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#2509826 - 02/12/16 12:14 PM Role of each sensor in a triple sensor system
mezzopiano Offline
Junior Member

Registered: 11/15/15
Posts: 13
Split from http://www.pianoworld.com/forum/ubbthrea...tml#Post2508986

Originally Posted By Frédéric L
Originally Posted By mezzopiano
Thinking about it some more, I actually wonder whether in a triple sensor system, they use the third (middle) sensor to get a better representation of the final instantaneous speed in addition to the "original" use of it for fast trills or re-pressing a key.

When you repeat a note, only the middle and the bottom sensors are involved. I don't think they use two different way of measuring velocities, then I think the middle sensor is always involved and if it is near the bottom one, the measured velocity is close to an instantaneous velocity.

I started thinking about how each sensor is used in a triple sensor key action on a DP. I understand the concept of re-pressing a key and the use of the middle sensor for that.

However, if in fact only the two bottom sensors are always used to calculate the release speed of the hammer, than what do you need the upper sensor for?

If I depress a key middle-way and stop there, does the action controller calculate the average speed from the two top sensors (because the third sensor didn't sense anything) or just waits until I complete my depress until the end?

I'm a bit confused about the use of each sensor input by the controller in the triple sensor system.

Please don't be afraid to get technical about this, since I'd like to fully understand the specifics.
Many thanks!

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#2509834 - 02/12/16 12:39 PM Re: Role of each sensor in a triple sensor system [Re: mezzopiano]
Frédéric L Online   content
500 Post Club Member

Registered: 10/29/13
Posts: 611
Loc: France
The upper sensor trigger the note-off event (shut off the note).

Then if you trigger a note twice, you don't need to pass the upper sensor and the note is note doesn't shut-off if you release the key between middle and upper sensor.

When triggering a note, the middle sensor start a chronometer, and the bottom sensor trigger a note-on depending of the time spent between the 2 sensors. You need to release the key upper than the middle sensor to trigger a new note because you need to start the chronometer once again.
Yamaha CLP150, Garritan CFX, Ivory II pianos, Galaxy pianos, Native-Instrument The Definitive Piano Collection, Soniccouture Hammersmith, Truekeys, Pianoteq

#2509846 - 02/12/16 01:13 PM Re: Role of each sensor in a triple sensor system [Re: mezzopiano]
spanishbuddha Offline
2000 Post Club Member

Registered: 11/08/09
Posts: 2802
Loc: UK
See the Kawai MP keyboard touch explanation.

#2509938 - 02/12/16 05:23 PM Re: Role of each sensor in a triple sensor system [Re: mezzopiano]
proteal Offline
Full Member

Registered: 08/03/15
Posts: 38
You can understand it as simulating the 3 relevant points in a grand piano: the top sensor controls the string's damper (on/off), the bottom sensor is the escapement point (hammer released toward string), and the middle sensor is the repetition point (where the hammer is re-engaged for a new strike).

Ideally a DP would measure the instantaneous velocity at the bottom sensor, but (for economic reasons I assume) it instead measures the average velocity from middle to bottom. I doubt any DP uses the top sensor at all for velocity calculation, and it could potentially worsen the measurement if it did. For example, it could approximate an acceleration from the 3 points to adjust the velocity calculation, but that would just screw with people who press with non-constant acceleration.


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#2510032 - 02/13/16 01:28 AM Re: Role of each sensor in a triple sensor system [Re: mezzopiano]
mezzopiano Offline
Junior Member

Registered: 11/15/15
Posts: 13
Great explanation! Thanks a lot smile


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