As? a non-EE, maybe my take on this could be useful, because the OP was looking for a non-technical analogy or explanation. But it should still be accurate.
The kids going into the house example does not work because the kids are the input - they are already noisy, so negative feedback that compares input to output would not eliminate it. Another way to say it is: nice quiet kids come into the house, other kids already in there yell at them and makes the once-quiet house noisy. The dad asks the noisy kids to stop and be just like the quiet kids, and the house stays quiet.
I don't think this is such a simple, easy analogy, but it seems more accurate (the feedback is not truly instantaneous, for one thing). The key is that negative feedback makes a comparison between input and output, and subtracts what is not in the input.
Unteaching is very difficult - as a researcher dealing with managers, I deal with that almost everyday.
I hope I was gentle enough.
toggle quoted message
Show quoted text
On 3/23/2021 7:04 AM, Keith wrote:
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
