NTC Thermistors Glossary and Definition Negative Temperature Coefficient (NTC) thermistor are thermally sensitive semiconductor resistors, which show a decrease in resistance with temperature increases. NTC thermistors are made of polycrystalline mixed oxide ceramics. Making use of Negative Temperature Coefficient characteristics, NTC thermistor and temperature probe can be applied in temperature compensation, inrush current limit, temperature measurement and control, etc.
NTC Thermistor Rt --- Zero Power Resistance Value
The resistance value measured at a fixed temperature by adopting sufficiently low power consumption.
NTC Thermistor R25 --- Rated Zero-power Resistance Value
NTC Thermistor resistance value measured at 25oC by adopting sufficiently low power consumption.
NTC Thermistor Beta Value
NTC Thermistor Beta value is determined by the ceramic material and represents the slope of the R/T curve, expressed in the following formula
| In this formula: |
Rt1 is the Zero-power resistance at temperature T1; |
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RT2 is the Zero-power resistance at temperature T2. |
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Unless otherwise specified, B value is determined from measurements made at 25oC and 50oC It's not a firm constant within the range of working temperature. |
NTC Thermistor Zero-power Resistance-to-Temperature Coefficient
NTC Thermistor temperature coefficient of resistance is defined as the relative change in resistance referred to the change in temperature.
| In the formula: |
¦ÁT-zero power resistance-temperature coefficient at temperature T |
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RT- zero power resistance at temperature T |
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T-temperature (expressed in K) |
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B-B constant |
NTC Thermistor Dissipation Factor ¦Ä
NTC Thermistor dissipation factor ¦Ä is defined as the ratio of the change in power dissipation and the resultant change in the thermistor's body temperature. ¦Ä =¦¤P/¦¤T. ¦Ä changes in response when the ambient temperature changes, within the working temperature range.
NTC Thermistor Thermal Time Constant
NTC Thermistor Thermal Time Constant is the time required by a thermistor to change 63% of the difference between its initial and final temperature.
Thermal time constant can be a crucial parameter when selecting a temperature sensor to match an application.The thermal time costant (thermal respond time) of a temperature sensor is mainly influenced by:
Its design, e.g.sensor element, material used to assemble the sensor element in the sensor case, connection technolgy, housing.
Its mounting configuration, e.g. immersed, surface-mounted.
The environment it will be exposed to, e.g. air flow, inactive air, fluid.
NTC Thermistor Maximum Stable Current
Maximum successive current can be applied in NTC thermistor in the ambient temperature of 25oC
NTC Thermistor Resistance Temperature Characteristics
The dependence of the zero power resistance on its body temperature.
date: 2007-7-9
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