18/11/2013
Disc & Chip Thermistors
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Disc & Chip Thermistors
Temperature Measurement and
Control Devices
DISC and CHIP
Style
NTC Thermistors
DISC & CHIP
STYLE
Features
Wide Ohmic
Value Range
Accurate &
Stable
Fast Thermal
Response Time
Tight Tolerances
High Sensitivity
Negative Temperature Coefficient (NTC) thermistors are thermally sensitive
semiconductor resistors which exhibit a decrease in resistance as absolute
temperature increases. Change in the resistance of NTC thermistor can be brought
about either by a change in the ambient temperature or internally by self-heating
resulting from current flowing through the device. Most of the practical applications of
NTC thermistors are based on these material characteristics.
NTC DISC & CHIP Style Devices
RTI manufactures
DISC & CHIP
style thermistors in resistance values ranging from 1.0
ohm to 500,000 ohms. These devices are suitable for a range of resistance values
and temperature coefficients from relatively low resistance and temperature
coefficients to very high values. Precision resistance tolerances are available to 1%.
Standard resistance tolerances are from 5% to 20%. All tolerances are specified at
25°C or may be specified at any temperature within the operating temperature range
of the thermistor.
Thermistor Terminology for Temperature Measurement & Control
Devices
D.C. - The dissipation constant is the ratio, normally expressed in milliw atts per degree C
(mw /°C), at a specified ambient temperature, of a change in pow er dissipated in a
thermistor to the resultant change in body temperature.
T.C. - The thermal time constant is the time required for a thermistor to change 63.2% of
the total difference betw een its initial and final body temperature w hen subjected to a
step function change in temperature under zero-pow er conditions and is normally
expressed in seconds (S).
Alpha ( ) or Tem perature Coefficient or Resistance - The temperature coefficient
of resistance is the ratio at a specified temperature, T, of the rate of change of zero-
pow er resistance w ith temperature to the zero-pow er resistance of the thermistor. The
temperature coefficient is commonly expressed in percent per degree C (%/°C).
Applications
NTC
DISC & CHIP
Selection
Considerations
Select Req'd.
Resistance
Value &
Temperature
Coefficient
Determine
Accuracy
Req'd.
Review Pow er
Dissipation
www.rtie.com/category-s/91.htm
Time and temperature are two of the most frequently measured variables. There are
numerous ways of the measuring temperature electronically, most commonly by
thermocouples and negative temperature coefficient (NTC) thermistors. For general
purpose temperature measurement, NTC temperature sensors can operate over a
wide temperature range (-55 to +300°C). They are stable throughout a long lifetime,
and are small and comparatively inexpensive. Typically, they have negative
temperature coefficients between -3.3 and -4.9%/°C at 25°C. This is more than ten
(10) times the sensitivity of a platinum resistance thermometer of the same nominal
resistance. RTI's
DISC & CHIP
style thermistors are used in many applications that
require a high degree of accuracy and reliability.
Some of the most popular applications of NTC thermistors include:
Temperature Compensation
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18/11/2013
Dissipation
Determine
Operating
Temperature
Range
Review Thermal
Time Constant
Disc & Chip Thermistors
Temperature Compensation
Temperature Measurement & Control
Fan Motor Control
Fluid Level & Temperature Sensors
Selection considerations for NTC
DISC & CHIP
Devices
Power dissipation is a common problem in the use of thermistors as they can only
dissipate a certain amount of power. If the power dissipated exceeds the dissipation
constant (D.C.) rating of the sensor it is likely that it will exhibit self heating. Most
thermistors dissipate from 1 to 25 mW/°C nominal. This means that the resistance
changes by an equivalent of 1°C for each D.C. rating (mW/°C) for the selected
device. To maintain a higher degree of accuracy, temperature error caused by self-
heating should be an order of magnitude less than the required sensor accuracy. For
many applications, this degree of accuracy is not required and a less stringent de-
rating may be adequate. Several options to reduce the thermistor power are to
increase the thermistor resistance, lower the source voltage and/or increase the
series resistor in the divider circuit.
