Is it possible to use a logarythmic scale on a dial / needle? I have a dial where I want the scale 0-20 bigger than the rest of the 20 - 80 scale like I tried to show below

Yes, Iâ€™ve done it on this watch face:

The formula for the dial below for km/h: `(clamp(-180+log10(#WND#*2.57)*130,-180,162))`

Thanks for your quick reply - you just made my day!

You will need a condition when the wind is 0, because log10(0) = infinity.

Without the condition, the hand will just vanish

So add something like: `$#WND#=0?0:myformulahere$

btw. : I made the tickmarks and numbers myself by trying it out. It is pretty difficult to find the logarithmic formula for and existing scaleâ€¦

Yes it is, but the scale on your example only has two linear fields attached at 20, so for the â€śneedleâ€ť you would have to use two formulas switched at that spot like this:

for metric hand `$#WND#<20?#WND#*149/20-149:(clamp(#WND#,0,80)-20)*149/60$`

for MPH hand `$#WND#<44.7388?#WND#*149/44.7388-149:(clamp(#WND#,0,178.9552)-44.7388)*149/134.2164$`

Edit: Check the number of ticks on your scale, there it reads 10 on 11th tick and 20 on 22nd and so on.

I wish I had seen some of this stuff when I was younger . I might have had a Better Paid Career . You guys are great teachers . There must be a way of generating log scales with a macro on a decent graphics Package . Till I got a calculator that was not RPN . I used a Slide Rule at work for Trig and Pi stuff .

Tom Forgive me for not seeing that on you Instrument Face . Thanks for flagging it up again I forgot to put it in my Bits Box Collection .

Tom, to me it seems that the gap between small ticks is constant, just their count between numbers varies. Those small ticks are then actually out of the logarithmic scale?

Yes, I know. Since I used Facer Time Machine to get the approximate values, it is not exact. And so the small ticks have a regular gap. I did not generate them. Something to explore I guessâ€¦

Thereâ€™s no button here to translate from Chinese so I donâ€™t know what you all are talking about lol

Itâ€™s ok you are in good company! Pleased to meet you

If you go to your local Magic shop and ask them for a Good Book on Voodoo I am certain you will find the answer in there .

That was my original idea but the transition at 20 is no good - what I really wanted was two logarithmic scales so to see @tom.vannes answer was ideal. If only I fully understand Tomâ€™s formula - ok hereâ€™s my understanding:

(Clamp(-start + log10(#WND*?)*?,-clamp )between

Iâ€™m guessing that 2.57 is the factor to get the right number of ticks in the range but I have no idea how it is derived - what the *130 is doing I also have no idea!

I have no doubt that with the help of the entire cavalry I might possibly understand - eventually !

I see a some brackets are in the wrong places but I think you can guess what I mean from the text

Ok, sorry, did not explainâ€¦

If you look at the picture, it says km/h, so the #WND#*2.57 converts from m/s to km/h. I did not make logarithmic dial for mphâ€¦

The factor 130 is needed to get the hand around the dial, log10 just gives you small values. I just tried it out to something that works. Only then did I look where the numbers need to be.

Thanks for the info - nice watch faces by the way. I wish I had your drawing skills, or imagination for that matter!

I did not find a way to generate a dial with a logarithmic scale.

What I have done is to take a seconds hand and use the rotations:

`(-180+log10(2)*130)`

`(-180+log10(3)*130)`

â€¦

`(-180+log10(300)*130)`

Used a shape to cover up to get the tickmarks and arc for the rim.

And the main wind hand has the formula: `(-180+log10(#WND#)*130)`

**This draft now supports both m/s and mph.**

Inspection is open:

Pretty tedious, but working good.

I would suggest either to use clamp(#WND#, 2, 500) instead #WND#, or change the formula, because the hand as is points up at 0 and to 0 at 1

I dont know how well would this $#WND#=0?180:(-180+log10((#WND#+1))*130)$ behave between 0 and 1, but it would only need to rename first 4 numbers above 0, adding new 5, new tick for 10 and shifting those from 15 to about 60 accordingly.

Amazing Well Done . Sadly impossible to Sim on Creator. Well for me any way . For us the low speeds are important to judge what sort of day we could have on the beach .