keyboard but it does have a degree symbol.

Martin C

The man's correct, but I'm not giving up on proper notation, Neil will just have to live with it!

A new level of pedantry coming next, shock horror!

0216 isn't the diameter symbol, it's a Latin O with stroke - Ø

2205 is the real McCoy - ∅

See the difference ∅Ø∅Ø∅Ø! That nasty embellished Ø would never appear on a proper technical drawing. In future marks will be deducted for getting this wrong...

Edited By SillyOldDuffer on 16/06/2018 22:20:07

Nowadays it would be more sensible to use SQRT(.... and similar.

.

Interesting, Dave ...

I checked your big 'Unicode Table'

Searching for 'Diameter Sign' returns U+2300 not U+2205

U+2205 is identified as the 'Related character' for an Empty Set

MichaelG.

.

P.S. neither of them seems to be available in some popular fonts.

Temperature should present no problem - just use the Kelvin scale and all these superscripts are unnecessary.

Trouble with this thread is that the writer is likely a hobbyist, not a specialist in the field. Practical, not so theoretical, so if it worked it was near enough for most. Probably sufficiently precise as well - even if not absolutely accurate.

If I recall correctly ALT plus a decimal code on the numeric keypad used to work on this forum. Now it takes me to my browser home page. WTF? I'd argue that an inserted symbol is not formatting and therefore the publishing software should not remove it. Of course the best way to reduce errors is for the author to approve a proof prior to publication. That is standard for professional technical journals, but not really practical for ME or MEW. Although I have done it once for ME, with an article that contained some involved equations. To avoid hiccups Diane sent me a proof to check before printing.

To get back to the original thread topic I've now had a quick read through the article. It may well be true that a given set up is good enough, and only the user can determine that. But no mention of using independent temperature measurement is made, so presumably we have no idea how far out the control may be. Sadly it is also clear that the author doesn't understand PID controllers. The initial graphs showing underdamped, critical and underdamped responses are mislabelled, and in the case of underdamped wrong. Unfortunately the text description is also incorrect. While I wouldn't expect MEW to be overly theoretical it ought to at least be technically correct.

Andrew

Would it not be easier and quicker to just write "deg. cent." or "dia." than go thru' all those codes ?

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Yes of course it would, Gordon ... but Dave introduced a magnificent pedantry, which I felt obliged to follow-up.

MichaelG.

Bother, the diameter symbol in my CAD package is definitely a circle with a diagonal, but it certainly isn't lower case.

The whole point of using symbols is that it is easier, and less prone to misinterpretation, than words. It'd be a right royal PITA if one had to write out in full the kilograms, metres and seconds and so on every time you used an SI unit, rather than just using the agreed abbreviation.

Andrew

Ø

Looks like a browser issue, not one with the website...

I also try and strip out things like that which affect the readability of text, as well as abbreviations like 'BMS'* (if used a lot I will add expand the abbreviation once for the sake of beginners. I am not perfect and sometimes miss examples.

Neil

*BMS is particularly ambiguous as some people use it for 'bright mild steel' and others for 'black mild steel'.

Good spot! The plot thickens:

U+2300 = ⌀

U+2205 = ∅

Unicode is a sort of unifying super-font. Older fonts were limited by technology to 8-bit characters (max 256). Unicode is extensible and able to use 8, 16 or 32 bit numbers to represent gigantic numbers of different symbols. The latest version defines about 150,000 symbols.

Older software and printing technologies are stuck with less flexible font systems; to get more characters you have to load another font. Having to manage multiple fonts is limiting and causes serious incompatibility problems. One reason Word documents are so big is they often include a copy of the fonts used as well as what was typed. 

Unicode isn't perfect, but it does much to reduce the problem. Being universal, it's a feature of systems rather than individual documents, and it doesn't have to be copied about. Unfortunately, rather a lot of software has yet to catch up with Unicode, and - even when it does - we're probably stuck with the older font systems for ever. The number of legacy documents produced with ancient versions of MSWord must be enormous.

Dave

Edited By SillyOldDuffer on 17/06/2018 19:58:32

Don't tell me, I need to get a life, but this unicode thing got me interested. I use Libre Office running under Windows 7. The U+ doesn't work, but if you type 2300 then hold down the alt key and type x, release both and wait for a split second it converts the 2300 to a diameter sign. How neat is that. It seems to work with the other unicodes, but obviously I've not tried them all. Could someone who runs Word under Windows try this out and see if it works?

Duncan, yes that seems to work in Word.

Duncan:-
'wasn't aware of your 'trick' ~ good one !. That below is a cut'n'paste from Word 2007 apart from the italic text.

Using Windows 10 with Calibri (Body) type face:-

(Alt+2300), release Alt = strange character like O with umlaut

“if you type 2300 then hold down the alt key and type x, release both and wait for a split second
it converts the 2300 to a diameter sign.” = ⌀