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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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9th Jul 2019, 9:37 pm | #1 |
Pentode
Join Date: Oct 2009
Location: Bergen, North Holland, The Netherlands
Posts: 180
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Curious circular slide rule
Something surprises me.
I just bought this military slide rule for fun. (and it was cheap). The backside gives most popular formulas.In top is the explanation for sin,cos and tn. Instead of giving the right angle in 90 degrees,it says 1600 pro mile or 0/00. What does this mean or is this normal in the military artillery? Jard N. Last edited by neutronic; 9th Jul 2019 at 9:53 pm. |
9th Jul 2019, 11:15 pm | #2 |
Octode
Join Date: Dec 2010
Location: St Ives, Cambridgeshire, UK.
Posts: 1,180
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Re: Curious circular slide rule
Nice rule, made by ALRO in Holland. The 'pro mile' bit is the same thing as something you may have heard called 'mils'. 1600 mils is 90°, 6400 mils to a NATO circle.
Andrew
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10th Jul 2019, 10:20 am | #3 |
Pentode
Join Date: Oct 2009
Location: Bergen, North Holland, The Netherlands
Posts: 180
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Re: Curious circular slide rule
Thanks Andrew.
I did not know that,I have no military background. In fact,I found this slide rule while looking for one special model I knew from the past. A pocket model made to the specifications by the firm I used to work for. At one side the relation between L, C and frequency. And at the other side a voltage across a resister giving a certain dB value. Even today very useful But this model is rather scarce. Jard N. Pictures:Alro 746 circular slide rule 6cm diameter |