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On Tue, Mar 23, 2021 at 06:51 PM, Raymond Domp Frank wrote:

Ondrej,
Your observations re. B-gate in 1, 2, 5, 10 ns positions are as they

should

be. I guess at positions 5ns/div and faster, it says "A only" on the

front

plate but I guess it actually shows B.

From what I can see in your video, all B-gate times are ok from 1 ns/div
down to 100ns/div. At longer times, B-gate is too long (belonging to 10x
faster B-times).

Raymond

re: Negative Feedback example, etc.

Folks tell me that a gentle answer turns away wrath, so I hope this is a gentle reply. I mean it in that spirit.

Tom, with respect to your criticism of my example, I would suggest that you do a quick review of the original post #1. Here is the pertinent part of it, for your convenience:

Hi all,
I'm trying to explain to people at my company (none of whom are EEs or
statisticians) how negative feedback works in a system. That's one
thing that I'm trying to get across, and I can't come up with an
explanation of it in every day terms. All the examples I find in
biology etc seem kind of dubious and not very straightforward -
there's a lot of "trust me on this" as to why it's actually negative
feedback and not some form of other regulation. What's a simple
/physical/ negative feedback?

This is question 1 in the OP...period. The core of it is simple. "...how negative feedback works in a system..." Only in the next sentence (not quoted above) does the OP then use the word "another", and only then does he bring up a second question about feedback and noise. So, the original post is really two questions. Question 1 is the issue of a real world example of negative feedback in a system. Question 2 is the interaction of feedback and noise.

Nothing in my example is intended or stated to address that second question. I had nothing to add to that discussion, and so attempted to provide the OP with his example for question one. Now I admit that the use of the word "noise" in my example does unintentionally blur the line - since I say "noisy happy children". I see how that might cause confusion, so I will attempt to edit my post to remove that word. Thanks for that.

But, to be clear here, my example was only intended to apply to question #1 in the OP. Question #1 was the only part for which I felt I had an example that met his requirements, specifically that it be;

1. "non technical" - (which I admit I assumed would mean for persons who have no electronic background)
2. use "everyday terms" (everyday means things that average people from all walks of life could grasp)
3. provide a "simple / physical / negative feedback" example.

Of course every analogy breaks down at some point, but in learning and teaching, it is quite common to go from the simple to the complex in a series of stepped examples - first simple and familiar, and therefore necessarily incomplete at some level. Then more subtle, complex, and therefore more narrow and demanding in proofs and adherence to reality.

Thanks for reading my reply in a mild spirit. I mean no disrespect, but at the moment I stand by my example (modified to remove the word "noisy" of course) as meeting the requirements of OP's question one only. Of course, if you see it differently, then perhaps we'll just have to agree to disagree on this one? In any case, thanks for your contributions to the forum. You're a valuable resource here.

Warmly,

Keith

On Tue, Mar 23, 2021 at 06:51 PM, Raymond Domp Frank wrote:

Observation 'scope (2465B?

Just realised that's a 2467B.....

Raymond

On Tue, Mar 23, 2021 at 09:27 AM, Ondrej Pavelka wrote:

Here is a odd thing I observing with B gate. Is this normal? Basically I
expect the pulse to be shortest at 1nS and gradually widen. What happens
here it basically goes in circles instead.
Looking at the width on your picture my B gate pulse width is correct at
1ns, corect at 2 and 5 but at 10ns us again the same length as 1nS and that
can't be right?

As far as I remember B-gate time stays the same from 1ns to 2ns (because of
the reason I mentioned before) then increases at 5ns. I will look at what
happens on my scope but I expect it should continue increasing.

Ozan

Hi Ondrej,
Videos are very useful.

I was surprised sweep and gate signals are not aligned but I think you are
using different probes for each. Using a BNC cable for all of them will
eliminate any mismatch. Just for reference here is what I had observed:

/g/TekScopes/photo/262059/0?p=Created,,,20,2,0,0
Setup: Inputs were set to 50-ohm (used BNC-T plus termination for CH3). No
signal input, free running.

Raymond's question reminded me my earlier message:

Are you sure B sweep shaft is not rotated out of alignment? You can

look at J1 (relay signal) and check it switches at .1us/.2us boundary.

