Check the post below "RPM via RF"

A low power radio transmitter might do the trick.

How critcal is the pressure signal you are measuring? A filtering circuit may take out some of the slip ring noise.

Insulating the slip rings and grounding the shaft, via an uninsulated slip ring, or strap arrangement may also help.

Good luck, Dan76

hi,
   Your are looking at installing a pt on the rotating device and using the slipring to
 a) power the device and
 b) transmit the signal.

If you are taliking about a standard sort of industrial 4- 20mA tx with a supply in the order of 24v dc then you must have really shitty slip rings.
How fat is the device turning?

I would imagine the tx would handle the noise of the slip ring. I have used them on slow turnig filter press type appllications with out too much grief. The impedance of those types of devices is relatively low. Typically feeding into a 250 ohm resistor at the PIC or PIA.

If you have a power supply on board the rotating device have a talk to some of the bigger name controls companies - eg Omron, black box Erwin Sick for wireless data systems that would kill the problem no sweat.
let us know how it goes
Don

I once designed a dip-time sensor which ran around on a "solder dial" which dipped electronic parts in a solder wave to tin the part leads. I used a gel-cell to power the sensor, and an infra-red LED to transmit the sensor data to a phototransistor, the combination housed in a small co-axial pair of opaque plastic pipes mounted across the center of rotation. The phototransistor signal then went to the display unit on the machine console to allow the operator to adjust the speed to put dip time precisely at spec.

This LED/phototransistor "optical slipring" worked great in this exceptionally hot, greasy, dirty and electrically noisy environment. Once every couple of months the gel-cell had to be recharged overnight. Although the energy use was low enough that a solarcell could have been used to charge the battery from factory lights, the peanut oil evaporating off the solder into the air would quicky cloud the cell in this application.

Kevin VanZuilen "KevinVZ"

Suggestion: What about a sound (or an ultrasound) waves transmission from the rotating shaft pressure transducer?

You may consider using a rotating transformer. It is basically two ferrit "E"-cores with a small airgap between them, one of them rotates the other is fix. You can power the circuit by it, too.
There are double "E" cores, too with |__|__##0##__|__|
cross-section ("O" is the hole in the center ) which
has two concentric channels.

Want a sketch? Send fax# <nbucska@pcperipherals.com>>
 Nick