I plan to use this circuit to power a windwane's potentiometer which is around 10k:
As you see I want to set the excitation voltage for the vane pot to around 9 or 10V where the opamp will be supplied directly from a 12V switch mode power supply. For this purpose I will use an LM317 to obtain 9 or 10V for the vane excitation. So I will set LM317 for 9 or 10V DC. I will mount the vane in a box around 50m height which will stay there at least 3 months.
Since I will use a linear voltage regulator I decided to find out whether I need a heatsink.
I have encountered two challenges which I put here as questions:
1-) In the datasheet when I check the thermal resistances I cannot figure out which model I should use:
Mine is T0-220, but in the datasheet there is two types namely as KCT and KCS. But my model is "LM317T/NOPB". And on it it is written "LM317T +P". So should I use the thermal resistance for KCT or KCS?
2-) Here is how I calculate the ΔT:
ΔT = θJA * P
In my case:
P = V^2 / R = 10^2 / 10000 = 0.01W
But for junction to ambient temperature I used to use the following:
Junction to ambient = Junction to case + Case to Ambient
But in the datasheet there is no Case to Ambient but there is Junction to ambient. Does "junction to ambient" already include "case to ambient"? Should I in my case only use Junction to ambient? If so in my case ΔT becomes like 4°C, and I conclude I don't need heatsink. Do I calculate correct and does it matter the duration like three months when it comes to using heatsink?