PSN-L Email List Message

Subject: Re:AD7142 ?
From: Barry Lotz barry_lotz@.............
Date: Wed, 12 Apr 2006 21:25:34 -0700 (PDT)


Hi Brett
    STM wrote as a solution to LVDTs "The common solution is to use a capacitive bridge transducer, where a moving vane moves between two fixed plates that form a capacitive bridge that is unbalanced by the movement of the vane. With proper geometry, these can be very sensitive and linear over a range of several hundred microns. However, they are difficult to construct and have a working gap of less than a millimeter, and are prone to off axis sensitivity. They usually operate at relatively high frequencies, from khz to mhz, which complicates design and implementation problems" It looks like the AD device would solve some of these concerns. He then goes on to describe the VRDT. I suppose for the VBB sensor this would greatly simplify the electronic design if one can deal with small sensor gaps. I'm not sure about the noise. Does the VBB measure displacements in the 1  nm range?   --- Just thinking out loud. I think it greatly depends on what type of sensing one wants to do
 local,regional or teleseismic. I like the possibility's.
  Regards
  Barry
  

Brett Nordgren  wrote:
  My bad.

Meant to say AD7745 / 7746

Sorry,
Brett


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Hi Brett
  STM wrote as a solution to LVDTs "The common solution is to use a capacitive bridge transducer, where a moving vane moves between two fixed plates that form a capacitive bridge that is unbalanced by the movement of the vane. With proper geometry, these can be very sensitive and linear over a range of several hundred microns. However, they are difficult to construct and have a working gap of less than a millimeter, and are prone to off axis sensitivity. They usually operate at relatively high frequencies, from khz to mhz, which complicates design and implementation problems" It looks like the AD device would solve some of these concerns. He then goes on to describe the VRDT. I suppose for the VBB sensor this would greatly simplify the electronic design if one can deal with small sensor gaps. I'm not sure about the noise. Does the VBB measure displacements in the 1 nm range?   --- Just thinking out loud. I think it

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