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N_09L00331 Datasheet(PDF) 3 Page - AVX Corporation
AVX [AVX Corporation]
1 – INTRODUCTION
NTC thermistors are thermally sensitive resistors made from
a mixture of Mn, Ni, Co, Cu, Fe oxides. Sintered ceramic
bodies of various sizes can be obtained. Strict conditions
of mixing, pressing, sintering and metallization ensure an
excellent batch-to-batch product characteristics.
This semi-conducting material reacts as an NTC resistor,
whose resistance decreases with increasing temperature.
This Negative Temperature Coefficient effect can result from
an external change of the ambient temperature or an inter-
nal heating due to the Joule effect of a current flowing
through the thermistor.
By varying the composition and the size of the thermistors,
a wide range of resistance values (0.1Ω to 1MΩ) and tem-
perature coefficients (-2 to -6% per °C) can be achieved.
RoHS (Restriction of Hazardous Substances - European
Union directive 2002/95/EC).
ELV (End of Life-Vehicle - European Union directive
All Thermistor Products have been fully RoHS/ELV since
Chip Thermistor NB RoHS/ELV Status: external Plating
100% smooth semi-bright Sn as standard SnPb Termination
available on request.
2 – MAIN CHARACTERISTICS
2.1 CHARACTERISTICS WITH NO DISSIPATION
2.1.1. Nominal Resistance (Rn)
The nominal resistance of an NTC thermistor is generally
given at 25°C. It has to be measured at near zero power
so that the resultant heating only produces a negligible
The following table gives the maximum advised measure-
ment voltage as a function of resistance values and thermal
This voltage is such that the heating effect generated by the
measurement current only causes a resistance change of
2.1.2. Temperature -
Resistance characteristics R (T)
This is the relation between the zero power resistance and
the temperature. It can be determined by experimental mea-
surements and may be described by the ratios R (T) /R
is the resistance at any temperature T
R (25°C) is the resistance at 25°C.
These ratios are displayed on pages 29 to 33.
2.1.3. Temperature coefficient (
The temperature coefficient ( ) which is the slope of the
curve at a given point is defined by:
and expressed in % per °C.
2.1.4. Sensitivity index (B)
The equation R = A exp (B/T) may be used as a rough
approximation of the characteristic R (T).
B is called the sensitivity index or constant of the material
To calculate the B value, it is necessary to know the resis-
of the thermistor at the temperatures
The equation: R
B (K) =
Conventionally, B will be most often calculated for tempe-
= 25°C and T
= 85°C (298.16 K and 358.16 K).
In fact, as the equation R = A exp (B/T) is an approximation,
the value of B depends on the temperatures T
which it is calculated.
For example, from the R (T) characteristic of material M
(values given on page 29), it can be calculated:
B (25 – 85) = 3950
B (0 – 60)
B (50 – 110) = 3983
When using the equation R = A exp (B/T) for this material,
the error can vary by as much as 9% at 25°C, 0.6% at 55°C
and 1.6% at 125°C.
Using the same equation, it is possible to relate the values of
the index B and the coefficient
• A exp (B/T) •
expressed in %/°C
Maximum measuring voltage
δ = 2 mW/°C δ = 5 mW/°C δ = 10 mW/°C δ = 20 mW/°C
10 < R 100
100 < R 1,000
1,000 < R 10,000
10,000 < R 100,000
R < 100,000
1 - 1
1 - 1
A exp (B/T)
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