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Need help with some measurements.

jw0752

I need some help collecting data about Oscilloscope Probes. I am thinking of making some low frequency Non-Slip probe tip adapters for Oscilloscope probes. With the limited number of Oscilloscope probes with in my reach it does not look like there is any standardization.

 

image

As you can see the two probes that I own each have different diameter probe tips. It would help me plan my project if I could find out what the diameter and length of oscilloscope probes from as many of you as possible. Please measure length of the consistent diameter of the tip and also the diameter itself. I can accept measurement in inches or millimeters. Here is what I hope to be able to build without having to custom make each one.

 

image

 

Your help would be appreciated.

 

John

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  • Hi John,

     

    I'll measure up several later today, and post the results.

    Also, have you considered making the entire 'scope probe? There could perhaps be interest in that.. I'd be interested : )

    There is a brief comment mentioned in 'Art of Electronics' where the profs just use co-ax cable (RG178 in their case) and attach a 953 ohm resistor in series on the end, and it becomes the probe. This then is a X20 probe (and it expects the 'scope end to be set to 50 ohms, or use a T-piece and a 50 ohm terminator for 'scopes that don't have that built-in. This would be good for up to 100-200MHz perhaps, covering many use-cases.. It is mentioned here, in a yellow box:

    https://electronics.stackexchange.com/questions/351368/high-speed-passive-probe-contradiction-between-authors-or-differe…

    Trouble is, a resistor is too flimsy for general probing. Maybe it would be nice to have a complete probe with the co-ax, resistor, and your probe attached.

  • in reply to shabaz

    Hi Shabaz,

     

    I haven't considered it as I felt that there needed to be physical tuning that I wasn't capable of. My partner in the Non-Slip probe adventure Neil asked me today about making Oscilloscope probes and so I thought that perhaps I could make adapter tips for probes that would not be a problem at lower frequencies. That is what got this inquiry started. I have gotten so spoiled using the meter non-slip probes that every time I use my oscilloscope probe I get real frustrated with keeping the probe point where I want it. Since I am pretty much a low frequency tech I decided to make a set of adapter tips for my scopes. When I found the probes had different diameter pins I suspected that there wasn't  a standard size like there is for the meter probes. Now I am collecting data just to see how bad the dis-uniformity really is.

     

    John

  • in reply to jw0752

    , for low frequencies, I use a converter, and then normal DMM probes with your anti-slip points.

    image

    When you build add-ons for oscilloscope probes, there's a whatch out apart from different size of probes:

    the tips are delicate, so the insertion power has to be low and the grip power high enough so that the extension does't cause stress on the probe point.

  • in reply to jw0752

    Hi John,

     

    I think you're right, some tuning at the probe end may be needed for high frequencies. I think maybe it would be adequate for 100-200MHz with no tweaks, but I've not attempted it. I've been meaning to try it for ages, I bought the 953 ohm resistor in a couple of sizes and suitable coax/connector a while back. I'll give it a shot in the next week or two, perhaps that could be engineered into a product with your probe on the end, if you can find a way to construct it.

    Plus, using the 50 ohm termination means no need for any tuning at the 'scope connector end at all.

  • in reply to Jan Cumps

    Hi Jan,

    I think that you have the right approach. So far everything about building adapters specific for scope probes looks problematic. Your point about stress on the existing probe tip is well taken. Tips that are 4 mm long and 1 mm wide do not provide sufficient support structure for addition of a potential lever arm in the form of an adapter. I must get myself one of those adapters.

    John

  • in reply to shabaz

    Hi Shabaz,

     

    I look forward to the results of your build.

     

    John

  • in reply to jw0752

    w2aew - a field engineer of Tektronix - has made nice videos on (among other interesting subjects)  probing techniques.

    I use this one at times when direct probing with the pig tail ground is not enough or not practical:

  • in reply to Jan Cumps

    Hi Jan,

     

    Thanks for the video. It is an excellent idea and I am sure it will be of utility. I will do some experimenting with it tonight.

     

    John

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