Products > Test Equipment
Probe into probes. What's up?
<< < (11/17) > >>
mawyatt:

--- Quote from: David Hess on February 03, 2023, 12:56:13 am ---

Tektronix took advantage of their CCD based sampling technology to make a small and low cost sampling front end for that series of DSOs. 


--- End quote ---

Tek also used their custom CCD semiconductor fab process to produce some of the better CCD imaging chips back then.

Best,
tautech:
Found some time to play.....

All following square wave/step response checks are from one of Leo Bodnar's fine 10 MHz pulsers and in this one's case, a 30ps pulser.
First, the pulser alone into internal 50 Ohm input attenuation in SDS6204A:
(used for later reference trace)


Next is with Siglents SAP1000 active probe on Ch1 with ground spring and tip connected to the back side of the BNC pads on Leo's pulser where we can plainly see even its 1.2pF input capacitance can impact on the fidelity of the pulse.


So with some simple trickery with a reference trace captured as a fidelity reference (leftmost) and pulser on ch4 and active probe on ch1 the propagation delays from the different input paths have all 3 traces nicely staggered for us to easily compare them all.
Edges: Reference trace then Ch4 50 Ohm input to Bodnar pulser and last, ch1 Siglent SAP1000 active probe.


Where to from here ?
Well only a 1 GHz active probe has been used thus far and I have 3 passive probe's step responses yet to check, Siglent 500 MHz SP5050A that comes with SDS6204A, Pintek 500 MHz CP-3501R/pro and Pintek 600 MHz CP-3601R.

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......
jonpaul:
Rebonjour à tous!  Bravo pour Tautron, Very fine work on the Leo B 40 ps.

Years ago we posted some similar results on Tektronix 7104/7A29, 7B10, 7B15, and 2467B, and digital Yokogawa DL7440. ("show us your square wave"?) We tested sans probes, our trusty Leo B 40 ps direct to scope 50 Ohms, with a few setup improvements:

1/Pulser at 10 MHz rate,  Fine transient response shown at faster sweep rates, to the fastest on each scope.
The Tektronix 7104 1 Ghz fastest analog scope is amazing.....

2/ trim of scope ( and plug-in) vertical response  can be optimized for best BW or cleanest transients response. BUT  Not both! Our work in digital audio transmission and wideband transformers required best transients response. the modern  Chinese scopes preffered to optimize first BW specs, not transient abberation.

We have spent many happy hours tweaking fast scope verticale amps for best transients..many interacting trims, some are fragile tiny ceramic disc trimmers, or a few turns nano Hy  coils, not for the faint of heart...

3/Observéd Transient abberation is affected by the pulser and  scope VSWR, due to reflections.
Our old trick is to insert a wideband 20 db passive attenuator between the pulser and the scopes input.
We reccomend Mini-Circuits HAT-20 BNC in-line.  Many Ghz band. The results always show some improvement.   

Textmatic.....
LeoB 40 pS>>>HAT-20 attn>>Scope 50 Ohm input.

https://www.minicircuits.com/WebStore/dashboard.html?model=HAT-20%2B

So, have an Absolutely fantastic day!

Bon Soirée

Jon




bdunham7:

--- 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.

To be continued......

--- End quote ---

Very nice!  Since you have the equipment to show off, perhaps you could demonstrate the effect of probe loading on the actual signal by connecting a passive probe to the pulser as you've shown and then probing the backside with your active probe.  The 1.2pF of the active probe did have a slight effect on the rise time (~30ps or so) of the direct signal, but that was pretty subtle.
tautech:

--- Quote from: jonpaul on February 03, 2023, 10:01:57 am ---Very fine work on the Leo B 40 ps.

--- End quote ---
This one is actually 28ps according to the screenshot provided with it from Leo.


--- Quote ---3/Observéd Transient abberation is affected by the pulser and  scope VSWR, due to reflections.
Our old trick is to insert a wideband 20 db passive attenuator between the pulser and the scopes input.
We recommend Mini-Circuits HAT-20 BNC in-line.  Many Ghz band. The results always show some improvement.   
--- End quote ---
Yes I know these tricks too but......to not get too complex and confuse the readers we have not used one but that is coming.  ;)
For now when we need external termination of the Bodnar pulser a Tek 1x 50 Ohm BNC feedthrough has been used but you've only seen its effects in the last screenshot and it's loaded with 2 passive probes.  ::)
IIRC Tek rated these feedthrough's to 1 GHz and I also have a 10x version that we will later use as a pad but higher input sensitivities will be needed of course but we save this for a later installment only using the 10x pad so to reduce the chance of reader confusion.

For interest I got a new Pintek 1x 50 Ohm BNC feedthrough a couple years back and the VNA indicates it's better than these great old Tek terminations so we might also be comparing how it and the Tek affect the step response waveform.
http://www.pintek.com.tw/customer/pintek/upload/PL-50pro-DM.pdf


--- Quote from: bdunham7 on February 03, 2023, 04:53:56 pm ---
--- 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.

To be continued......

--- End quote ---

Very nice!  Since you have the equipment to show off, perhaps you could demonstrate the effect of probe loading on the actual signal by connecting a passive probe to the pulser as you've shown and then probing the backside with your active probe.  The 1.2pF of the active probe did have a slight effect on the rise time (~30ps or so) of the direct signal, but that was pretty subtle.

--- End quote ---
Yes but worthy of demonstrating as the old adage; every measurement changes the measurement, is very valid when we examine results closely.

As time permits we certainly will look at many more things in detail and maybe even differential probes of which I only carry 25 MHz models to display although their rise times are slow they are quite adequate for many tasks......then there's current probes too which no power engineer shouldn't be without for which a Tek P6021 with passive termination is probably still the best bang for buck if you can find a good one after how many decades in production ?  :scared:
Like Jon I have the 6021 and 6022 < both highly valued pieces of kit.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod