From: "Larry Conklin" lconklin@............

Date: Wed, 18 Dec 2002 22:03:21 -0500

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Larry,=20 The SG oscillator / capacitor / tuned circuit design is quite = temperature sensitive and the technique is 'out of date', by maybe = twenty years.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=20Hi 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@.......Sent:Tuesday, December 17, = 2002 4:20=20 PMSubject: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