Celsius zero shift for two -terminal temperature sensor circuit not completely understood?

Thread Starter

TarikElec

Joined Oct 17, 2019
125
Hi everyone,
So, as I am reading this part of amazing book, the Celsius zero shift for two -terminal temperature sensor circuit of Fig 21.19 is not fully understood by me.
what I understood:
-The \[ V_{\text{Temp}} \] at the two terminal of the Zenner diode is directly coming from the circuit Fig.21.18 which is the output is of value (10mV/K)*T
-the current frlowing through the V-(not in) is the sum of Vo/10Kohm+Vref/9.16Kohm.
-the only time I get the Vo=-2.73V is when the \[ V_{\text{Temp}}=0 \] and a that value the current flowing through the V-(not in) is negligible.
What I did not understand:
1-where did the formula come from, it is like converting Kelvin to Celsius? \[ V_{\text{o}}=\left(\frac{10\text{mV}}{\text{Celsius}}\right) v\]
2-what does the \[ v\] stand for?
3-at C=0, it means Tk=273Kelvin and then V_temp=10*273=2.73V which bring the Vo~=0V?

here , is the page of the book and falstad simulator:
1711553927254.png
1711554073583.png
 

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Thread Starter

TarikElec

Joined Oct 17, 2019
125
Do you know that degrees Celsius is just degrees Kelvin plus 273.15?
Zes I know that it is the other way around: Tk=Tc+273.15. but that does not answer my question of if the voltage across the zenner diode is the Vtemp of the fig 21.18 for example


I think I understood it. the circuit in Fig 21.19 is just the Tc=Tk-273 and the the -273uA flowing to the R=10Kohm of the Vo is just this reflection of 10Kohm*(-273K) at Tc=0(0=Tk-273K).
the 273uA comes from the Vref/9.16 Kohm that flows through the 10Kohm of Vo as Vtemp=0V at Tk=0 where no current flows via the 10Kohm connected to the zener diode
but at Tk=273,Tc=0, we have Vtemp=2.73V and this leads to Vo=0
 
Last edited:

Casperson

Joined Aug 11, 2021
4
Your temperature sensor is not a zener diode, it's an integrated circuit that is connected like a zener diode and has a voltage drop of 10 mV per K,

Note: K is only called Kelvin, not degree Kelvin, because it is an absolute temperature and not a relative temperature like degree Celsius, degree Fahrenheit or degree Réaumur (degree means relative scale).
 

Thread Starter

TarikElec

Joined Oct 17, 2019
125
Your temperature sensor is not a zener diode, it's an integrated circuit that is connected like a zener diode and has a voltage drop of 10 mV per K,

Note: K is only called Kelvin, not degree Kelvin, because it is an absolute temperature and not a relative temperature like degree Celsius, degree Fahrenheit or degree Réaumur (degree means relative scale).
Thanks, I never knew about the Kelvin as non degree
 
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