I read your reply about timebases being locked. You may already know that
but you can pull the time/div knob and rotate clockwise to speed up B
timebase compared to A timebase. In that position B is not locked to A, and
you can check if B can be rotated past the 1ns/div setting. There is a lock
mechanism that won't allow B slower than A, so don't force in that
direction.

I will look at the video again an reply later, I wanted to catch you while
it is still earlier in the evening.
Ozan

Hi Ondrej,
Videos are very useful.

I was surprised sweep and gate signals are not aligned but I think you are
using different probes for each. Using a BNC cable for all of them will
eliminate any mismatch. Just for reference here is what I had observed:

/g/TekScopes/photo/262059/0?p=Created,,,20,2,0,0
Setup: Inputs were set to 50-ohm (used BNC-T plus termination for CH3). No
signal input, free running.

Raymond's question reminded me my earlier message:

Are you sure B sweep shaft is not rotated out of alignment? You can

look at J1 (relay signal) and check it switches at .1us/.2us boundary.

I read your reply about timebases being locked. You may already know that
but you can pull the time/div knob and rotate clockwise to speed up B
timebase compared to A timebase. In that position B is not locked to A, and
you can check if B can be rotated past the 1ns/div setting. There is a lock
mechanism that won't allow B slower than A, so don't force in that
direction.

I will look at the video again an reply later, I wanted to catch you while
it is still earlier in the evening.
Ozan

On Tue, Mar 23, 2021 at 02:04 PM, Ondrej Pavelka wrote:

The time base knob cannot be inserted in any other way. It's all locked

Sorry to insist and no idea whether it matches any of your other symptoms
but on my 485, it's no problem repositioning the knob on its shaft so B
runs 10x as fast as A while A and B knobs are interlocked.

Raymond

re: Negative Feedback example, etc.

Folks tell me that a gentle answer turns away wrath, so I hope this is a gentle reply. I mean it in that spirit.

Tom, with respect to your criticism of my example, I would suggest that you do a quick review of the original post #1. Here is the pertinent part of it, for your convenience:

Hi all,
I'm trying to explain to people at my company (none of whom are EEs or
statisticians) how negative feedback works in a system. That's one
thing that I'm trying to get across, and I can't come up with an
explanation of it in every day terms. All the examples I find in
biology etc seem kind of dubious and not very straightforward -
there's a lot of "trust me on this" as to why it's actually negative
feedback and not some form of other regulation. What's a simple
/physical/ negative feedback?

This is question 1 in the OP...period. The core of it is simple. "...how negative feedback works in a system..." Only in the next sentence (not quoted above) does the OP then use the word "another", and only then does he bring up a second question about feedback and noise. So, the original post is really two questions. Question 1 is the issue of a real world example of negative feedback in a system. Question 2 is the interaction of feedback and noise.

Nothing in my example is intended or stated to address that second question. I had nothing to add to that discussion, and so attempted to provide the OP with his example for question one. Now I admit that the use of the word "noise" in my example does unintentionally blur the line - since I say "noisy happy children". I see how that might cause confusion, so I will attempt to edit my post to remove that word. Thanks for that.

But, to be clear here, my example was only intended to apply to question #1 in the OP. Question #1 was the only part for which I felt I had an example that met his requirements, specifically that it be;

1. "non technical" - (which I admit I assumed would mean for persons who have no electronic background)
2. use "everyday terms" (everyday means things that average people from all walks of life could grasp)
3. provide a "simple / physical / negative feedback" example.

Of course every analogy breaks down at some point, but in learning and teaching, it is quite common to go from the simple to the complex in a series of stepped examples - first simple and familiar, and therefore necessarily incomplete at some level. Then more subtle, complex, and therefore more narrow and demanding in proofs and adherence to reality.

Thanks for reading my reply in a mild spirit. I mean no disrespect, but at the moment I stand by my example (modified to remove the word "noisy" of course) as meeting the requirements of OP's question one only. Of course, if you see it differently, then perhaps we'll just have to agree to disagree on this one? In any case, thanks for your contributions to the forum. You're a valuable resource here.

Warmly,

Keith