SaM - Self-Heating

Remeber:

• Using a Common Thermal Lumped Parameter System:
  
  Where the Thermal Capacitance of the sensor is much smaller than that of the body of which we want to measure the temperature $T_X$, this is consider to have a simpler system.
  • NOTE: ${\dot{Q}}_S$ is a current generator.
    ${\dot{Q}}_S$ is the heat flux or flow quantity for the thermal lumped parameter systems, its units of measure is $\left[W\right]$.
• The temperature of the sensor $T_S$ is what we measure, we want $T_S$ to be as much closer to $T_X$ as possible.
• We consider to measure the temperature of the sensor at regime ($T_{S\infty }$), so when the transient has subsided.
• As a matter of fact if we perform the calculation we obtain that:$T_{S\infty }=T_X+R_{XS}{\dot{Q}}_S$Where:
  • We can see $R_{XS}{\dot{Q}}_S$ as the difference $\Delta T$ or measurement error.

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• We also need to say that, the difference between the real and measured temperature:$\Delta T=R_{XS}{\dot{Q}}_S$Depends on:
  • $R_{XS}$ the Thermal Resistance due to heat convection or conduction, which depends on the motion of matter, and material type both of the sensor and the target, and other properties.
  • ==While more importantly ${\dot{Q}}_S$ depends on the voltage ($V$) and current ($I$) feeding into the sensor, from this factor we have the problem of self-heating, since a higher current or voltage will increase ${\dot{Q}}_S$, so it will increase the difference $\Delta T$==.
• We have also seen how to reduce the effect of self-heating.

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Memory Card

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