NTC
NTC THERMISTOR
NTC
NTC THERMISTOR
OUTLINE
2
1200
4
This is a Negative Temperature Coefficient Resistor Whose
resistance changes with ambient temperature changes.
Thermistor comprises 2or 4 kinds of metal oxides of iron,
nickel,cobalt, manganese and copper, being shaped and
Sintered at high temperature(1200 to 1500 )
1500
NTC
Rt
Critical Technical Parameters of NTC Thermistor
Rt---Resistance Value at Zero-power
It's a resistance which is got at a fixed temperature on a
basis of a testing power which causes resistance to Vary in a
range which can be ignored in relation to the total testing eror.
R
25
R25---Resistance Value at Rated Zero-power
The design resistance of the thermistor usually refers to the
resistance value got at Zero-power at 25 , which is usually
indicated on the thermistor.
B Value
B value stands for the thermal exponent at a negative
temperature coefficient. lt's defined as a ratio of the balance
between the natural logarithms of resistance values at zero-
power to the balance between the reciprocals of the two
temperatures.The formula is as below:
R
T1
( 1
/
T
1
R
T2
1 )
T T
R
=
1 2
ln
T1
T
2
R
T2
T
2
T
1
R
T1
( 1
/
R
T2
T
1
1 ) T
1
T
2
R
=
ln
T1
T
2
R
T2
T
2
T
1
25
B
B
B=ln
B=ln
R
T1
R
T2
T1
T2
B
25 ( 298.
( 323.15K )
,B
In this formula: R
T1
is the resistance at Zero-power when the
temperature is T
1
R
T2
is the resisrtance at Zero-power when the temperature is
T
2
Unless otherwise specified, B value is got by calculating
the Zero-power resistances at 25
working temperature.
Resistance-to-Temperature Coefficient at Zero-power
It refers to the ratio of changes of a thermistor. Resistance
value at Zero-powerwhen The temperature, to the resistance
value at Zero-power The formula is as below:
B
T
2
( 298.15K ) and50
( 323.15K ) . It's not a firm constant within the range of
15K )
50
T
T
=
1 DR
T
=
R
T
DT
T
=
1 DR
T
=
R
T
DT
B
T
2
T
T
T
(
B
K
)
R
T
-
T
B
In this formula, " " stands for the resistance-temperature
coefficient at Zero-power when the temperature is T:
R
T
stands for the resistance value at Zero-power when the
temperature is T
T stands for thetemperature(in K)
B stands for B value
149
max
Max. steady state current.
thermistor at 25
.
max.
.
The maximum allowable continuous current passing through
Dissipation Coefficient
It's the ratio of the changes with a thermistor dissipation power, in
a
,
=
P/ T
pre-set
ambient
temperature,
to the changes with the
=
P/ T
changes in
temperature. The formula is as below:
response when the ambient temperature changes, within the
ranges of the working temperature.
Thermal Time Constant
At Zero-power and when amutatio occurs with the temperature,
the time "t", which is-spent for finishing 63.2% of the gap between
63.2%
C
=C /
the beginning temperature and the ending temperature in the
thermistor. is directly proportional to"c",the heat capacity of the
thermistor, and is inversely proportional to
constant. That is "
, the dissip ation
=C/
".
APPLICATIONS
UPS
Conversion power supply, switch power, UPS power, Kinds of electric
heter, electronic energy-saving lamps, electronic ballast etc all kinds
of power cicuit proterction of electronic equipments, filament proterction
of CRT, bulb and other lighting lamps.
150
NTC
NTC THERMISTOR
(NTC)
Surge-Arrestor NTC Thermistor
FEATURES
Small in size,high-powered, and very capable of bringing
down the surge current;
Quick in reaction;
High in B value and low in residual current;
Long service life and high reliability;
High coefficient of safety and wide range of application.
B
HOW TO ORDER
NTC
10
D-13
10
Negative Temperature Cofficient Resistor
Resistance Value:10
13
Diameter of Chip:
13
DIMENSIONS (mm)
A
D
F
C
E
(mm)
Type
D-20
D-15
D-13
D-11
D-9
D-7
A
MAX
C
1
D
MAX
E 0.05
1.0
1.0
0.8
0.8
0.8
0.5
F
MAX
4
4
4
4
4
4
22
16.5
14.5
12.5
10.5
8.5
7.5/10
7.5
7.5
7.5
7.5
5.0
7
6
6
5
5
5
13
2A
E
0.6
Remarks: " E"value may be 0.6 for resistors for which the chip's diameter is 13
and the working current is 2A.
151
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