As an example, if the D.C. of the thermistor selected is 5 mW/°C and the power
dissipated by the device is 20 mW/°C, then a 4°C error is induced due to the effect of
self-heating. To minimize this effect, a factor can be derived simply by taking the DC
rating times 10
-1
(one order of magnitude lower) and use it in the power equation to
produce a good approximation of the maximum allowable power. For instance, if the
desired accuracy is 1°C, and the rated D.C. of the device selected is 5 mW/°C,
adjusting the specified D.C. rating in the power equation to 0.5 mW/°C compensates
for self-heating error and effectively predicts the maximum power the device can
dissipate without significantly affecting the desired accuracy. The resulting maximum
power that should be applied would be calculated as 1°C*0.5mW/°C = 0.5mW.
NTC
DISC & CHIP
- Selection Process
Select R Value
Determine R @ T
Calculate DEV for R @ T
Evaluate Power Rating (D.C.)
Review T.C. Requirements
NTC Standard Chip Thermistor Specifications
Part Num ber
05CA101K
05CA151K
05CA201K
05CA251K
05CA301K
05CA401K
05CA501K
05CB102K
05CB152K
05CB202K
05CB302K
05CB402K
05CB502K
05CC802K
05CC103K
05CC153K
05CC203K
05CC253K
05CC303K
05CE104K
05CE154K
05CE204K
05CE304K
05CE404K
05CE504K
Resistance
@25°C
(Ohm s) ±10%
100
150
200
250
300
400
500
1,000
1,500
2,000
3,000
4,000
5,000
8,000
10,000
15,000
20,000
25,000
30,000
100,000
150,000
200,000
300,000
400,000
500,000
R-T
Curve
A
A
A
A
A
A
A
B
B
B
B
B
B
C
C
C
C
C
C
E
E
E
E
E
E
THK
(in.)
0.020
0.025
0.030
0.040
0.050
0.070
0.080
0.020
0.025
0.030
0.050
0.070
0.080
0.020
0.025
0.035
0.050
0.060
0.075
0.030
0.045
0.060
0.090
0.120
0.150
D.C.
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
T.C.
2
2
2
2
3
3
3
2
2
2
3
3
3
2
2
2
3
3
3
2
2
2
3
3
3
www.rtie.com/category-s/91.htm
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18/11/2013
Disc & Chip Thermistors
Maximum Temperature rating: 150°C
NTC Standard Disc Thermistor Specifications
Part
Num ber
5DA4R0K
5DA5R0K
2DA100K
3DA100K
5DA100K
3DA150K
2DA200K
1DA300K
2DA300K
1DA500K
2DA500K
3DB500K
4DB500K
1DA101K
2DB101K
2DB151K
2DB201K
2DB301K
3DB301K
1DB501K
2DB501K
4DC501K
1DB102K
2DC102K
3DC102K
1DB202K
2DC202K
2DC302K
3DC302K
2DC402K
1DC502K
2DC502K
1DC103K
2DE103K
3DE103K
2DE203K
2DE303K
1DE503K
2DE503K
1DE104K
Resis.
@25°C
(Ohm s) ±10%
4
5
10
10
10
15
20
30
30
50
50
50
50
100
100
150
200
300
300
500
500
500
1,000
1,000
1,000
2,000
2,000
3,000
3,000
4,000
5,000
5,000
10,000
10,000
10,000
20,000
30,000
50,000
50,000
100,000
R-T
Curve
A
A
A
A
A
A
A
A
A
A
A
B
B
A
B
B
B
B
B
B
B
C
B
C
C
B
C
C
C
C
C
C
C
E
E
E
E
E
E
E
D (in.)
