use diode as temperature sensor
HEllo all.
I think you cannot use a single diode to measure a certain temperature.
You need 2 diodes, one will be used as a reference.
Let's supose that you have both diodes fed by identical current sources I0.
One of the diodes, D1, is the measuring device and is in physical contact with the body you want to measure the temperature. The other diode, D2, the reference is inside of a box (electronic termometer that you are building) measuring the ambient temperature.
Vd1=Vt1 * ln (I0/Is1)
Vd2=Vt2 * ln (I0/Is2)
Is1=Is2 if the diodes are identical.
So,
Vd1*q/(K * T1) = Vd2*q/(K*T2) , T2= ambient temperature, T1= temperature to measure.
Then we find easily the temperature T1
T1= (T2/Vd2)*Vd1
You just need to measure Vd1 and you have T1. Since T2/Vd2 is constant and can be measured only once during the calibration.......2 diodes in the same temperaute, etc...
I hope it can help.
greetings to all
S.
PS: The diodes can also be replaced by bipolar transistors with metalic case like 2N2222.