Views: 0 Author: Site Editor Publish Time: 2022-01-27 Origin: Site
Thermistors are constantly being upgraded to meet the needs of different electronic machines. The development of epoxy thermistor meets the requirements of equipment with high-temperature requirements. It is more sensitive to temperature detection, which improves the efficiency of the equipment.
What are the factors that affect the conductivity of epoxy thermistors?
What are the functions of an epoxy thermistor?
What is the resistance temperature characteristic of epoxy thermistor?
(1) Temperature: Conductivity has a great correlation with temperature. The conductivity of metals decreases with increasing temperature. The conductivity of semiconductors increases with increasing temperature. Within a certain temperature range, the conductivity can be approximated as being proportional to the temperature. To compare the conductivity of substances at different temperature conditions, a common reference temperature must be set. The correlation between conductivity and temperature can often be expressed as the slope of a graph of conductivity versus upper temperature.
(2) Doping degree: The doping degree of solid-state semiconductors will cause great changes in electrical conductivity. Increasing the degree of doping will result in high conductivity. The conductivity of the aqueous solution depends on the concentration of the solute salt in it or other chemical impurities that will decompose into the electrolyte. The conductivity of a water sample is an important indicator for measuring the salt, ion, and impurity components of water. The purer the water, the lower the conductivity (the higher the resistivity). The conductivity of water is often recorded as the conductivity coefficient; the conductivity coefficient is the conductivity of water at a temperature of 25°C.
(3) Anisotropy: Some substances have anisotropic conductivity, which must be expressed in a 3 X 3 matrix (using mathematical terms, the second-order tensor, usually symmetric).
Epoxy thermistors can also be used as electronic circuit components for instrument circuit temperature compensation and thermocouple cold junction temperature compensation, etc. Using its self-heating characteristics can realize automatic gain control, forming an RC oscillator amplitude stabilization circuit, delay circuit, and protection circuit. When the self-heating temperature is much higher than the ambient temperature, the resistance value is also related to the heat dissipation conditions of the environment. Therefore, the thermistor is often used in flow meters, flow meters, gas analyzers, and thermal conductivity analysis to make special detection elements. Epoxy thermistors are mainly used for overheating protection of electrical equipment, non-contact relays, constant temperature, automatic gain control, motor startup, time delay, color TV automatic degaussing, fire alarm, and temperature compensation.
R=R0exp(B(1/T-1/T0)): R: resistance value at temperature T(K), Ro: resistance value at temperature T0, (K), B: B value, *T(K )=t(ºC)+273.15. The B value of epoxy thermistor is not constant, and its change varies depending on the material composition, up to 5K/°C. Therefore, when formula 1 is applied in a larger temperature range, there will be a certain error between the measured value and the actual value. Here, if the value of B in Equation 1 is calculated as a function of temperature shown in Equation 2, the error from the actual measured value can be reduced, and it can be considered to be approximately equal.
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