Posted 15 February 2011 - 04:59 AM
I am able to reproduce a similar situation to what Marius has encountered, the LM35 reading jumps around inconsistently for me from the analog input pin. When I put a voltmeter on the wire (while everything is still connected as is on the board, bridging voltmeter terminals from A5 to netduino ground - same as sensor ground) it is a very steady 196 mV, which is exactly as expected. During the constant 19.6 mV from the voltmeter, the netduino is jumping significantly, +/- 150% of the 196 mV reading.
Here's the crazy part, when I disconnect my laptop from wall power, and run off batteries, the analog input pin falls exactly in line with the reading I get directly off the sensor. Plug the laptop back in and the analog input goes haywire again. I can reproduce at will by cycling the switch on my surge protector.
Any ideas what would cause this or how to remedy it?