What are you using as a load?
In that link it was a motor.
You should replace the motor with a 470R resistor and connect your dimmer through a resistor to a capacitor down to ground. Then connect that to the dimmer.
By the way does any one else not seem to be able to see the schematics on this web site, I'm using Fire Fox and they never show up.
I'm getting 6v-12v.
How are you measuring this?
You won't get an accurate reading on a voltmeter as it is PWM.