What is the relationship between output voltage(PktoPk)+dB?

[strangeandbouncy]

Wonder if anyone can help me . . . i am sure that there must be a simple formula . . . .


Duh . . ..

strangeandbouncyTigger . . . [/i]

 

[[silent:arts]]

http://www.sowter.co.uk/decibels.htm (voltage is rms)

this will help

 

[clintrubber]

You want to convert a peak to peak sine level to an RMS-figure expressed in dBu ?

First divide 'peak-to-peak' by two to get 'peak', then divide by sqrt(2) to get the RMS value, then divide by 0.775 to reference to dBu and then do a log and finally multiply by 20.

So a 20Vpp level equals +19.2 dBu if I did my button-pressing correctly.

Bye,

Peter


PS

Wouldn't it be an idea to start using Bells i.s.o. dB's ? That 10-scaling will be historical I guess, so hard to change. But what use it has... ?

Could also be fun as some kind of secret code for Lab-people, so that we can recognize each other outside this place. :wink:
So 20Vpp becomes 1.92 B(ell).

 

[strangeandbouncy]

Wow!

thank you guys!

what can i say? so quick!

gratitude,


AndyP

 

[NewYorkDave]

Or, if you wanted to express it in a more compact form:

dBU = 20 * log (Vpk/1.095)

Where Vpk is the peak value (simply half of the pk-pk value) and 1.095 is the peak value of 0dBU. (0.775 * √2).

And if you're working with an RMS value (which is what an AC voltmeter usually displays) and want to convert to dBU:

dBU = 20 * log (Vrms/0.775)

 

[peterc]

Practically, when I set up the +20dB peak light on the Green meter, I set the gain to give me about 22v pk-pk, then trim in the meter amp to just light the red LED.

However, it's not easy to see 22v pk-pk exactly on a scope, so I measure the output using an AC voltmeter & set the gain for 7.75v (+20db). Before trying this, check your voltmeter as some dont like higher frequencies, & will give bad readings above 500Hz in my experience.

Still, its ok to use a 100Hz signal, if it's a flat circuit.

Peter