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Why is there a difference in trace width between 1x and 10x probe?
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ttodorov:
Hi everyone!

I have a Rigol DS1052Z and I was testing a simple transistor amplifier circuit using my function generator. I have been told to set the oscilloscope probe in 10x mode as to not load and distort the amplifier, which was not buffered.

I noticed that the trace on the oscilloscope screen looked very fat and ugly. So I hooked up 2 channels of the oscilloscope directly to the output of the function generator and took a screenshot to show you. The only difference between the settings is that CH1 is 1x and CH2 is 10x (both in settings and probe switch).

Can anyone explain why the blue trace looks so ugly, and if there is something I can do to fix this?

Thanks!
wasedadoc:
Channel 2 probe's earth clip not attached?
alm:
If you tell the scope you're using a 10x probe, it will amplify the signal a factor 10 more to compensate. So when it displays a sensitivity of 10 mv/div, then this means 10 mv/div at the probe tip, but 1 mv/div at the scope input connector. So you're seeing the noise of the vertical amplifier being set to 1 mv/div for the blue trace in your screenshot.

Basically the reason why 1x probes exist is because they allow higher sensitivity and lower noise for low level signals. At the expense of higher loading and lower bandwidth.
ttodorov:
So there is basically no setting or a better probe that would fix this?
Kleinstein:
Both the x1 and x10 probes have weak points. The x10 probe is more sensitive to noise of the scope input as the signal is divided down.
The x1 probe has more (especially capacitive) loading of the DUT and also usually has a quite limited bandwidth (e.g. 3-10 MHz range).  Much of the background seen with the x10 setting is from fast spikes that are reduced in amplitude by the reduced BW. The reduced BW also reduces the noise, but you of cause miss parts of the signal.

There are also active probes, that may offer a better combination of BW and noise. However these are expensive (more than the cheap scope) and need a special supply that higher end scopes may provide.
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