Another interesting example of a dual voice coil motional feedback system from Panasonic around 1968, more about it here
http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=12&t=707
http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=12&t=707
Thanks, very interesting.
Note that the inductance slope of the pickup coil runs opposite to that of the primary driver. When the drive goes out of it's gap, inductance goes down but the pickup goes in deeper, getting higher inductance.
All those switches and choices, too complex for me.
It might tailor the sound I guess, so the owner could play.
My scheme is to try to eliminate the bad stuff by magnetic and pickup design, not to try to do this acceleration or velocity calculation stuff.
Jn
Nice post.
The link, again no reference to the actual physical design of the coils. So not possible to see if it's bifilar or front/back.
I've not found any previous reference to the front/back difference, I suspect nobody's thought of it. I'll keep looking as well.
Ps.. Note their reference to the pickup voltage being velocity dependent. They then have to filter it.
My scheme is not velocity dependent at all. All the velocity information picked up by coil 2 is subtracted from coil 1. The information remaining is only the real component to the drive signal, only signal that is in phase with the voltage.
Jn
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Thanks, that's the kind of simple thing that amuses my simple mind. Some good comments too, I like "So sad when the only left rebel metronome finally align itself"
Fun to watch.
In the clock world, it is called sympathetic vibration. Put two grandfather clocks against the same wall, and eventually they will synchronize.
When troubleshooting a grandfather or grandmother clock, one of the first things to look for is, when it stops, where are the weights? Many times, the case sways ever so gently to the pendulum, and when the weight frequency of oscillation gets close to the pendulums natural frequency, weight sway will take energy from the pendulum. As a clock nears servicing time, the escape wheel/pallet assembly is not receiving enough energy to sustain through that energy loss. Sometimes, just locking the case to the wall near the top is sufficient to get a few more years of operation. If the problem is due to lack of oil, those few more years will make the repair more extensive as the steel pivots will wear a channel in the brass plate.
Some scientists recently did a paper on this sympathetic vibration. Of course, the clock world has known about it for several hundred years.
Jn
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@DPH,
I agree; actually that somebody could repeat the measurement (noise source and sine combined via power mixer), was what i hoped for (as stated before).
That something is always disputable is just normal, no perfect experiment thinkable; i thought it is interesting as the result of that measurement is not compatible with the statement that the device is just an ordinary resistor (small value) .
@ jneutron,
Sure; "baseline" with respect to the measurement equipment would be result of the calibration procedure along with the uncertainty and so a measured internal connection between generator section and analyzer section.
Experimentwise "baseline" is imo what he described as the external connection between generator section and analyzer section via coaxial cable without devices and then with devices installed.
Agreed that the implementation of the devices and comparison conditions are crucial and that it would be much better to have some pics of the "fixture/installation" .
Same procedure we follow.
Btw, i remember a discussion about the Meyer/Moran experiment over at hydrogenaud.io, where i mentioned that measuring the test equipment before and during the experiment (all the more in that case of a long term experiment) is very important - even dared to mention a lab notebook - i was strongly attacked for "rasing the bar to high" and being only interested in discrediting "blind tests" .....
Again agreed, but the lab lists the measurement limits and uncertainty for their equipment on the website
Overall it could be that the actual lab report contained a lot more pages, but that it would be too much for the magazine to print the full report.
Sure.
@gpauk,
As said before, it could be.
Otoh in this case the situation is a bit different, as the quy who did the measurements is actually the owner of the lab, seem to know (from what i´ve read from him) what he is talking about, has some examples of carefully done stuff.
There surely is a slight impression of a nerd factor in there but also surely he isn´t just an ordinary technician being lost due to lack of understanding.
But as said before, it´s just speculation/assumption.....
I agree; actually that somebody could repeat the measurement (noise source and sine combined via power mixer), was what i hoped for (as stated before).
