Author Topic: Playing with Probes: Guessing game.  (Read 3967 times)

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Offline BillyOTopic starter

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Playing with Probes: Guessing game.
« on: March 04, 2023, 02:14:14 am »
I had a meeting moved yesterday so had a few unstructured/unplanned minutes on my hands to burn.

I broke out the Bodnar pulser and my SDS2000XP and started testing scope probes.

Here are the results of 9 different probes I had lying about.  Each was properly compensated before testing,  Each was attached to the pulser through a 50 ohm feedthrough load and an appropriately sized probe-BNC adapter.

I will update this post with which probe is which at a later time.

In the meantime your mission, should you choose to accept it, is to decide which is the most expensive probe and which is the cheapest.  The price range is approximately $6 to $600 (when new).

They are in the order they came to hand...

Update (prices are Canadian $):
  • UNI-T - UT-P04 - 100MHz - $20
  • Siglent - PP-215 - 200MHz - $54
  • Hantek - PP-300 - 300MHz - $25
  • Pico - TA-386 - 200MHz - $54
  • No Name - P6139A - 500MHz - $42
  • Tektronix - P6139A - 500MHz - $600 (est.)
  • Hantek - PP90 - 80MHz - $6
  • Siglent - PP510 - 100MHz - $40
  • Instrustar - P2060 - 60MHz - $7

I am quite impressed with #4, the Pico probe.  Not the fastest rise time, but it seems well behaved otherwise.  Some things that count against it are that it is a big probe, not re-buildable, no HF compensation and the compensation adjustment is in the probe itself (which probably helps make it so large).

For #9, I'm sure the risetime measurement is being thrown off by the huge overshoot.  It is the worst quality probe I have ever held.
« Last Edit: March 04, 2023, 04:41:20 pm by BillyO »
Bill  (Currently a Siglent fanboy)
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Online tautech

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Re: Playing with Probes: Guessing game.
« Reply #1 on: March 04, 2023, 02:19:15 am »
Each was properly compensated before testing,.............. 
LF/1kHz scope source ?
No HF compensation/adjustment ?
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Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #2 on: March 04, 2023, 02:32:05 am »
The 1KHz source was the SDS2000XP compensation output.

Not having the HF compensation specs nor having access to the innards of all the probes, no special HF compensation was performed for most of them.  That should have been done at the factory.  Only one probe had the HF compensation checked and it was correct.  That was the $600 probe.
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Offline lugaw

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Re: Playing with Probes: Guessing game.
« Reply #3 on: March 04, 2023, 02:45:40 am »
Each was properly compensated before testing,.............. 
LF/1kHz scope source ?
No HF compensation/adjustment ?

How do you do HF compensation adjustment?
 

Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #4 on: March 04, 2023, 02:53:44 am »
How do you do HF compensation adjustment?
Some high quality (read expensive) probes have HF compensation adjustments internally.  You have to be able to take them apart to do the job and the specs/process have to be published.  Better Tektronix probes fall into this category.
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Re: Playing with Probes: Guessing game.
« Reply #5 on: March 04, 2023, 07:40:32 am »
How do you do HF compensation adjustment?
Some high quality (read expensive) probes have HF compensation adjustments internally.  You have to be able to take them apart to do the job and the specs/process have to be published.  Better Tektronix probes fall into this category.
Well no.
Based on what I said in reply #5:
https://www.eevblog.com/forum/testgear/probe-into-probes-whats-up/
All the 500 MHz probes I have ever seen have external HF trimmers and normally 2, both sealed with a plastic cap easily removed with a blade, not too sharp that might slice the plastic cap in half.

Typically with these 500 MHz probes a 1 MHz rising edge of 1ns or better is specified and tweaking of dual trimmers....yes there are 2 in order to get the best step response and with NO overshoot !

Here is where I run into trouble, why on earth not use the Bodnar pulser as a HF edge for adjusting HF step response, it's certainly faster that 1ns and at 10 MHz instead of a specified 1 MHz, why could that matter one damn ?
How might we realistically accomplish these adjustments noting that when the Bodnar pulser is connected directly to a scope there certainly is overshoot....something we would normally trim out when compensating a probe.
In my view and please correct me if you know otherwise, we should attempt to replicate the Bodnar step response when connected directly to a scope when making HF probe adjustments which flies directly in the face of HF trimming out of all overshoot. Interesting dilemma IMO.

We can see some of Bill's probes are in need of HF step response adjustment and based on what I learnt in Bill's probe-into-probes-whats-up thread I would pick probe 5 or 8 as his most expensive and 9 the cheapest......but I've been known to be wrong before !  :horse:

Adjustment instructions for Siglent SP3050A 500 MHz probe attached.
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Offline jonpaul

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Re: Playing with Probes: Guessing game.
« Reply #6 on: March 04, 2023, 12:06:38 pm »
good electronic engineering, no guessing involved.

First read and learn about Oscilloscope Probes, then about ringing in return circuits and terminations.

Highly recommend

Tektronix Circuits Concept book
Oscilloscope Probe Circuits
Probe Measurements
http://www.davmar.org/TE/TekConcepts/

We use Tektronix probes

P6136 Zo
P6137 10x

Never had any issues.
No adjustments except the usual scope input capacity comp
That is always at 1khz as only affects low I tilt

Bon Soirée

Jon
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Offline mawyatt

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Re: Playing with Probes: Guessing game.
« Reply #7 on: March 04, 2023, 02:53:10 pm »
With all the discussions about the Tektronix Trade Secret "T-Coil" going on here.

https://www.eevblog.com/forum/projects/wideband-modern-low-noise-analog-front-ends/25/

This raised the question did Tek utilize the T-Coil in any passive voltage scope probes to improve bandwidth? The answer is yes, and they even used it in some current probes!!!

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #8 on: March 04, 2023, 04:23:23 pm »
Adjustment instructions for Siglent SP3050A 500 MHz probe attached.

That's nice to see.  A lot of probes do not have any way to adjust them.  The Tek P6139A does, but it requires partial dismantling to do it.

I daresay that most sub $100 probes don't have any accessible adjustment and sub $50 probes probably have none at all.

Kudos to Rob for taking a shot at it.  I'll update the first post with the information.
Bill  (Currently a Siglent fanboy)
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Offline jonpaul

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Re: Playing with Probes: Guessing game.
« Reply #9 on: March 04, 2023, 04:47:11 pm »
scope waves show ground wire ringing.

USE BNC adapter or bayonet tip, no ground wire

j
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Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #10 on: March 04, 2023, 04:48:37 pm »
BNC adapters were used.  Ground wires were removed.

The ones with the least ringing are the Siglent probes.


« Last Edit: March 04, 2023, 05:02:36 pm by BillyO »
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Re: Playing with Probes: Guessing game.
« Reply #11 on: March 04, 2023, 08:05:57 pm »
Here's an example of 2 quality (read $) passive probes compared against the Bodnar pulser waveform captured and used as a Ref waveform, plugged directly to scope and 50 Ohm input engaged.



These probes were NIB but their HF response needed adjusting.
If we are to follow the HF adjustment instructions to the letter and use the fast edge of the Bondar pulser, in my view the probe step response need match the Ref waveform as well as is possible.

One of the above adjusted for best/cleanest step response while preserving some overshoot to best match a 50 Ohm connection.


BNC adapters were used.  Ground wires were removed.
Same ^^^^

The ones with the least ringing are the Siglent probes.
As expected.
Based on what I believe you have they will be PP510 and PP215, 100 and 200 MHz passive probes certainly without sufficient BW to resolve the edge speed and overshoot of a Bodnar pulser.
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Offline jonpaul

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Re: Playing with Probes: Guessing game.
« Reply #12 on: March 04, 2023, 09:29:04 pm »
Nice, any test with 400..500 MHz probes on 1 ghz BW scope ?
Test with Zo probes in 50 ohm env ?
Test with ghz FET probe?
j
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Online tautech

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Re: Playing with Probes: Guessing game.
« Reply #13 on: March 05, 2023, 08:14:53 am »
Nice, any test with 400..500 MHz probes on 1 ghz BW scope ?
Test with ghz FET probe?
Done in that previous thread Jon, SDS6204A (2 GHz) used in all tests.
https://www.eevblog.com/forum/testgear/probe-into-probes-whats-up/msg4678768/#msg4678768
https://www.eevblog.com/forum/testgear/probe-into-probes-whats-up/msg4684580/#msg4684580
Test with Zo probes in 50 ohm env ?
Sorry, don't possess one and never had the need.
Instead 100x and 1000x and active and differential probes have met my needs......that change daily....today it was 4hrs driving a tractor for my son.
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Offline jonpaul

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Re: Playing with Probes: Guessing game.
« Reply #14 on: March 05, 2023, 01:37:49 pm »
Rebonjour

Interesting to compare your probe responses to a zero cost, low L ghz Zo...

Précision 50 Ohm BNC coax>>> 450 or 4950 Ohm film or carbon comp 1/4 W resistance >>probe 50 ohm sources
very short shield to ckt rtn to minimize Lser

The result is a Zo  probe zero,cost very wideband low abberation
the series 450 Ohm is 10x. The 4950 Ohm is,100x.

This is similair to Tektronix P6156.

Bon Soirée

Jon



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Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #15 on: March 05, 2023, 03:10:51 pm »
Interesting to compare your probe responses to a zero cost, low L ghz Zo...
I have a home made Z0 probe, but it's not made with very good cable.  I guess I could try to make another.
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Offline jonpaul

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Re: Playing with Probes: Guessing game.
« Reply #16 on: March 05, 2023, 03:51:30 pm »
For a Zo probe, the BW and pulse abberation, transients response is of course à function of the cable impedance , discontinuility, legnth.

We,have,used Belden RG174 /U thin coax, 30..60cml.

The best cables  are very WB coax like Belden 1694.

Tektronix made 50 cm précision 50 ohm coax BNC

See tektronix probe circuit books
http://www.davmar.org/concepts.html
and Belden Cable app notes,and specs.

