"Phil Allison" wrote in message
...

"Arfa Daily"
"Phil Allison"
"Arfa Daily"


I fired it up again, and put a sine wave in, then hooked up two
channels of my 'scope, one to the "A" output and one to the "B", both
with the same polarity, and was surprised to find that the two signals
were completely anti-phase,


** When servicing audio, knowing the polarity of the test signal and if
there is significant phase shift is important. A scope triggering off
the incoming wave will it not reveal this in single channel mode - so AF
used both channels.

A much better way is to use the External Synch input on your scope and
link it to a fixed output on your bench audio oscillator ( create on if
you have to). This way, you see instantly if the signal's phase has
reversed or has a large phase shift.

Also, triggering will be rock steady with nearly any kind of distorted,
noisy or contaminated signal on the scope screen.

Try it out for a day or two - you will never go back.



Interesting. Are you squaring up the generator's sine output, to give a
good sharp transition for syncing the scope ?

** FFS - that processing is inside any decent scope.

Supply it with 0.5volt rms sine wave and you are away.


I'll have to look at that on my scope, but off the top of my head, I thought
that the trigger point was still adjustable on external and could be set
anywhere on the trigger signal and if so, I'm not sure that I see how it
helps to trigger the scope externally from the same sine wave as it would
use internally on auto trigger. I can see how it would be helpful to have a
fixed trigger point, virtually at the beginning of a cycle, by squaring up
the generator's output, and then feeding that to the external trigger input.

Arfa