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Probe into probes. What's up?

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I recently received an inexpensive ($36) no-name 500MHz probe I got of Amazon (called a P-6139A of all things)and I thought I'd compare it to some other probes I have arornd here including my genuine Tek 6139A probes.

First off, the probe seem very well made.  The cable is very flexible (even more so than the Tek probes), the compensation/BNC housing is metal and it has the 10:1 auto-select pin.  The BNC fist my Siglent scopes and Tek very snugly and the accessories all seem to work very well.  Construction is modeled after the Tek probe with the insulating sleeve going all the way to the probe tip and unscrewing in a similar way to the Tek.  The tip does not unscrew from teh cables assembly though.  It's rated a 300V CAT II and 9pf @ 10Mohm.

In any case, using the Bodnar pulser and my own 1.2ns pulser I did some rise time trials with it, the Tek 6139A and a Hantek PP300 (300MHz probe).  The results have me a bit puzzled.

The first two screen shots are of my and the Bodnar pulsers feeding directly into the "improved" SDS2104XP scope.  In both cases we can see a fairly nice and consistent square wave.

Next 2 are the Hantek PP300.  This is about what I'd expect for this $20 probe.  Actually pretty nice for the price.

Nest 2 are the Tek 6139A.  WTF?  while the initial part of the leading edge is sharp and fast, something goes awfully wrong about 65% of the way up.  Does anyone have idea what this is about?  I get the exact same result from the other two Tek 6139A probes I have here.

The next two are no name P-6139A.  The result with the Bdonar pulser is almost identical to the Tek probe!  Again, what's going on?  The result with my pulser is also weird but could be due to soem interaction between the pulser and the probe.  It still starts out okay, but seems to give up steam before the Tek probe does.

I honestly expected a that at least the Tek probe woudl do better than this and I can't explain why the faster probes behave this way.  Any ideas?

The rest of the screen shots...


--- Quote from: BillyO on January 31, 2023, 07:31:02 pm ---Any ideas?

--- End quote ---

Group delay...have a close look at the Tek 6139A datasheet.

Edit:  are your screenshots labelled correctly? 


Also Tektronix Circuits Concepts book Oscilloscope Probe Circuits
Oscilloscope Probe Measurements

Any scopes avail as second test besides the Chinese?

Any photo of test setup? Block/schema?

Your Probes uses bayonet/BNC adapter or just ordinary ground cable/alligator?

The self inductance of the ground return can affect transient resp, ringing, etc.

We found P6139 rather delicate and use mostly P6137 x10 and P6136 Zo probes on our TEK 2465/P2467B

These probes are fine on Yokogawa digital scopes DL7440, 1740.



--- Quote from: bdunham7 on January 31, 2023, 07:38:36 pm ---Edit:  are your screenshots labelled correctly? 

--- End quote ---
Yes.  Why?


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