PSN-L Email List Message

Subject: when feedback is not needed
From: Randall Peters PETERS_RD@..........
Date: Wed, 13 Feb 2008 12:08:23 -0500

Recent discussions of force feedback have mentioned pendulums.  I hope that these were thoughts directed only toward horizontal
instruments of the 'garden gate' variety (not what I call a pendulum); since I can't imagine a reason for ever wanting to go to
that degree of difficulty with a 'simple' pendulum such as in the VolksMeter.  The direction of a simple static pendulum does
not migrate to any great extent.  Its very low frequency response is determined by shape changes of the earth that do not exceed
tens of microradians.  The exception to this claim applies only to the case of a detector with a very limited mechanical dynamic
range, such as a gap varying capacitive sensor.  With the area-varying array used by the VoksMeter it is unlikely that force
balance or any other type of feedback should ever be needed.

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