[Lloyd Burns]

It matters little what language you use, but measuring voltages is something to do in hardware.

As I see it, your biggest problem is a voltage that goes minus. If you know how, or know someone who knows how, to make an op-amp take the voltage and make it 0-5 V (ie +2.5 V +/- 2.5 V), you could use a Basic Stamp and an ADC0831 A to D Converter. National Semiconductor used to make this little wonder, and Yahoo ought to get the data sheet for you. (The complete sheet is 550K on my HD.) Read it to find out about successive approximation ADC.

Many processors have a pin or 2 to some power of analog (ADC) input, and are very quick at the approximations, sometimes doing it in the background, with no help from your program.

I have to wonder what you are using to sense distance - I programmed a PIC 12C508 to drive a 40 kz (ultrasound) transducer, and give me the distace in mm, from 15 cm out to 1 m, resolving 1 mm quite accurately, and I got a machine-readable output. It would easily read out to 3 m, but that is a matter of waiting. I had to tweak the processor speed just a fraction to get mm counts.

If you would like to discuss ADC or distance measurement further, I'm reachable.