SaM - Definition of Thermistor

Remeber:

Thermistor are made of a thick layer of ceramic (semiconductor). They are very used, and cost less than RTDs:
In a thermistor we exploit the semi-conductive behavior of the ceramic material which gives us a thermally activated conductivity.

Thermistor have a Negative Temperature Coefficient (NTC or Negative TCR), which remember is defined as:$\alpha =\frac{dR}{dT}\cdot \frac{1}{R}$Also the formula that governs thermistor is non-linear:$R(T)=R_A\cdot e^{\beta \left(\frac{1}{T}-\frac{1}{T_A}\right)}$Where:

• $R_A$ : $R(T=T_A)$
• $\beta \in \left[3000°\text{K}÷5000°\text{K}\right]$
• $T_A$ : ambience temperature $\left(T_A=300°\text{K}\right)$

We have also seen how we can describe the equation of a thermistor with the Steinhart-Hart Relashionship.

• They are of about $100\mu \text{m}$ in lenght.
• The temperature range is between $\left[-50°\text{C}÷150°\text{C}\right]$.IMPORTANTE
• Some common values for the thermistor resistance are in the order of $\left[1.8\text{k}\text{ohm}÷10\text{k}\text{ohm}\right]$.IMPORTANTE
• Thermistor are made of a thick layer of Ceramic (semiconductor).
• They are commonly used, and ==cost less than RTDs==.
• For this material here we have we exploit the semi-conductive behavior of this material which gives us a thermally activated conduction.
• We expect resistances which decreases with temperature, because the higher is the temperature the larger is the number of carriers that becomes available or that can overcome a barrier in any case.
  Something operating in the freeze out or in the intrinsic, the carriers has to be freed by the temperature, so there is a conduction which is related with an exponential function with temperature.

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Memory Card

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• Thermistor are made of a thick layer of Ceramic (semiconductor).
• They are very used, and cost less than RTD.
• For this material here we have we exploit the semi-conductive behavior of this material which gives us a thermally activated conduction.
• Something operating in the freeze out or in the intrinsic, the carriers has to be freed by the temperature, so there is a conduction which is related with an exponential function with temperature.
• And obviously we expect resistances which decreases with temperature, because the higher is the temperature the larger is the number of carriers that becomes available or that can overcome a barrier in any case.

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