Hi Chris,

Thanks for your input.  Could you steer me to a web address where =
Coleman's design is described?  I have found his description for a very =
elegant looking horizontal sensor, also called the MKXV.  However, I've =
decided that my next project will be a vertical of some sort.  The =
electronics for the horizontal would certainly work.  If he has come up =
with a vertical design that is as solid looking as his horizontal one, =
I'd sure like to see it.

Larry
  ----- Original Message -----=20
  From: ChrisAtUpw@..........
  To: psn-l@.................
  Sent: Tuesday, December 17, 2002 4:20 PM
  Subject: Re: Vertical "SG" sensor?


  In a message dated 17/12/02, lconklin@............ writes:=20


    I've been thinking about building a vertical sensor.  One design =
I've been=20
    considering would use a bowed leaf spring similar to the Sean-Thomas =

    Morisssey design, combined with the differential capacitor sensor =
using=20
    Larry's SG electronics board.  I'd be interested in hearing whether =
anyone=20
    else has tried this or if anyone has any thoughts regarding the =
viability of=20
    this approach.


  Hi Larry,=20

        The SG oscillator / capacitor / tuned circuit design is quite =
temperature sensitive and the technique is 'out of date', by maybe =
twenty years. Allan Coleman has a good capacitor sensor design on his =
Website. There is also one capacitor bridge design in the Linear =
Technology archive notes dated early '96, "Bridge Measures Small =
Capacitance" by Jeff Witt. There are several subsequent designs for =
capacitance measurement, but they seem designed to actually measure =
capacity, rather than be useful as a differential movement sensor. (The =
capacity is inversely proportional to the separation of the plates, =
which is what you are interested in.) Alternatively, you could use a =
modified NE5521 LVDT circuit with a fet amplifier on the sense input. =
They work pretty well.=20
   =20
        Leaf springs tend to suffer from fewer resonance problems than =
coil springs. Again, why not have a look at Allan's design for a =
vertical? His MKXV vertical is a compact and most interesting design.=20

        Regards,=20

        Chris Chapman=20







Hi Chris,
 
Thanks for your input.  Could you steer me to a =
web=20
address where Coleman's design is described?  I have found his =
description=20
for a very elegant looking horizontal sensor, also called the =
MKXV. =20
However, I've decided that my next project will be a vertical of some=20
sort.  The electronics for the horizontal would certainly =
work.  If he=20
has come up with a vertical design that is as solid looking as his =
horizontal=20
one, I'd sure like to see it.
 
Larry

  
----- Original Message ----- 
  From:=20
  ChrisAtUpw@....... 
  
To: psn-l@.............. 
  
Sent: Tuesday, December 17, =
2002 4:20=20
  PM
  
Subject: Re: Vertical "SG" =
sensor?
  

In a =
message dated=20
  17/12/02, lconklin@............=20
  writes: 


  I've been thinking about building a vertical sensor. =
 One=20
    design I've been 
considering would use a bowed leaf spring =
similar to=20
    the Sean-Thomas 
Morisssey design, combined with the differential =

    capacitor sensor using 
Larry's SG electronics board.  I'd =
be=20
    interested in hearing whether anyone 
else has tried this or if =
anyone=20
    has any thoughts regarding the viability of 
this =
approach.

Hi Larry,=20
  

      The SG oscillator / =
capacitor /=20
  tuned circuit design is quite temperature sensitive and the technique =
is 'out=20
  of date', by maybe twenty years. Allan Coleman has a good capacitor =
sensor=20
  design on his Website. There is also one capacitor bridge design in =
the Linear=20
  Technology archive notes dated early '96, "Bridge Measures Small =
Capacitance"=20
  by Jeff Witt. There are several subsequent designs for capacitance=20
  measurement, but they seem designed to actually measure capacity, =
rather than=20
  be useful as a differential movement sensor. (The capacity is =
inversely=20
  proportional to the separation of the plates, which is what you are =
interested=20
  in.) Alternatively, you could use a modified NE5521 LVDT circuit with =
a fet=20
  amplifier on the sense input. They work pretty well. 
 =20
  
      Leaf springs tend to suffer =
from fewer=20
  resonance problems than coil springs. Again, why not have a look at =
Allan's=20
  design for a vertical? His MKXV vertical is a compact and most =
interesting=20
  design. 

      Regards,=20
  

      Chris Chapman=20