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Re: Testing Scope Probes

 

There's a nice app note about probe impedance and using them by HP:

It has a comparison of tek and HP probes that does not include the 10073C, but shows the concepts with examples and charts...all for up to 100MHz only.

The case for 500MHz is just shifted in all the cases and charts.

It IS tricky.
Re: Testing Scope Probes

 

Honestly Jinxie, you did. That is why you started asking
questions. If everything looked right to you, you wouldn't
have thought a thought about it.

-Chuck Harris


On Wed, 10 Apr 2024 05:56:03 -0700 "Jinxie via groups.io"
<paul666@...> wrote:
Gosh! Who'd a thought testing a passive probe could be so tricky?
Re: Testing Scope Probes

 

You can try the T piece method as long as you accept that it won't actually demonstrate the expected bandwidth of the probe. It will show differences between the probes.

You will have to be wary of any differences that you do see because more output on one probe up at VHF/UHF doesn't always mean it's 'better'. A cheap and basic x10 10Meg scope probe may well show 'over compensation' up at V/UHF when correctly compensated at lower frequencies. What makes the 10073C a class apart is that it has been designed as a 2.2Meg probe and this makes it easier to achieve flat compensation over a wide bandwidth compared to cheaper 10M probes.

A cheaper 10M probe may well show excess peaking on a risetime test for example. Other spurious responses may appear after the peak on a risetime test. If you then compare using the sig gen method you might reach a different conclusion. You might think the cheaper probe is better, but it almost certainly won't have the (more) consistent compensation of the 10073C. The 10073C isn't perfect by any means, but it should outperform the lower cost probes. A risetime test is a good thing to try as it can show up issues with how well damped and compensated the probe is.
Ideally, you would need a really good pulse generator for this and a suitable test fixture.?
Re: HP/Symmetricom 58531A GPS Timing Receiver Analysis & Control software

 

Thanks, Robert.

When I have the time to jump through all of Microchip's hoops I will investigate.

Greg
Re: Testing Scope Probes

 

Perhaps I can combine elements of the best methodology from posters here to get the best results. The thing I'm concerned about with using T adaptors is I don't know what they're specified to. I've got a box with several of them but for all I know they might only be good for a couple of megs! That's why I thought your idea of using stripline had some merit.
Re: Anyone with a 3586B A80 board?

 

FYI - I got the mainboard off the unit last night.? For those who may have this issue in the future, it is possible to get this board off without removing all of the cards.? You do have to remove the front panel and the front panel frame member.
It doesn't look too bad - as in, I've seen worse.? I don't see any damaged traces, and that's a good thing too - this appears to be a 3-layer board.
It appears the worst part of the damage is to the holes in the board where the power supply electrolytic cans' vents peek through - and that's good because there isn't any power flowing through there.? I guess the electrolyte flowed out of the bottom in this area since it's the closest "hole" that didn't have something going through it, plugging it.

Time to order a connector...
Re: Testing Scope Probes

 

Please define the 'known good probe' in your test setup? Does Jinxie have one?
I thought the aim of the exercise was to demonstrate the BW of the ebay probe. If you put two probes in parallel and drive them from a 50R source and a BNC T piece you will end up with an RC time constant of 50R and about 28pF if you include the unwelcome capacitance of the T piece.

So that's why I think you will be lucky to see 150MHz bandwidth with that setup. That could be confusing unless you explain that the setup is obviously flawed in this respect.
Re: HP 05315-60007

 

It is the optioal 10MHz TCXO for the HP 5315 Counter. It's covered in the service data.

On Wed, Apr 10, 2024 at 9:55?AM Joe White <skinnershorse@...> wrote:
What device(s) was this oscillator made for?? Is there any documentation for checking whether the board functions correctly?? The board is marked SERIES 1824.
Thanks
--
Joe White
KW4YW

Re: Testing Scope Probes

 

JMR said:
"The problem with trying to do this with two probes in parallel (using a BNC T piece) is that you will end up with double the loading so I'd expect this test method to be doomed to failure if the aim is to see the expected bandwidth of the scope + probe. Also, feeding the BNC T directly from a 50R source will just make it even worse. Ideally, the source impedance needs to be quite low. 50R is too high for testing a 500MHz probe.? You could end up seeing a BW of 150MHz rather than the expected BW if you use Robert's method as described. "

That is only true if you are trying to generate a known amplitude to measure. My proposal is to compare two probes. The level at the junction of the T will vary with frequency. However both probes will be measuring the same voltage (assuming constant and near zero, relative to frequency / wavelength, distance to the center of the T).

Any difference between the two measured signals will show how the suspect probe is performing compared to the known good probe.

It would complicate things, but if you know the response of the "good" probe it could be used to normalise (adjust to a known level) the signal generator output. and make an absoulte measurement of the suspect probe.

