This is probably a NAMUR proximity sensor with variable resistance output. = With = only two wires and an appropriate interface circuit you can detect the gear = tooth, short circuit, open circuit and possibly reverse polarity. They are often used in hazardous areas (Ex, intrinsically safe applications= ). They can be either capacitive or inductive. The capacitive type has an inve= rsed = output characteristic compared to the inductive type. However, they are normally operated at a voltage between 8-15V. Some links: /Ruben > On Thu, 10 Sep 2009 13:53:12 +1200, Jinx wrote: > = > >> If the sensor only has two wires how can it have a 24VDC supply > >> *and* somewhere to see a resulting waveform? = > > > >It's quite common to superimpose information on the supply > = > I am quite familiar with 4 to 20mA current loop sensors and 2 wire Namur > type proximity switches and kludgy Dallas type '1' wire interfaces. = > = > The OP didn't mention anything about measuring his resultant waveform > across a load resistor. It sounded like he has one wire connected to +24v > and he scoped the other which plainly isn't powering the sensor if it is a > type that needs power. If it is a passive magnetic pickup sensor then why > would you connect one side of it to a +24v supply to start with? = > = > The OP has not provided enough information to allow anyone to do more than > make guesses at what he has and what he needs. > = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D Ruben J=F6nsson AB Liros Electronic Box 9124, 200 39 Malm=F6, Sweden TEL INT +46 40142078 FAX INT +46 40947388 ruben@pp.sbbs.se =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist