Max wire length for ultrasonic range finder

i have two big water tanks that i would like to setup a water level meter for each tank is about 35-40 ft. away from where i would like the LCD to display the water levels and each tank is in the opposite direction. after much reading, it seems an Ultrasonic sensor would be work well with my application. Wireless is not an option as this is in a heavy rebar concrete building with many walls/floors in between, and i have no power source at the water tanks. I'm hoping to do this with one arduino and two sensors using cat 5 cables or anything similar.

my other option is to use 2 arduinos at the water tank locations which i am trying to avoid due to my budget.


Two things I know of could be a problem.

The wire resistance and noise.

You can calculate the voltage drop by knowing you wire resistance per ft

According to wikipedia this is 0.188 ohm/m for a standard cat 5 cable. You have ~12m which gives 2.2ohm. So it's like having a resistor with 2.2 ohm instead of your cable.

As for noise you could look into differential signaling.

But I doubt that will be necessary.

Hi, Take a look at this:

This is an ultrasonic sensor that can be used remotely with serial data. CAT5 cable would be good. A twisted pair for each of: - Data in - Data out - +5 and Ground.

DISCLAIMER: Mentioned stuff from my own shop...

You don't need two full arduino boards, two barebones atmega328p work just as well if your up for a little soldering on a perfboard Dependingg on the noise of the enviroment regular ttl serial should work If not rs485/232 will definetly work