PicoScope 7 Software
Available on Windows, Mac and Linux
Proper way to connect a composite video signal?
Proper way to connect a composite video signal?
I'm using a 2206B to record a composite video signal using the SDK and streaming mode from an old Hi8 camcorder.
Its mostly for fun and a way for me (a software guy) to learn about signal processing.
I have decoded a B/W picture and was about to move on to color when I noticed the composite output on the camera all of a sudden looks terrible (verified through a commercial capture card). Large amounts of dot crawl that was not there before. Lots of noise basically.
I'm worried I have damaged the output circuit on the camera by not connecting it properly to the scope.
I've simply used a standard RCA video cable with a RCA->BNC converter attached and then plugged it into channel A.
In passing I've read about terminating a composite signal with a resistor, but I don't know if that applies to my scenario.
Whats the proper way to connect a composite video source to the scope and is it possible I have damaged the camera?
Its mostly for fun and a way for me (a software guy) to learn about signal processing.
I have decoded a B/W picture and was about to move on to color when I noticed the composite output on the camera all of a sudden looks terrible (verified through a commercial capture card). Large amounts of dot crawl that was not there before. Lots of noise basically.
I'm worried I have damaged the output circuit on the camera by not connecting it properly to the scope.
I've simply used a standard RCA video cable with a RCA->BNC converter attached and then plugged it into channel A.
In passing I've read about terminating a composite signal with a resistor, but I don't know if that applies to my scenario.
Whats the proper way to connect a composite video source to the scope and is it possible I have damaged the camera?
Re: Proper way to connect a composite video signal?
I found the solution to this and thought I'd post it here in case someone else ran into the same question.
The right way is to terminate the signal with something like a TV or a 75 ohm terminal plug. You want the scope to tap into the signal on its way to its normal destination.
If you just send the composite signal straight to the scope you will suffer from high amounts of noise caused by the signal reflecting against the scopes 1 M ohm wall of resistance. The reflection is visualized well in this video (https://www.youtube.com/watch?v=AjzBGC4tGTo). The waves bouncing back becomes noise.
If you properly terminate the signal by matching the source impedance (75 ohm in this case) you will get less noise. https://en.wikipedia.org/wiki/Impedance_matching
I bought a BNC T-adapter and a 75 ohm plug. Connected the T-adapter to the scope and each of the female connectors on the T-adapter to the source and a 75 ohm terminal plug. Works great.
Still dont know if the original camera was damaged from the initial method though.
The right way is to terminate the signal with something like a TV or a 75 ohm terminal plug. You want the scope to tap into the signal on its way to its normal destination.
If you just send the composite signal straight to the scope you will suffer from high amounts of noise caused by the signal reflecting against the scopes 1 M ohm wall of resistance. The reflection is visualized well in this video (https://www.youtube.com/watch?v=AjzBGC4tGTo). The waves bouncing back becomes noise.
If you properly terminate the signal by matching the source impedance (75 ohm in this case) you will get less noise. https://en.wikipedia.org/wiki/Impedance_matching
I bought a BNC T-adapter and a 75 ohm plug. Connected the T-adapter to the scope and each of the female connectors on the T-adapter to the source and a 75 ohm terminal plug. Works great.
Still dont know if the original camera was damaged from the initial method though.