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Probe into probes. What's up?

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jonpaul:
Differential probes are by definition active, and with rare exceptions like P6046 TEK, have limited BW.

They have their place esp the HV 4kV CATIII but are not useful in high BW work.

Jon

BillyO:

--- Quote from: jonpaul on February 05, 2023, 02:59:48 pm --- Your thoughts?


Jon

--- End quote ---
There seems to be a reasonable reduction in ringing.

David Hess:

--- Quote from: jonpaul on February 05, 2023, 07:45:45 pm ---Differential probes are by definition active, and with rare exceptions like P6046 TEK, have limited BW.

They have their place esp the HV 4kV CATIII but are not useful in high BW work.
--- End quote ---

The Tektronix P6046 was particularly useful beyond its bandwidth rating because it had useful common mode rejection beyond its bandwidth.

jonpaul:
Rebonjour, David, BillO: Mille mercis pour tes idées et feedbacks.

1/ We used P6046  in 1971..1975  with the Sequerra Tuner at 10.7 and 100 MHz. Entire tuner RF/IF was full differential.
 https://hometheaterreview.com/sequerra-model-1-fm-tuner-reviewed/

2/ We found P6046 was delicate mechanically, electrically and has a thick cable. We made special PCB and test fixtures to mate to the probes inputs.
https://w140.com/tekwiki/wiki/P6046

3/ The max voltage range +/- 25V  is critical as even a sub uSec transient or static can blow the sensitive  probe inputs. Very hard to repair!

"Use the shorting plugs on the tips when not in use:  Ground the probe! Seriously. Sticker the probe "Ground Me!" ."
We always protect the tips with the 10X attn head. That head increases the range to +/- 250V.

4/ As most of our work high speed afterwards was single ended, thus CMRR was not an issue.

5/ All questions re the 120/230V PSU connections, testing, iuse of ground lead are in the manual:
https://w140.com/Tek_P6046_Differential_Probe-Operation_Manual.pdf

6/ By analyzing the measurement requirement and system block, we seldom find a need for the differential probes,  high speed or HV, even  though we have both.
99%of times we use single ended V and current probes.

Being retired, my work is reduced to SMPS/Electronic Ballast (use mains isolation transformer)  digital audio transmission and magnetics,  eg AES/EBU/SP/DIF, baud rate to 24.576 MHz >> BW ! 125 MHz.




Hope this is of interest,

Have an ABSOLUTELY FANTASTIC day!

Jon

PS:   for WB fast work, we use just  a coax to BNC to make a Zo probe or TEK Zo probe  P6136.

10X: Of all the TEK 10X probes accumulated since 1968 (!) the most useful, robust and practical (tips, ground return lead, BW, aberration) we use is P6137, way better than the smaller or larger TEK  series.



 

tautech:

--- Quote from: tautech on February 03, 2023, 09:23:38 am ---.................

This is where things get interesting as we must compare each one by one using the Bodnar pulser terminated into 50 Ohms with the probe tip to BNC adapter for the connection and the probe step response is just what it is....providing LF and HF compensation has been set correctly.

Here we have a teaser with a couple of NIB probes, freshly LF compensated and compared to the reference trace which indicates HF compensation needs also be checked.



To be continued......

--- End quote ---
Continuing
By trial and error the best feed through was found from 3 for the lowest ringing to terminate the Bodnar pulser into for testing HF probe step response. The Tek 1x was the winner with the least overshoot to initially do the HF compensation to a direct BNC connection from the pulser.

Pulser, feedthrough's, Siglent PS3050A 10x and Pintek CP-3501R 10x probe


SAP1000 and Pintek CP-3601R 10x probe


3 passive probes were checked against the Ref waveform captured from the Bodnar pulser into Ch4 input.
Each of these required HF compensation (see above screenshot) for which I used the Bodnar 10 MHz pulser whereas all probe pamphlet instructions state 1 MHz should be used and peaks (overshoot) should be within or no higher than max amplitude.
However I chose on this occasion to best replicate the Ref waveform with all HF adjustments and the results are as follows.
Then a check with the SAP1000 1 GHz active probe on the rear of the pulser BNC with it connected to the termination to check signal fidelity was near to our previously saved Reference waveform. Near enough is the verdict and gives us an indicative risetime of some 340ps to compare passive probe performance against roughly 80ps slower than the direct BNC connection.
SAP1000



Siglent SP3050A 500 MHz 10x sense probe proved the most difficult to perform the HF compensation upon for the following screenshot.



Pintek CP-3601R 600 MHz 10x probe



Pintek CP-3501R 500 MHz 10x probe.




The surprise is the Siglent SP3050A while not providing the best step response did provide what appears to be the slightly better rise times.

Next up are some other probe checks, PP215, a SP2030A we have lying about and a couple more Pintek 10x sense probes, CP3351R and CP3101R and while at it we should also test 100x CP3308R 2kV and 1000x HVP-08 8kV probes.

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