Author Topic: Probe into probes. What's up?  (Read 8579 times)

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Offline jonpaul

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Re: Probe into probes. What's up?
« Reply #75 on: February 07, 2023, 12:55:58 am »
yes the ground terminal on the opposite face of the probe body which accepts a standard Tektronix ground lead.

j
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Offline Bud

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Re: Probe into probes. What's up?
« Reply #76 on: February 07, 2023, 01:11:34 am »
Right, so I am wondering if it makes sense to use the ground ring of the tip , instead of the long ground lead.
I guess there is a merit to do this if you use the probe in single ended mode with the second tip shorted because in this case return path goes through it. But for differential measurements I am not sure if connecting ground to tips' rings vs the standard ground lead may make a difference from signal integrity perspective.
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Offline tautech

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Re: Probe into probes. What's up?
« Reply #77 on: February 08, 2023, 08:12:58 am »
Tautech:

Many thanks, good link for the scope.

still do not see any shots at fast sweep, only the 10 nS/div, can you show shots like those references with fine detail at 1 nS..200 pS/div?
Okay, lets examine more closely the Siglent 500 MHz 10x SP3050A response from the Bodnar > Tek 1:1 50 Ohm feedthrough in the 2nd pic in my earlier post.

Looking faster and with some Vertical zoom and Horizontal fixed position.  :)

Right down to 500ps/div and 20mV/div, equivalent of 2mV/div with 1x inputs.

Quote
Be good to do a check of feedthru 50 Ohm BNC/SMA terms, of various brands and ages:  LeoB>>50 Ohm Term>>1 M scope to see the cheges in term VSWR at fast edge.
I only have BNC feedthroughs, most 1:1 and just one Tek 10:1, the brown one in the earlier photos.

I'm instead inclined to do a Through on the VNA where I can push them to 8+ GHz although I only have a SMA Cal kit so can't Cal beyond the N-BNC adapters and I don't possess any high quality BNC cables, only off the shelf 1 GHz rated variety. If I place the 50 Ohm terminations on Port 1 for a S11 SWR and a S21 Through measurements we should have enough to be comfortable in selecting the best and worst for comparing probe response with each of them....will do later if we find time.

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Offline jonpaul

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Re: Probe into probes. What's up?
« Reply #78 on: February 08, 2023, 12:44:05 pm »
If the scope has an internal 50 Ohm input, why do you eed any extenal feedthru?

All of our tests on DL7440, 7104, 78904, 7A29 use only the 50 Ohm inout.

Pluse Gen>>50 Ohm -20 db attn>>scope 50 Ohms.

Unless you test a probe , just  test the scope with no probes.

Jon
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Online BillyOTopic starter

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Re: Probe into probes. What's up?
« Reply #79 on: February 08, 2023, 05:48:34 pm »
Unless you test a probe , just  test the scope with no probes.

Jon
He is demonstrating the probes.
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Offline tautech

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Re: Probe into probes. What's up?
« Reply #80 on: February 08, 2023, 07:44:35 pm »
If the scope has an internal 50 Ohm input, why do you eed any extenal feedthru?

All of our tests on DL7440, 7104, 78904, 7A29 use only the 50 Ohm inout.

Pluse Gen>>50 Ohm -20 db attn>>scope 50 Ohms.

Unless you test a probe , just  test the scope with no probes.

Jon
Done 1yr ago:
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg4032745/#msg4032745
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Offline tautech

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Re: Probe into probes. What's up?
« Reply #81 on: February 09, 2023, 08:04:52 am »
As we were examining probe step response the SWR of 50 Ohm feed through terminations in my probe tests was seen to influence overshoot and a Tek 1:1 termination was selected for tests only in that it seemed to have the least influence.

However this should be properly quantified and as we have the tools  :) why not put all 4 onto our SNA5000A 4 port VNA and sweep them to 2 GHz for a SWR check.

Note the SWR measurements top right at 1 GHz and the 3 different vertical scales used.

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Offline jonpaul

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Re: Probe into probes. What's up?
« Reply #82 on: February 09, 2023, 01:03:46 pm »
Rebonjour a tous....accumulated from Ham Radio fleas, silent key estates, epay.

 The P6046 TEK diff probe collection: Unused for 20 years, just  unearthed.
2 probes 2 amps/PSU, All accessories, incl X10 attn and shorting tips (large gray tips)
The VERY rare probe body housings and special probe CAL housing ( from the late and great Deane KIDD?).

Works fine after a bit of lube on the amp zero control

AMAZING INSTRUMENT Very sensitive very stable.

Issues: Needed fooling with zero DC  adj pot on amps  cleaning of PSU, amps, probe bodies (iso alc)
Case foam going bad
 
Hope to  test CMRR and NM gain vs freq on HP4195A 100k...500 MHz in 50 Ohm environment


Seeking the original printed manual, can offer swaps for other orig TEK printed manuals.


Your feedback appreciated!

Bon Soiree!

Jon
Jean-Paul  the Internet Dinosaur
 


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