Advice on how I can achieve this?

I intend to make a sensor to detect how fast a turntable is spinning and in which direction.

I think what I want is two outputs, one for backwards and one for forwards, and their voltage should vary depending on how fast it is spinning in that direction.

Anybody know how I can achieve this?

Thanks, Ben

Try googling for 'quadrature detector' - and think non-optical mouse!.

I would use an optical sensor. Place a card on the turntable that has white and black segments printed on it. The sensor will output a frequency that is a function of the turntable speed and the number of white segments.

You would need to illuminate with a DC light, eg a LED, not by an AC light.

For the direction, I would print a long black segment followed by a short black segment spaced a couple of degrees apart with a second sensor viewing them. The direction of rotation can be determined by whether the short or long pulse comes first.