Hi,
I am using DSA91304A and have two questions about it.
1. Now we only use Channel 4, but if the Autoscale button is pressed, Channel 1 will be activated, but there is no signal in Channel 1.
2. The meaning of the button Autoscale under Trigger. As far as I understand this button means that the trigger condition will be determined by the osciloscop self and not by the trigger configuration. Is it correct?
Thanks
Owen
I am using DSA91304A and have two questions about it.
1. Now we only use Channel 4, but if the Autoscale button is pressed, Channel 1 will be activated, but there is no signal in Channel 1.
2. The meaning of the button Autoscale under Trigger. As far as I understand this button means that the trigger condition will be determined by the osciloscop self and not by the trigger configuration. Is it correct?
Thanks
Owen
>
> 2. The meaning of the button Autoscale under Trigger. As far as I understand this button means that the trigger condition will be determined by the osciloscop self and not by the trigger configuration. Is it correct?
Autoscale is really for use when you don't know for sure if you have a signals on the various channels, what amplitude, and what frequency they might be at. It replaces 'BeamFinder' from the days of analog scopes.
When connecting to new signals, I almost always press 'Default Setup', followed by 'AutoScale'. Here's approximately what happens:
- The scope looks across all channels to see if there is a signal that is significantly larger than 'noise'. There is an option available under 'Utilities' to only look at channels that are turned on.
- On any channel with a signal, it sets the V/Div so that the signal takes up 80-90% of the vertical on the screen
- It looks to see what channels have obviously periodic characteristics, then sets the sample rate and depth, on all channels, to capture a few periods of the slowest signal.
- It sets the trigger on the rising edge of the highest numbered channel
It can get 'fooled' by a number of things. It doesn't do well with very low-level signals, thinking they are noise. It doesn't do well with Amplitude modulation, like AM, QAM, Radar, etc.
If you don't like the results, you can 'Undo' the AutoScale, and the scope goes back to previous settings.
To your questions:
1. If your scope hasn't been calibrated in a while, the noise, on Channel 1, may have grown enough that the scope is seeing a signal there. If Channel 1 is connected to anything, a cable, wire, or a target, there may be enough signal that it's getting turned on during AutoScale. If nothing is connected, and calibration doesn't fix the problem, then you probably need a repair on the scope.
2. The AutoScale is under the Trigger area, but not part of it. AutoScale does not pay attention to any previous settings, including the trigger. It does save them, so that 'Undo' works, though.
I hope this helps.
Al