Hi Ron,
Perhaps more info was required on my part. As you say i want to measure between phases (AB, BC, CA). I have a daq card with 8 differential inputs. All i was asking was how should they be connected to meausre the voltage between the three phases.
It looks like i am going to have to connect the +ve of one channel to the -ve of another. As you also pointed out, it can go horibbly wrong if you connect it up the wrong way. I am so used to making single ended connections i am nervous about using differential.
The motor itself is just three coils of wire connected in star formation (stator) with a magnetic rotor down the middle. There are no drive electronics, its just a teaching aid motor.
Thanks