Robert.
HP 05315-60007

 

What device(s) was this oscillator made for?? Is there any documentation for checking whether the board functions correctly?? The board is marked SERIES 1824.
Thanks
--
Joe White
KW4YW
I/O Interconnect cord on HP8703A

  

Hello,

Does anyone can confirm that the I/O-interconnect cord between the HP8703A and its lightwave test set is the same cord as between an HP8753A and its S parameter test set
HP85046A or between the display processor and the lightwave section of a HP8504B ( cord 08503-60051 )

Thanks
Eric
Re: Testing Scope Probes

 

¿ªÔÆÌåÓý

A passive scope probe is more complex the just a resistor divider. Take a look at the original patent for a scope probe.



Allen Hill
KI4QCK

On Apr 10, 2024, at 9:06?AM, Jim Ford <james.ford@...> wrote:

?
Anyone who has tried to measure one, that's who! ;)? ? ? ? ? ? ?Jim Ford?



Sent from my T-Mobile 4G LTE Device


-------- Original message --------
From: "Jinxie via groups.io" <paul666@...>
Date: 4/10/24 5:56 AM (GMT-08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] Testing Scope Probes

Gosh! Who'd a thought testing a passive probe could be so tricky?

US2883619.pdf
US2883619.pdf

Re: Testing Scope Probes

 

¿ªÔÆÌåÓý

Anyone who has tried to measure one, that's who! ;)? ? ? ? ? ? ?Jim Ford?



Sent from my T-Mobile 4G LTE Device


-------- Original message --------
From: "Jinxie via groups.io" <paul666@...>
Date: 4/10/24 5:56 AM (GMT-08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] Testing Scope Probes

Gosh! Who'd a thought testing a passive probe could be so tricky?

Re: Optiion upgrade HP 8753C/B

 

Just in case this helps someone else I've found it now. My A9 board looks like the one here




And as described in the link, the procedure IS detailed in the service manual for the 8752C on page 123 of the pdf. Why HP couldn't put this information into the 8753C manual is baffling.?
Re: Testing Scope Probes

 

Gosh! Who'd a thought testing a passive probe could be so tricky?
Re: Optiion upgrade HP 8753C/B

 

ok thanks, unfortunately totally different layout to my A9 board. the manual isn't very helpful at all.?
Re: Testing Scope Probes

 

Yes.

The typical instrumentation grade RF source (eg. signal
generator) can be modeled as an ideal voltage source in series
with an ideal 50 ohm resistance (impedance).

It is a desirable condition in the case of a mismatched load in
that it won't reflect reflections from the load back towards the
load.

The thing is, if you measure a typical instrumentation grade
RF source, the only way you will get the source's indicated
output voltage is if the load is exactly 50 ohms impedance.

If the probe presents a high impedance, you will measure
something approaching twice the indicated output voltage of the
RF source.

A typical (non video) transmitter, on the other hand, is an
ideal voltage source, and as such has zero ohms output impedance.

Any reflections heading towards the transmitter, will be reflected
right back towards the load.

Your probe(s) will greatly affect the voltage output of your
signal generator, and render the voltage measurement suspect.

-Chuck Harris


On Wed, 10 Apr 2024 04:43:48 -0700 "jmr via groups.io"
<jmrhzu@...> wrote:
The problem with trying to do this with two probes in parallel (using
a BNC T piece) is that you will end up with double the loading so I'd
expect this test method to be doomed to failure if the aim is to see
the expected bandwidth of the scope + probe. Also, feeding the BNC T
directly from a 50R source will just make it even worse. Ideally, the
source impedance needs to be quite low. 50R is too high for testing a
500MHz probe.? You could end up seeing a BW of 150MHz rather than the
expected BW if you use Robert's method as described.
Re: Optiion upgrade HP 8753C/B

 

I think the A9 CC Jumper is in position E33-E34.

See the picture attached but I am not 100% sure because there were
different A9 CPU boards for those series and they have slightly
different layout.

On 10/04/2024 13:21, vee-dub565 via groups.io wrote:
Do you have the adjustments tab which shows /which /jumper is the A9 CC
jumper ? the manual I have just keeps saying move the A9 CC jumper, but
doesn't actually say anywhere which jumper that is on the A9 board
_._,_._,_

A9 CC Jumper.png

Re: Testing Scope Probes

 

A BNC sleeve is exactly what it sounds like it is.

It fits over the bare probe tip, making a press fit connection
to the inside of a female BNC connector so that you can make a
good, albeit high impedance, RF connection.

If you try to use your probe's ground clip, much beyond the
audio region, you will be mostly measuring how your ground clip
is affected by the signal you want to measure.

-Chuck Harris


On Wed, 10 Apr 2024 00:43:53 -0700 "Jinxie via groups.io"
<paul666@...> wrote:
Sorry - need a bit of clarification here. "BNC adaptor sleeve" - what
is that? Does it fit over the probe tip or something?
Re: Testing Scope Probes

 

The problem with trying to do this with two probes in parallel (using a BNC T piece) is that you will end up with double the loading so I'd expect this test method to be doomed to failure if the aim is to see the expected bandwidth of the scope + probe. Also, feeding the BNC T directly from a 50R source will just make it even worse. Ideally, the source impedance needs to be quite low. 50R is too high for testing a 500MHz probe.? You could end up seeing a BW of 150MHz rather than the expected BW if you use Robert's method as described.?
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