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 Post subject: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 3:55 am 
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Joined: Nov Sat 24, 2012 5:05 am
Posts: 100
Just picked up my first oscilloscope very reasonably priced, however it did not come with a probe. It is a BK precision model 2120. Do I need a BK probe or will any probe do? Does anyone have a recommendation or where I might find one? Thanks.


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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 4:07 am 
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Joined: Oct Sun 15, 2006 12:57 pm
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Location: Liberty, Missorui
Any probe should do. Scope probes come in various "frequency response" types, just be sure the probe you get is at least the same as the rated frequency response of your scope.

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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 7:48 am 
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Joined: Nov Mon 02, 2009 7:01 am
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Location: Lincoln City, OR
Greetings to ettore and the Forum:

Ideally, if the probe is a compensating type, make sure that its compensation range includes the specified shunt capacity of the scope.

Regards,

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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 9:20 am 
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Joined: Oct Sun 15, 2006 12:57 pm
Posts: 5436
Location: Liberty, Missorui
Quote:
...make sure that its compensation range includes the specified shunt capacity of the scope...
Good point!!

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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 1:28 pm 
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Joined: Nov Sat 24, 2012 5:05 am
Posts: 100
Hey guys thanks for the responses. My scope is 20MHz so would that mean I need a 20MHz probe or a 20MHz or Higher probe. Not really sure what is meant by a compensating probe and determining the shunt capacity of the scope. I see all sorts of 100MHz probes for sale on ebay would one of these work, or is there a better source for a good probe.Anything to avoid or are they all good enough for a radio hobbyist.


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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 3:09 pm 
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Joined: Jan Mon 05, 2009 4:09 am
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Location: Hudson, MA
Here is a link to the manual

https://bkpmedia.s3.amazonaws.com/downl ... manual.pdf

On page 4 it mentions the input capacitance is 35pF, make sure you get a probe that will adjust with this.

This may help:
https://www.youtube.com/watch?v=oxJQr4dKnys

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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 3:52 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
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Location: Annapolis, MD
The typical probe is called "10X", meaning that it attenuates the signal to 1/10 of the input. This means that the input impedance at the point of measurement is 10X higher. With no capacitance, it would be a simple matter of picking the right resistor to put in series. But the real world has capacitance at the input of the scope, which would make the probe act as a low-pass filter. So, the typical 10X probe has a small cap in parallel with the series resistor, thus proving flat frequency response. The cap is adjusted to exactly compensate for the input capacitance of the scope and the probe cable.

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 Post subject: Re: Oscilloscope Probe
PostPosted: Feb Sat 03, 2018 4:34 pm 
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Joined: Nov Sat 24, 2012 5:05 am
Posts: 100
Mark, Eddie,

Thanks for the rapid reply. Will down load the manual and see what I can figure out. I have a friend with a Hitachi scope and I noticed his probe had a switch on it labeled X1, X10 and X100, I think that is what Mark was talking about. Off to the internet, again thanks a million for the help.

Charles


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