I have a quick question to ask. I have an Arduino Uno reading 4 temperature sensors (LM35) in 4 different rooms. What happens is that the two nearest rooms give stable values, while the two further ones give very unstable measurements (the temperature keeps floating +-30C around the real values.)
I have connected all the sensors with Ethernet cables with the longest one being about 8-10m.
Is this problem due to noise picked up along the line? There are no strong electromagnetic sources along the way. I have also measured the voltage values on Arduino end with a multimeter: the values are all stable (and correct) and do not reflect the behaviour detected by Arduino.
Also, I have tried to substitute the LM35 in the farthest room with a photoresistor (the one in the starter kit) and this time the values read by Arduino are perfectly stable. I know that the LM35 works because I have tested it on a breadboard.
Can someone give my some help? Any idea is greatly appreciated.
Edit: I am adding a sketch, although it is a very basic setup: The only difference with the real layout is that there is also a Ethernet shield.