That something is always disputable is just normal, no perfect experiment thinkable; i thought it is interesting as the result of that measurement is not compatible with the statement that the device is just an ordinary resistor (small value) .
@ jneutron,
Sure; "baseline" with respect to the measurement equipment would be result of the calibration procedure along with the uncertainty and so a measured internal connection between generator section and analyzer section.
Experimentwise "baseline" is imo what he described as the external connection between generator section and analyzer section via coaxial cable without devices and then with devices installed.
Agreed that the implementation of the devices and comparison conditions are crucial and that it would be much better to have some pics of the "fixture/installation" .
Same procedure we follow.
Btw, i remember a discussion about the Meyer/Moran experiment over at hydrogenaud.io, where i mentioned that measuring the test equipment before and during the experiment (all the more in that case of a long term experiment) is very important - even dared to mention a lab notebook
- i was strongly attacked for "rasing the bar to high" and being only interested in discrediting "blind tests" .....Again agreed, but the lab lists the measurement limits and uncertainty for their equipment on the website
Overall it could be that the actual lab report contained a lot more pages, but that it would be too much for the magazine to print the full report.
Sure.
@gpauk,
As said before, it could be.
Otoh in this case the situation is a bit different, as the quy who did the measurements is actually the owner of the lab, seem to know (from what i´ve read from him) what he is talking about, has some examples of carefully done stuff.
There surely is a slight impression of a nerd factor in there but also surely he isn´t just an ordinary technician being lost due to lack of understanding.
But as said before, it´s just speculation/assumption.....
Okay, Im starting to understand what your're trying to achieve.
Just thinking out aloud, multiband vehicle mobile phone antenna's use printed inductors (akin to RF striplines) on plastic, the plastic being quite thin could almost wrap around the existing voice coil.
You could print the inductor in any shape you like, i guess the limitation is would this generate enough inductance ?
I had a lady friend who was in a small amateur ensemble and she told me how strange the scoring was for stuff like this.
Yes, that can confirm the equipment capability. But as we know, many times the exact setup, cables, connectors, can impact the end result, especially down near the mud.
One guy here is trying to get good readings with a nano-voltmeter...he has found the learning curve is quite steep.
One question...why are they comparing a resistive device to a wire??? Wouldn't it be better to compare a resistive device with a resistor? We already know that a resistor is different from a wire..
Agreed that the implementation of the devices and comparison conditions are crucial and that it would be much better to have some pics of the "fixture/installation" .
even dared to mention a lab notebook
How dare you. What were you thinking??
sigh...
What's that??? I've never heard of that before, especially in reference to me...
jn
Absolutely..The print can be finer than the vc wire, it can be matched to number of turns.
I recall mentioning that in a thread, not sure where, perhaps months ago. I've seen many Kapton based flexible circuits out there. The problem is, I'm not sure how easy it would be to print on a cylinder, a simple print would require a significant number of connections in there in order to wrap around the coil. If the turns do not wrap around the center pole, it will not be sensitive to the variation of inductance the actual vc sees.
I had spoken about printed loops on the vc former, but the intent back then was to monitor the gap flux or lack thereof. My newer scheme automatically compensates for the variation in vc inductance through the entire vc travel range, the old concept only measured the flux falloff and would require significant DSP to understand how to predistort as it would still require calculation of position and then a lookup table/polynomial fit to apply the compensation distortion. My newer concept will not adjust to flux falloff if the coil leaves the gap.
jn
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Same with a group of these :
Amazon.com: Bulk 5 Pack Solar Powered Dancing Desktop Figurines: Toys & Games
On my Wife's dashboard
No, sorry.(they talk to each other. many times, they say bad things about your driving skills, your taste in clothing, your choice in music...) but don't say that out loud in the car, they tend to gang up.
And they do it just like baby Groot in the final scene of GOTG 1 (the talking amongst themselves I mean..)
jn
And they do it just like baby Groot in the final scene of GOTG 1 (the talking amongst themselves I mean..)
jn
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