USB Rudder Position Sensor for Boat Auto Helm: Slide Potentiometer or Distance Sensor?

Hi All;
I need to build or purchase (pre-built preferred) a device that can measure the physical location of the rudder on my boat and make this information available via a USB connection on my laptop. The purpose here is to enhance a home built auto helm.
I can build the mechanics no problem but need assistance with the rest:
Option 1) Be able to measure distance (~1 foot hopefully with up to 1+ mm accuracy) via whatever means (laser? Transducer?) and translate the measurement into any digital form.
Option 2) I can set up a long slide POT (i.e. 100k Ohm) via mechanical means (less accurate but will do) and somehow translate this into a digital measurement read via USB
Any recommendations here? I’d like to keep my costs down if possible.  I’m hoping there is a pre-built simple solution such as the magnetometer I used for compass heading.
Any assistance is appreciated.
Thx!

Hi Chris-What controls the rudder?  If it's a servo, then the duty cycle of the signal driving the servo should tell you where the rudder is. I think I would try to avoid a slide pot.  You'll likely have trouble keeping the element from getting contaminated.  A 1 foot long slide pot is going to be very expensive anyway. How about a rotary pot with an arm attached to the shaft?  It's going to be hard to get 1mm resolution with one foot of travel.   An absolute encoder wold work too, but would be more complicated. Another option is a Time of Flight Sensor.  I don't think you could get 1mm of accuracy, but you wouldn't miss by much.-Rick

I think Rick's on the money - use a rotary potentiometer (variable resistor) coupled directly to your shaft if you can't get the information directly from your control system. Using a linear pot you will need a mechanical coupling, it will likely have backlash... stay away from that can of worms.As for getting it to USB - there are any number of data acquisition products that will do the job for you, I'd use my National Instruments MyDAQ and Labview since (a) I already have them and (b) labview can do some processing and store data values and / or make graphs or real time displays.  But there are many more ways to skin this cat.

I must admit that I would be hesitant to use a potentiometer in a marine environment. I think it may become noisy over time, along with the backlash issue. I suggest you google “angular position sensor”. There are optical and magnetic offerings like this magnetic one. Because of the humidity/condensation I would also think twice about an optical sensor.

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