PSN-L Email List Message

Subject: RE: Spring Damping to Chris and John
From: "Paul Cianciolo" Paulc@........
Date: Mon, 23 Jul 2007 19:31:11 -0400


Chris,

Maybe I am making too much out of this problem, but I will try the tiny
neo's and see what happens.

Thanks for giving a push into back into the world of reality.
Plucking the spring is really not a realistic situation.

PauLC


  -----Original Message-----
  From: psn-l-request@.............. [mailto:psn-l-request@.................
Behalf Of ChrisAtUpw@.......
  Sent: Monday, July 23, 2007 6:48 PM
  To: psn-l@..............
  Subject: Re: Spring Damping to Chris and John


  In a message dated 2007/07/23, Paulc@........ writes:


    If I depress the arm say 3/4" on my sensor, the arm will return to zero
position overshoot about 1/2 cycle and return to rest at zero.


  Hi Paul,

         The damping need to set so that if you displace the arm by 10 mm,
it just swings back through the zero position by ~0.5 mm.


    However the suspension spring rings, resonates at a rate of a few hertz,
imparting its resonance on top of the  4 sec period of the sensor.
    This is what I need to stop.


         Maybe increase the spring tension so that it resonates at >10 Hz
and set the low pass filter to reject everything above 5 Hz?


    If the suspension spring on the AS-1 is plucked does it not vibrate at
some frequency and impart that noise into the machine?


         Certainly it will resonate if you do that, but are you really
planning for >M6 local quakes? I would be surprised if you ever saw
significant spring resonance effects. The whole system would need to be
shaken at the resonant frequency, or by a seismic signal which has a rise
time shorter than this. High frequency movements are severely damped. You
can attach tiny cubic NdFeB magnets at points on a spring and mount a copper
plate or tube close to them. This is sometimes done for leaf springs.

         Regards,

         Chris Chapman





Chris,
 
Maybe=20 I am making too much out of this = problem, but I will try=20 the tiny neo's and see what happens.
 
Thanks=20 for giving a push into back into the world of = reality.
Plucking the spring is really not a realistic=20 situation.
 
PauLC
 
 
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of=20 ChrisAtUpw@.......
Sent: Monday, July 23, 2007 6:48=20 PM
To: psn-l@..............
Subject: Re: Spring = Damping to=20 Chris and John

In a message dated 2007/07/23, Paulc@........... writes:

If I depress the arm say 3/4" on my sensor, the arm will = return=20 to zero position overshoot about 1/2 cycle and return to rest at=20 zero.


Hi=20 Paul,
      =20
       The damping need to set so = that if=20 you displace the arm by 10 mm, it just swings back through the zero = position=20 by ~0.5 mm.


However the suspension spring rings, resonates at a rate = of a=20 few hertz, imparting its resonance on top of the  4 sec period of = the=20 sensor.
This is what I need to stop.

       Maybe=20 increase the spring tension so that it resonates at >10 Hz and set = the low=20 pass filter to reject everything above 5 Hz?

If the suspension spring on the AS-1 is plucked does it = not=20 vibrate at some frequency and impart that noise into the=20 machine?

      =20 Certainly it will resonate if you do that, but are you really planning = for=20 >M6 local quakes? I would be surprised if you ever saw significant = spring=20 resonance effects. The whole system would need to be shaken at the = resonant=20 frequency, or by a seismic signal which has a rise time shorter than = this.=20 High frequency movements are severely damped. You can attach tiny = cubic NdFeB=20 magnets at points on a spring and mount a copper plate or tube close = to them.=20 This is sometimes done for leaf springs.=20

      =20 Regards,

       Chris = Chapman
=20

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