Maths Help - LOG &a...
 

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Maths Help - LOG & LN

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 moff
Posts: 177
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Topic starter
 

We have a calculation supplied by a client this uses LOG and is required in our logic control, but the PLC can only use Natural Logs - LN.

Is there a method or calculation to convert? Can it even be converted?


 
Posted : 09/11/2022 4:07 pm
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ln(x) = 2.303 * log(x)

Approximately


 
Posted : 09/11/2022 4:14 pm
Posts: 403
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Google (well neeva in this case) says yes.

https://faculty.washington.edu/djaffe/natlogs.html


 
Posted : 09/11/2022 4:24 pm
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Care needed. XL uses LN for natural logs, other softwares might use LOG.

To convert between logs; Log10(x) = logn(x)/logn(10) where logn is natural log which XL writes as LN(). logn(10) = LN(10) = 2.3025851 which is the conversion factor above.

I much prefer log10 and log as notations to avoid confusion and try and avoid XL where possible. It's an easy source of error.


 
Posted : 09/11/2022 4:58 pm
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As above becareful that it is actually log base 10 as some software uses log to mean ln for some reason


 
Posted : 09/11/2022 7:52 pm
Posts: 13594
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Very easy to convert logarithms between any bases by just dividing by log of the base.

NB Worth checking that their original calcs do use LOG and not LN etc as many people confuse the two...


 
Posted : 09/11/2022 8:33 pm

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