Author Topic: Oscilloscope reference lead earth issue in audio circuits  (Read 1716 times)

0 Members and 1 Guest are viewing this topic.

Offline ÖttiTopic starter

  • Newbie
  • Posts: 4
Oscilloscope reference lead earth issue in audio circuits
« on: January 30, 2017, 02:33:47 pm »
Hi folks!

Do u know Dave's blog #279? Please take a look at minute 6:35 (https://youtu.be/xaELqAo4kkQ). He sais that doing measurements on a floating audio circuit could cause problems when connecting the scopes reference lead to a particular point in the circuit.

Can someone please explain me why. I have no idea. And I dont really unterstand the last word he sais at the end of the sentence at 6:35. What can happen worst case?


Thanks a lot!
 

Offline Andy Watson

  • Super Contributor
  • ***
  • Posts: 2142
Re: Oscilloscope reference lead earth issue in audio circuits
« Reply #1 on: January 30, 2017, 04:40:38 pm »
6:28
" It may not do anything, in most cases it is not going to cause a problem at all. Unless there is some, you know, your working at audio circuits and there is hum and all sorts of things ...".

What he is saying is that if you connect the scope earth to a sensitive, high impedance part of the circuit under test it will behave like an antennae and inject some signal - probably main's hum - into your circuit. (It is actually your floating circuit that is the antennae, but the effect is that same.)
 
The following users thanked this post: Ötti

Offline ÖttiTopic starter

  • Newbie
  • Posts: 4
Re: Oscilloscope reference lead earth issue in audio circuits
« Reply #2 on: January 31, 2017, 08:12:30 am »
Thanks a lot Andy!

Greetings from overseas   :-+
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf