In a message dated 2008/09/18, cjburch@........... writes:

> Does anyone have experience with Variable Reluctance Displacement 
> Transducers 
> (VRDTs)?  Morrissey appears to have used them extensively and they seem to 
> have a number of advantages.  They are inexpensive and easy to fabricate.  
> They are sensitive and have a low impedance output so parasitic capacitance 
> wouldn't be a problem.  
> 
> It's true that they do produce heat, of course.  Any other drawbacks?

Hi Chuck,

       They produce very little heat. Sean disasembled miniature audio 
transformers from Mouser and used the E cores and the ready wound formers. The range 
is only about +/-1mm.
       You need a sine wave drive, but this is not a problem.
       The one that I use has a resolution of <10 nano metres.

       Depends on what you want it to do, the range, the resolution, the 
frequency response and on what equipment.
       Variable reluctance, LVDTs, LCDTs, Silicon optical, Hall effect 
magnetic and coil + magnet sensors have all been used OK.

       Regards,

       Chris Chapman   
In a me=
ssage dated 2008/09/18, cjburch@........... writes:



Does anyone have experience wit=
h Variable Reluctance Displacement Transducers 

(VRDTs)?  Morrissey appears to have used them extensively and they seem=
 to have a number of advantages.  They are inexpensive and easy to fabr=
icate.  They are sensitive and have a low impedance output so parasitic=
 capacitance wouldn't be a problem.  



It's true that they do produce heat, of course.  Any other drawbacks?



Hi Chuck,



       They produce very little heat. Sean dis=
asembled miniature audio transformers from Mouser and used the E cores and t=
he ready wound formers. The range is only about +/-1mm.

       You need a sine wave drive, but this is=
 not a problem.

       The one that I use has a resolution of=20=
<10 nano metres.



       Depends on what you want it to do, the=20=
range, the resolution, the frequency response and on what equipment.

       Variable reluctance, LVDTs, LCDTs, Sili=
con optical, Hall effect magnetic and coil + magnet sensors have all been us=
ed OK.



       Regards,



       Chris Chapman