reading an oscilloscope

hi all

just a quick question. i have built a circuit
in NI software. and there are various virtual
bench tools. one of which is an oscilloscope.
i have used it to measure the output of an
LM358 which amplifies the input of an electret
mic. initially i thought i was only getting a reading
of about 50 odd mV, however i now think i should
have taken the measurement above and below the
zero line. i believe this is called peak to peak?
reading Pk-Pk gave me a total of 125mV. so is
the Pk-Pk the correct reading or is it only whats
above the zero line thats inportant. i also set the
osci' to AC rather than DC for the reading.

Regards

Fenris

Your circuit plays the audio through a speaker. The audio is not rectified to turn on an LED.
The speaker must move back and forth when the audio voltage swings positive and negative. The sound would be extremely distorted if only the positive part of the signal is passed and the negative part is missing.

if you want to know the gain then peak to peak is important, also if you are dealing with a sine wave that swings pos to neg then ac is the appropriat setting. you should take sometime to get to know how to use an oscope it would help alot.

thanks guys
i am in the middle of reading about the
use of oscilloscopes as it would,you'll
agree, be better if i understood rather
than just had an impression of how you
use them.

Regards

Fenris

Don't use the LM358 as a microphone aplifier, use the TL072.