'POT' issues with long cable

[ardhuru]

Hi Adhuru,
Curiosity has got me, what are you trying to keep track of the water level in ? Have you considered using a float and some switching method like hall effect or optical ?

Basically 3 tanks 2K to 5K litre capacity, non-metallic, heights 6 to 8 feet. Having got a quantitative reading from all 3 tanks, there's logic that also controls a pump to keep the levels at a required level.

Unfortunately, yes, I did look at the alternatives you mention and had to discard them for various reasons:

Floats (I assume you mean the kind that is anchored, and has a float connected to a pot): would be difficult to get movement thruought the height of the tank. Also, the ambient humidity would junk it in a short time.

Hall effect or optical would be good, but I need to sense 10 levels in each tank; would be complex/expensive. I even considered an IR scheme with the technique Bruce describes on his site for distance measurement. Not to mention optical encoders with a float.

Is there power available in the area where the sensor goes? Is radio telemetry an option?

Yes, power is available, but I think if i could get away with data-over-the-Vcc-line, that would be more elegant. And cheaper than RF.

But first, I'm going to try out Melanie's suggestion about PWM and ADC;

This thread has many useful possibilities for people around the globe, and I am betting many are interested. So I just HAVE to say . . . GOOD SUBJECT !

Thanks; I've been trying to achieve this for a long time. If there's any interest on this subject, I'll keep posting my observations on this thread.