I want to build a centralized system which will be getting values from many sensors around an agricultural field.
The field's large area leads to long wires going from sensors to the central controller. I do not wish to use repeaters in between. How far (in metres) can those typical 5 V cheap sensors (specifically PIR sensor) transmit without the output fading too much?
I understand that this distance of signal travel depends on current delivering ability of the sensor and also on the resistance of the transmission wire. So say if I use a high impedance op-amp at the input, hence solving the current problem, how far would I be able to sense the signal from sensors considering that much electromagnetic interference is not around?