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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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22nd Sep 2018, 1:59 pm | #21 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,874
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Hi!
I can confirm this was very common practice in the 1920s and 1930s - if you look in Practical Wireless, Ameteur Wireless and early editions of the "Wireless Encyclopaedia" you'll find this notation frequently cropping up, so yes, 50,000ω is 50kohm and 2Ω is 2megohm! By the time "preferred values" were introduced this notation had become totally obsolete! Subsequently it became more common to write the unit in capital letters, e.g., "50,000 OHMS", particularly in the mid to late 1930s, then the transition-point to today's shorter methods of writing component-values, was in my opinion, about 1940-1943 - the exact date did tend to vary between the various magazine publishers and set-makers! Chris Williams
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22nd Sep 2018, 2:26 pm | #22 | |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Quote:
Never mind- engineers and schoolboy humour are common bedfellows! Scatological terms for mnemonics, tools and test equipment are easier to remember than clean ones, too. ES light bulb with side handles sketch ring any bells?
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....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
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22nd Sep 2018, 3:18 pm | #23 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Thanks Terry, but I use an iPad, and I don’t seem to be able to add any other mathematical symbols etc.
Cheers John |
22nd Sep 2018, 3:18 pm | #24 |
Heptode
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 539
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
The use of Ω to represent Megohm was certainly common in the 1920's, attached is a typical circuit from Harmsworth's Encyclopedia showing a 2 Meg grid leak resistor.
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22nd Sep 2018, 3:22 pm | #25 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Just wondered how would they represent 2ohms?
Cheers John |
22nd Sep 2018, 4:23 pm | #26 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
2ω.
If they've already been used in a thread, the easiest way is cut and paste - which I used above rather than opening up Character Map..
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22nd Sep 2018, 4:47 pm | #27 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
You can add a Greek keyboard from the setting menu on the iPad, I have just added one.
Π ω Ω β etc You can also install mathematical keyboards from the store.
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Frank |
22nd Sep 2018, 5:25 pm | #28 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Thank you Frank I didn’t know that.
Cheers John |
22nd Sep 2018, 5:26 pm | #29 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,887
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Thank you also Dave.
Cheers John |
22nd Sep 2018, 6:12 pm | #30 |
Pentode
Join Date: Oct 2016
Location: Maldon, Essex, UK.
Posts: 184
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
On, April 15, 1867 W. H. Preece from the Electric and International Telegraph Company, Southampton Station, suggested use of the letter Omega from the Greek alphabet as a symbol for resistance because of its similarity in name with the British Association (B.A.) unit “Ohm”, using the small letter (ω) for B.A. units and the capital (Ω) for B.A. units x 1,000,000. He suggested that the symbols would be superscript and read “Ohm and Megohm”.
Now SI requires that unit names, such as “ohm”, are not normally capitalized and unit symbols, such as “Ω”, are capitalized when derived from the name of a person, in this case German physicist Georg Simon Ohm. The letter written by W. H. Preece can be found here in reference 15: https://en.wikipedia.org/wiki/Ohm David Last edited by Neutrino; 22nd Sep 2018 at 6:16 pm. Reason: Added commas |
23rd Sep 2018, 7:55 am | #31 |
Rest in Peace
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
I have see "ω" marked on headphones, so wondered if it referred to impedance, as in 2000ω.
Mike |
23rd Sep 2018, 1:14 pm | #32 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Well it does, in a way, but nothing to do with its radians/sec usage.
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....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
25th Sep 2018, 8:35 pm | #33 |
Heptode
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 539
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
I've attached a Windows text file which contains a range of characters that I find useful in radio, electronics and maths.
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25th Sep 2018, 11:43 pm | #34 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
Very handy, that. I couldn't find the Ʊ symbol for Mho in the Libre Office WP.
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....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
26th Sep 2018, 12:07 am | #35 |
Dekatron
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Location: Bewdley, Worcestershire, UK.
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
I remember at school an elderly physics teacher insisted on using "ω" for ohms and "Ω" for Megohms.
I think I have also seen old Murphy (?) service sheets where the capital letter "O" has been used to indicate Megohms.
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26th Sep 2018, 8:28 am | #36 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
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Re: 'ω' and 'Ω' versus 'Ω' and 'MΩ'
That’s right Julie , that’s where I regularly see this specialist character, to represent radians ... (can’t reproduce on an iPhone keypad!)
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Al |