Lm35 and low pass filter

Hello all. I've seen this discussed a few times, but I have a specific question. I have a LM35 soldered to about 4 feet of cat6. Gnd and +5 are a twisted pair and about is on its own. I wAs getting a lot of noise. I added a 1k resistor to about and a 10uF cap from Vout to Gnd. I am stable to about .5 degree now. Anyone see any issues with my configuration. Specific don't want to fry he sensor to arduino.


That 10uF might leak and influence the analog value. 4 feet is only 1.2 meters. That is a short wire. Only 1.2 meters should not give so much noise. Not even 0.5 degrees of noise. What else is there on the cable ?

Have a look at the datasheet, page 9, figure 14. http://www.ti.com/lit/ds/symlink/lm35.pdf It seems that it can only drive a capacitive load of 50pF. So you have to do something like in figure 14 or 15.

You should also average a few samples in your sketch. Start with the average of 5 samples. That should already improve it a lot.

Thanks for the info. With 4 feet I was getting 10 degree swings. Worked perfect with short leads, but the Cat6 was noisy. I'll try a 1uF cap as recommended. Amazing how much the analog picks up on a wire