Remote Sensors and protocols

[javi.ar]

Hi, I want to connect remote temp & humidity sensors array(20 mts away) what would be the most easy protocol to implement ? should be wired type.
I have been doing some research, and I noticed that commercial units use RS485 as optional not the main option. Which I initially supposed to be the best option.
Any suggestion? thanks

[Ttelmah]

RS485, is not a protocol.

RS485, is a signaling standard. There are dozens (hundreds...) of 'protocols' used over this.

You need to consider:

1) RS485 to give it's proper noise performance, and signaling performance, requires wires with the right characteristic impedance and termination. Are you happy to do this?.
2) How noisy is the environment (electrical noise).
3) How are the systems powered.
4) Nature of the environment (industrial/home etc.), and the 'intention'.

If (for instance), there are nasty noisy devices nearby, then the protocol needs to have error handling and recovery.

If the systems are mains powered, and (for instance) the plugs might be in different buildings, you may need to consider the safety implications of cross phase power, or lightning strikes.

How fast data needs to be sent.
Simple RS232, is perfectly capable of sending signals this sort of distance at lower data rates.

Regulations on industrial sites would not allow many perfectly acceptable 'home' solutions. Solutions that are entirely adequate for your own use, may well not meet regulations if you go to sale.

Most industrial units will offer many different signaling standards and protocols. Often their own proprietary standards with perhaps Profibus over RS485 as a more expensive option. Simpler units may just use a proprietary protocol over RS232 as a cheaper short range option.