posted
I am learning to use an oscilloscope for my engineering labs. Can anyone explain to me what the probe attenuation setting actually changes? The only obvious effect is that the scope will show 10 times the voltage when you change the setting from 1x to 10x (or is it the other way? I forget...), but I know that changing the probe attenuation setting also changes the bandwidth of the scope. What I don't know is why. My prof couldn't explain it either. I am curious as to what is actually changing both in the probe itself when I flip the switch and also in the scope that would limit the bandwidth to 6 MHz when the 1x probe is used, but allow me to use the full 60 MHz bandwidth when the 10x probe us used. It must be affecting the sample rate, but what else is happening? If it matters, I am using a Tektronix TDS1002.
posted
May be it's because of the voltage divider resistor inside the probe..
The bandwidth is limited by the filter made with the combo capacitor-resistor inside..
You know that a probe wire have a capacitance ... by changing the X10 factor, the resistance at end of the wire change and by the way change the frequency cutoff.. ( RC)
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posted
Look here for a complete description about probes. This is a 48 page pdf file from Tektronix and it has everything you need to know about probes.
Basically the reason why your switchable probe does that is because it is made to function in either 1x or 10x. In order to to this the design has to be compromised which affects the performance. If accuracy is real important it is best to get seperate 1x and 10x probes, since their design can be optimized for a single attenuation.
Posts: 327 | From: Pleasanton & Sacramento Ca | Registered: Dec 2001
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quote:Originally posted by ddstang: Look here for a complete description about probes. This is a 48 page pdf file from Tektronix and it has everything you need to know about probes.
Basically the reason why your switchable probe does that is because it is made to function in either 1x or 10x. In order to to this the design has to be compromised which affects the performance. If accuracy is real important it is best to get seperate 1x and 10x probes, since their design can be optimized for a single attenuation.
Thank you for that link! I skimmed it briefly and learned a lot. I saved it to read more thoroughly later. It amazes me that my prof was completely clueless when he deals with these scopes regularly in his research...
posted
Most people are. I use a scope eveyday and I know I could be a lot more effective.
I've taken classes from Tektronix on signal integrity and scope use, time very well spent.
Posts: 2575 | From: GA | Registered: May 1999
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