🚀 go-pugleaf

jronnau@kuhub.cc.ukans.edu writes:

>dBuV is a logarithmic-relative measure defined as follows:

>     dBuV = 10*log10( x uV / 1 uV)
>          where x is the voltage in microvolts.

>This relationship yields:
>     1 uV => 0 dBuV
>     2 uV => 3 dBuV
>    10 uV => 10 dBuV
>   100 uV => 20 dBuV

>dBuV is a nice shorthand way of describing wide dynamic range measurments.

>Jim Ronnau
>JRONNAU@KUHUB.CC.UKANS.EDU

This is not  actually correct the factor of 2 is missing.  The correct
story is as doherty@melpar (Kevin Doherty)  writes:

> dbuV = decibels referred to one microvolt; ie, 0 dbuV = 1 uv; 20 dbuV is
>10 uV; 40 dbuV = 100 uv; 60 dbuV = 1 mV; etc.  dbuV = 20 log (volts)
>


  Bels are the log of a power ratio and decibels are 10ths of a bel.

i.e.	value in decibels is 10 * log(p1/p2)

	p2 is your reference power.  There are various standards used depending
on what you are measuring (e.g. threshold of hearing for sound levels).

   As we all should know power is proportional to voltage squared so
the ratio is then (v1/v2) squared  This is the same as multiplying the log by 2
so the formula becomes:

	value in decibels is  20 * log(v1/v2)

   The actual value depends not only v1 but v2 if we choose v2 as 1 uV then we
have:

	value in decibels reference 1 uV (dbuV) is 20 * log(v1/1uV)
or
	value in decibels reference 1 uV (dbuV) is 20 * log(v1 uV)



  Hope this clears up any confusion over the slightly differing explanations
given previously.


		Garry
-- 
Mail:	Garry Wardrope, Computing Science Dept.,  Tel: (041) 339 8855 x5322
	Glasgow Univ., 17 Lilybank Gardens, Glasgow G12 8QQ, UK. 
email:	gjw@dcs.glasgow.ac.uk
".. and even if I came in sight of paradise what price its moon without Marsco"