How many amps Can I pull safely???

[ban-all-sheds]

Back in the day when (some) laser printers had plug-in font cartridges, some enterprising person produced one containing a 2-point font so that people could print large spreadsheets.

 

[JohnW2]

Back in the day when (some) laser printers had plug-in font cartridges, some enterprising person produced one containing a 2-point font so that people could print large spreadsheets.

Untitled

• JohnW2
• 19 Jun 2013
• 1

Kind Regards, John

 

[ban-all-sheds]

A3 says it all.

 

[JohnW2]

A3 says it all.

It does indeed. For a project I was involved with fairly recently, in order to be able to see an 'overview' of the data, we had spreadsheets printed out on A1 paper, using as small a font as we dared (IIRC 5pt or 6pt).

Kind Regards, John

 

[ericmark]

Think I still have a slide rule some where with a log log scale. Or may be J is imaging it?

 

[JohnW2]

Think I still have a slide rule some where with a log log scale. Or may be J is imaging it?

All decent slide rules had log log scales (usually in the middle of the sliding bit, IIRC) - one needed them for calculating 'powers'.

Kind Regards, John.

 

[ericmark]

I had to learn how to use one in college but by that time I was very quick using log tables so only used it to pass test never really used it to work out sums. For one thing I kept getting decimal point in the wrong place. If I knew approx what the answer was OK.

Clearly later used calculus where we found log of log but not with slide rule. Still have slide rule and for simple calculations like watts into amps very handy but as soon as it starts to get complex then it's the electronic calculator or excel.

As for imaginary numbers calculator is used. Sure you can use Excel but never tried.

 

[JohnW2]

I had to learn how to use one in college but by that time I was very quick using log tables so only used it to pass test never really used it to work out sums.

My A-Level and undergraduate days pre-dated electronic calculators (we had some use of 'mechanical' calculating machines at uni) - so we were totally dependent upon slide rules and log tables. Exam questions usually indicated when (not very often) 'answers to 4 significant figures' were required, in which case one used tables - otherwise everything was done with slide rules.

For one thing I kept getting decimal point in the wrong place. If I knew approx what the answer was OK.

The ability to rapidly estimate the approximate answer (by mental arithmetic and/or scribbles on paper) is as important today (because it's so easy to mis-key into a calculator) as it was back then (because of the decimal point issue with slide rules). I found it reassuring to see that such 'approximate estimation' was part of the GCSE maths syllabus when my daughters were doing them (in the mid-late 90s).

Clearly later used calculus where we found log of log but not with slide rule.

As I said before, the main purpose of a log log scale on a slide rule is to calculate powers (e.g. 23 to the power 3.7), not to determine 'log log' values.

Kind Regards, John

 

[SimonH2]

Think I still have a slide rule some where with a log log scale.

Slide rules generally work by having log scales. Example : Multiply A * B.
The answer can be done by additional as Alog (log A + log B). So starting from 0 on the fixed scale, move along by a distance of A on the scale. Align the zero mark of the moving section to here. Now move along to value B on the moving section - and read across back to the fixed section. You've added log B to log A, and because the scales are log anyway, you've done the anti-log just by reading the scale.

For even more fun, try a "whizz wheel" as used in aviation - or at least, used only until you've proved you can use one and then you never touch it again !
Actually they are quite useful - unless you have an electronic calculator handy which is a lot quicker and easier.

 

[JohnW2]

...Example : Multiply A * B.
The answer can be done by additional as Alog (log A + log B). So starting from 0 on the fixed scale, move along by a distance of A on the scale. Align the zero mark of the moving section to here. Now move along to value B on the moving section - and read across back to the fixed section.

Roughly right - except for 0/zero, read '1' (you don't get a zero on a log scale).

If you want a very long scale, hence high precision, in a slide rule, albeit only for simple multiplying and dividing, I still have this cylindrical job in my drawer:

Untitled

• JohnW2
• 18 May 2011
• 2

Kind Regards, John

 

[SimonH2]

Roughly right - except for 0/zero, read '1' (you don't get a zero on a log scale).

Doh, you can tell it's a long time since I've used one can't you Must try one out on the youngsters at work one day

 

[ban-all-sheds]

For even more fun, try a "whizz wheel" as used in aviation - or at least, used only until you've proved you can use one and then you never touch it again !

I've got one of those - if you think about it it's a slide rule for vectors.

Actually they are quite useful - unless you have an electronic calculator handy which is a lot quicker and easier.

Useful to have and know how to use one if for any reason all your electronic aids stop working.

 

[JohnW2]

Useful to have and know how to use one if for any reason all your electronic aids stop working.

Indeed - along with a sextant!

Kind Regards, John

 

[Porque223]

For me, I expand the trip curve image on my screen, measure it with a ruler and then convert back & forth to find the trip time interval.
There's very little of the trip curve that follows I-squared-T.

You guys seem more knowledgeable than US electricians.

 

[bernardgreen]

You guys seem more knowledgeable than US electricians.

Maybe you are mixing with the wrong "electricians"

Putting the word in quotes implies a suggestion the word may not be an accurate description of the item it refers to.