The final verdict
Guys et al,
Good news, all works fine, just wanted to share some measurements with you, and a few [minor] open ends.
Please have a look at first attachment. This really looks cool and OK.
The green-line is a temp.sensor without the RC-circuit, and the blue-line with the RC-circuit installed on the board.
At around 12:35 and at 13:00 I give the sensor a kick to see how it responds.
One strange thing, I'm not so bothered about, but I'm curious anyway: look how after the kick the temperature drops, raises again, drops, raises and undershoots to finally reach it's end-value. I should probably ask a thermodinamic expert, but does anyone have a clue to why this is?
If you look at the second file, that's where the sensor has a loose contact. Blue line starts at around 18 degrees, drops to 15. I start fidling a bit on the wires, correct value comes up, starts dropping again at around 11:15, I heat up the sensor, nothing happens, fidling with the wires and the correct value comes up again and starts dropping. Now I suspect that at the point where the value starts dropping in an almost liniar way, this is because the capacitor unload via the 10M resistance in the A/D-cicruit, correct? And the tiny spikes in the values are the result of the inaccuracy of the A/D-convertor [it's a 12-bits, from 0mV-4096mV obviously in steps of 1mV, with an accuracy of 2mV, I guess it's actual accuracy is therefore 11-bits, or looking at the graph perhaps even 10-bits].
If anyone can/want to do the math for the decharge of the cap.:
So at 10:20 temp is around 17.8 degrees celsius ~ 678 mV
So at 10:50 temp is around 16.0 degrees celsius ~ 660 mV
Not really needed, just curious if it figures...
Best regards,
Martin