I2c and RS485 at Same Time

I was asked to build a complicated (for my beginner level) sensor network across a large area (a few hundred meters). The area can be broken down into four major groups based on location. Within these groups, the sensors are still located up to a few hundred feet apart.

Because the sensor wires will be long, i would like to use 4 to 20mA sensors. I will connect these sensors back to the Arduino using a special connector -

There will be up to eight (8) 4 to 20mA sensors (measuring water tank levels) on each arduino.

The Arduinos will all need to talk to a master ardunio that i will keep connected to a computer and make a graphical user interface using other software with input from the sensor data.

Can i use RS485 with Mudubus for the link between the Arduinos? Will the RS485 interfere with the use of the i2c on the arduino?

Any recommendations?

Since they are tank level sensors, i want to continuously monitor the sensors (lets say at a minimum of every 10 seconds).

Do you want to make Arduino communication using Serial or some soft serial? Software Serial can cause or have problems when used in parallel with other communication channels.

DrDiettrich:
Do you want to make Arduino communication using Serial or some soft serial? Software Serial can cause or have problems when used in parallel with other communication channels.

I do not know what is better.

If i switch to Arduino Due would that help? I see it has multiple tx/rx pins?

what interfaces do the senors have (as this limits the communication options) or does each sensor have its own microcontroller?

RS485 is a multidop system so you can have multiple sensors - however, you would require some protocol and addressing system to identify each sensor

you mention a master Arduino connected to a computer for display - why not connect the RS485 directly to the computer?

For debugging purposes an Arduino Mega also is an option, it has 4 Serial channels. If no serial debug output is required, any of the small Arduinos is sufficient later.

horace:
what interfaces do the senors have (as this limits the communication options) or does each sensor have its own microcontroller?

The sensors have analog outputs of 4 to 20 mA (industry standard), nothing digital. The shield handles these inputs and has an I2C interface.

there a number of analogue to RS485 data acquisition systems (including modbus) - try a web seach for analogue to rs485