I'd be sceptical that an ultrasonic system would work, especially in the vicinity of the weldng/cutting process. Welding, cutting etc apparently produces a lot of sonic (and probably ultrasonic harmonics) "noise". Evidenced by the fact that hearing protection is recommended / required for welders. Never would have thought so, but apparently true.

I guess it really doesn't matter what you decide to use as long as you standardize on the voltage levels the software expects to receive. Output level shifting would be simple enough to implement for whatever sensor you choose.

Sage

no not had any issues over it catching as you say , however the hoop (4mm dia ) around the nozzle is slightly bow shaped to help in that case and the hoop is spring loaded with a light weight spring just enough to keep the LVDT touching at the rear ( mounted inside the tube mounting ) , i think you can see it but it may not be obvious , i have had thoughts of making it more of a bowl or dish shape

i'd certianly be game to look at capacitive sensors and see if we can come up with a better solution

works fine on my 600w CO2 Laser i dont get any interference pickup etc 
 

fer_mayrl

Any progress on your end here?  You stated "I have been looking into linear pots and LVDTs, and plan to have mach red the analog voltage and control the position of the z axis".

That's the correct solution - or so it seems to me.

For our part, we are planning to use one of the PoKeys input units for the analogue in (they will handle up to 4 analogues).  That gives us a nice expansion of useable I/O, and allows the analogue inputs and ability to use encoders (for mapping as an example).

Hey Flipz,

Not really, im still in the designing stages of the machine, and was just investigating the way i could (in the future) implement this.

Long way ahead since i think i am starting with plasma, and then go with the waterjet which is for what i need it.

Regards
Fernando

Fernando,
Would really like to know how this project is going ??
Dave

I strayed from that proyect... and I have not implemented it yet.
It will be a while...
Regards
Fernando