Jon



 
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Offline H3g3m0n

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Re: Playing with Probes: Guessing game.
« Reply #17 on: March 09, 2023, 11:31:57 am »
Anyone know if the Hantek - PP-300 is legit or some knock off?

The Hantek website only lists up to PP-200 and I don't think they have scopes above 250Mhz.

Although they do have PP-250's in some of the screenshots of the 250Mhz scopes so maybe they just haven't updated it.
 

Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #18 on: March 09, 2023, 05:07:12 pm »
Anyone know if the Hantek - PP-300 is legit or some knock off?
I ordered mine off Amazon.ca.  They came in exactly the same packaging as the probes I got with my Hantek USB scope.  None of them have Hantek written on them or on the "documentation" that came in the pouches.  If you ask me I think Hantek just buy whatever from whoever.  I don't think they make probes.

https://www.amazon.ca/gp/product/B07P6DWRLZ
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Offline H3g3m0n

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Re: Playing with Probes: Guessing game.
« Reply #19 on: March 11, 2023, 12:28:55 am »
They came in exactly the same packaging as the probes I got with my Hantek USB scope.  None of them have Hantek written on them or on the "documentation" that came in the pouches.

The PP-150 I got with my DSO2C10 does have Hantek written on the documentation, the documentation covers PP-80/150/200. But the probe itself just has PP-150 on the sticker, no Hantek branding.

It's also a gray version (Hantek lists PP-XX0 and PP-XX0B with the B being the black version's). My one didn't come with a grounding spring (intentional as the documentation had no mention of one). I think the higher spec ones, (or maybe the black ones) do come with a grounding spring though. I think 150Mhz DSO2X15's come with black PP-200's since they need more bandwidth.

I recently have ordered a PP-250 from Aliexpress, not yet arrived. I don't really have a good way to test them myself (and don't really have the knowledge). I'll see if there is any branding or not (not that really means much coming from Aliexpress).

If you ask me I think Hantek just buy whatever from whoever.  I don't think they make probes.

Wouldn't surprise me.

But I would be skeptical about a cheap unbranded PP-300 probe really being 300Mhz though. They might all be PP-60's rebranded and sold at different price points.

 

Offline BillyOTopic starter

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Re: Playing with Probes: Guessing game.
« Reply #20 on: March 11, 2023, 02:45:38 am »
The PP-90s I got with my 6074BC were grey too.  They also did not come with the ground springs.

The PP-300s I got for my SDS1204X-E (well, "improved" SDS1104X-E) are black and did come with the spring grounds.

However, I'm not too impressed with the overshoot on them and there is no way to adjust it.  I recently got 6 of the Pico TA-386 probes for $10 each from a surplus seller.  They are a pretty big probe but I'm really impressed with their performance and I may just get another 4 of them for the little Siglent to replace the PP-300s.
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Offline H3g3m0n

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Re: Playing with Probes: Guessing game.
« Reply #21 on: March 17, 2023, 05:55:59 am »
My supposed 'Hantek PP-250' arrived. No Hantek branding on the documentation, documentation mentions PP/250 and PP-300. Black with ground spring.

The punchline is they sent it wrapped in cardboard to protected it. Specifically the back of a box for a UNI-T P05 probe. A probe that looks exactly the same as the PP-250 I received except for the sticker on the connector with the model number.

Although it's a 200Mhz probe, not at 250Mhz one. (I only really need 150Mhz so I'm fine).

So I suspect that is probably what the PP-300 listed above is as well.

Of course there's a good change they might be the same source that Hantek is using anyway. The PP-250's pictured on the Hantek site look exactly the same as the UNI-T ones. Although Uni-T doesn't make a passive 250Mhz probe closest are the UT-05 200Mhz and and UT-06 300Mhz probes so unless they made a custom order they are shipping below spec probes.

From my limited testing the rise looks much the same on both the grey PP-150 that came with the scope and the 'PP-250' I ordered from Aliexpress. The PP-250 does show more dips and rises not sure if that's the increased resolution or it causing increased noise.

I recently got 6 of the Pico TA-386 probes for $10 each from a surplus seller.

Nice, those are like $65 AUD each.
 

Offline bailliemccreight92

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Re: Playing with Probes: Guessing game.
« Reply #22 on: March 24, 2023, 02:37:22 pm »
Interesting to compare your probe responses to a zero cost, low L ghz Zo...
I have a home made Z0 probe, but it's not made with very good cable.  I guess I could try to make another.

You should change them, I also had bad wiring, because of them it shows me wrong data... By the way this was the cause why I lost several times here [spam link removed] because I didn't have the correct data and this interac casinos got that tricking me, but since I did this procedure - everything works fine and I am satisfied with it.
« Last Edit: July 25, 2024, 07:56:12 am by Halcyon »
 

Offline Akutchand10

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Re: Playing with Probes: Guessing game.
« Reply #23 on: June 29, 2023, 08:38:49 am »
Thanks for the information!
 
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