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Old 30th Jul 2019, 7:17 pm   #1
mole42uk
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Default Drawing circular log scales?

I need to make a circular log scale to replace the missing one on a signal generator but I canít find any way of generating a software based version.

Is there something Iíve missed? Can anyone help?
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Old 30th Jul 2019, 10:56 pm   #2
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Default Re: Drawing circular log scales?

I am not aware of software, but have not needed or looked. It is something which may be not too difficult to do by hand. You only really need the length of circle perimeter (or length of the scale if not full circle) then calculate a normal straight log scale to fit that length. Then transfer over. I can see it would be tedious but with the right tools, practical.

Hopefully someone will have done this and know the tricks (or better still - software).

One other option would be if someone were able to take an accurate photograph of such a scale from identical model.
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Old 31st Jul 2019, 5:09 am   #3
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Default Re: Drawing circular log scales?

Something like this?

Done with Abacom's Front Designer, all customisable.

Change text, rotation, line lengths etc within the program.
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Old 31st Jul 2019, 8:19 am   #4
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Default Re: Drawing circular log scales?

Hmmm... Can't have '0' on a log scale!
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Old 31st Jul 2019, 9:48 am   #5
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Default Re: Drawing circular log scales?

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Originally Posted by kalee20 View Post
Hmmm... Can't have '0' on a log scale!
That's right. The one I have is a photocopy of an original, it reads from 10 to 100 over an arc of 290į on a diameter of 4.25" (108mm).

I want to produce a drawing so that I can send it off to have one made in etched aluminium.
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Old 31st Jul 2019, 11:44 am   #6
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Default Re: Drawing circular log scales?

Removed the 0 and changed it to 290deg scale.
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Old 31st Jul 2019, 12:02 pm   #7
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Default Re: Drawing circular log scales?

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Originally Posted by Terry_VK5TM View Post
Removed the 0 and changed it to 290deg scale.
Thank you! Please could you change it so the marks are on the inside of the arc and reverse it so that 10 is where 100 is? That would be an excellent solution!!
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Old 31st Jul 2019, 12:12 pm   #8
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Default Re: Drawing circular log scales?

Quote:
Originally Posted by Terry_VK5TM View Post
Removed the 0 and changed it to 290deg scale.
I've just crudely put a ruler on my monitor face and measure chord lengths: 10-20; 12-24; 20-40; 30-60; 40-80; 50-100 all measure 72mm. so the angles are the same, exactly what would be the case for a log scale!

I like it
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Old 31st Jul 2019, 1:20 pm   #9
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Default Re: Drawing circular log scales?

Quote:
Originally Posted by kalee20 View Post
Hmmm... Can't have '0' on a log scale!

In principle, that's correct. A real life pot will jump to zero at the end of the track, though.....
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Old 1st Aug 2019, 4:17 am   #10
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Default Re: Drawing circular log scales?

Quote:
Originally Posted by mole42uk View Post
Thank you! Please could you change it so the marks are on the inside of the arc and reverse it so that 10 is where 100 is? That would be an excellent solution!!
Household chores to finish today so I'll change it around tomorrow for you.

Do you want the arc to remain where it is and the division marks come in from there

Or

Move the arc to the outside of the division marks as they currently are?

And do you want the lines slightly thicker?
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Old 1st Aug 2019, 6:02 am   #11
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Default Re: Drawing circular log scales?

So much for the household chores, started raining and of course it was outside chores.

Attached as first pass depending on which way round you want the changes.

Also attached as a pdf as that is nicer than the jpg's.
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Name:	Log Scale 2a.jpg
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File Type: pdf Log Scale.pdf (58.2 KB, 18 views)
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Old 1st Aug 2019, 3:01 pm   #12
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Default Re: Drawing circular log scales?

Hi Terry, thank you, it's looking almost right!
I attach a photo of the dial I'm trying to duplicate, I don't know why I didn't do this before....
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Old 1st Aug 2019, 3:44 pm   #13
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Default Re: Drawing circular log scales?

You might want to have a play with meterscales, I can't offer any help with the program.
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Old 1st Aug 2019, 5:46 pm   #14
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Default Re: Drawing circular log scales?

Quote:
Originally Posted by Alf View Post
You might want to have a play with meterscales, I can't offer any help with the program.
Thank you, unfortunately I don't have a Windows computer....
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Old 2nd Aug 2019, 1:41 am   #15
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Default Re: Drawing circular log scales?

Picture was a good idea.

I'll have a play a little later and see how close I can get it.

Are you able to measure the distance between the end of the division mark and the number and the lengths of the marks?
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Old 2nd Aug 2019, 3:00 am   #16
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Default Re: Drawing circular log scales?

There are ways round operating system issues.

This Mac has Oracle Virtual Box installed. This creates a number of virtual machines and I can load any operating system I want on each machine. so I got a legit copy of XP. I can open a window on the Mac OSX screen with XP running in that window, and run windows software on it.

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Old 2nd Aug 2019, 11:13 am   #17
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Default Re: Drawing circular log scales?

This is about as close as i can get it from the picture.

Let me know if it needs any tweaks.
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Old 2nd Aug 2019, 11:37 am   #18
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Default Re: Drawing circular log scales?

Hi Terry, that is fabulous! Thank you, I'll be able to finish rebuilding the signal generator...
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Old 2nd Aug 2019, 11:39 am   #19
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Default Re: Drawing circular log scales?

Quote:
Originally Posted by Radio Wrangler View Post
There are ways round operating system issues.

This Mac has Oracle Virtual Box installed. This creates a number of virtual machines and I can load any operating system I want on each machine. so I got a legit copy of XP. I can open a window on the Mac OSX screen with XP running in that window, and run windows software on it.

David
Hi David,
I have run Virtual Box on the Mac but I don't have a currently licensed version of any Windows system.
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Old 2nd Aug 2019, 3:02 pm   #20
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Default Re: Drawing circular log scales?

If you know how to write PostScript, it would take about a screenful of code to produce a scale like that!

If you are running any Unix-like system (i.e., Mac or Linux) then you probably already have GhostScript installed, which is a suite of programs for working with PostScript files including displaying them and converting them to other formats.
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