0.50
0.50
0.20
0.30
0.50
0.30
0.20
0.10
0.20
0.10
0.20
0.30
0.40
0.10
0.20
0.20
0.20
0.20
0.30
0.10
0.20
0.40
0.10
0.20
0.30
0.10
0.20
0.20
0.30
0.20
0.10
0.20
0.10
0.20
0.30
0.20
0.20
0.10
0.20
0.10
THK (in.)
0.065
0.080
0.025
0.060
0.150
0.090
0.050
0.020
0.075
0.030
0.120
0.025
0.045
0.060
0.025
0.035
0.050
0.070
0.150
0.030
0.120
0.070
0.060
0.035
0.080
0.120
0.070
0.100
0.210
0.125
0.040
0.160
0.080
0.040
0.085
0.075
0.115
0.050
0.190
0.095
D.C.
14
15
7
8
17
8
7
3
7
3
7
8
9
3
7
7
7
7
9
3
7
9
3
7
8
4
7
7
10
7
3
8
4
7
8
7
7
3
7
3
T.C.
60
70
18
48
120
55
20
5
25
6
30
35
50
10
18
19
20
25
75
6
30
65
10
18
48
14
25
30
90
32
8
36
12
17
48
20
25
6
30
9
Leads
AWG#
22
22
24
24
22
24
24
28
24
28
24
24
22
28
24
24
24
24
24
28
24
22
28
24
24
28
24
24
24
24
28
24
28
24
24
24
24
28
24
28
S
(in.)
0.330
0.330
0.100
0.100
0.330
0.100
0.100
0.070
0.100
0.070
0.100
0.100
0.330
0.070
0.100
0.100
0.100
0.100
0.100
0.070
0.100
0.330
0.070
0.100
0.100
0.070
0.100
0.100
0.100
0.100
0.070
0.100
0.070
0.100
0.100
0.100
0.100
0.070
0.100
0.070
Maximum temperature rating: 150° C
Standard resistance tolerances:
J=5%, K=10%, L=15%, M=20%
Other resistance tolerances available.
www.rtie.com/category-s/91.htm
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Disc & Chip Thermistors
NTC
DISC & CHIP
- Configuration Options
DISC
Leaded Insulated/Non-insulated
Without Leads
Pre-formed Leads
CHIP
Standard size 0.050" x 0.050" x "T"
Leaded
Epoxy Coated
Un-coated
NTC Resistance/Temperature Conversion Tables
Tem p. °C
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
R-T Curve
Temp. Coeff. ( @ 25°C)
Beta, ß
R-T Curve
RT/R25
43.0
31.9
24.3
18.6
14.4
11.3
8.93
7.10
5.69
4.56
3.68
2.99
2.45
2.02
1.68
1.42
1.18
1.00
0.854
0.732
0.628
0.537
0.464
0.403
0.350
0.305
0.267
0.236
0.208
0.183
0.163
0.145
0.130
0.117
0.105
0.0943
0.0852
0.0771
0.0700
0.0636
0.0579
0.0529
0.0483
A
DEV
R-T Curve
RT/R25
75.0
54.1
39.7
29.2
21.7
16.4
12.5
9.58
7.42
5.75
4.50
3.55
2.82
2.26
1.83
1.48
1.22
1.00
0.828
0.689
0.576
0.482
0.406
0.343
0.292
0.247
0.212
0.182
0.157
0.137
0.120
0.105
0.0920
0.0812
0.0723
0.0641
0.0569
0.0508
0.0455
0.0408
0.0368
0.0332
0.0300
A
-3.3%/°C
3000°K
B
DEV
6.6
6.1
5.6
5.2
4.7
4.3
3.8
3.4
3.0
2.6
2.2
1.9
1.5
1.2
0.8
0.5
0.2
0.0
0.4
0.7
1.0
1.3
1.5
1.8
2.0
2.3
2.5
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
4.9
5.1
5.3
5.4
5.5
R-T Curve
RT/R25
140.5
96.4
67.0
47.2
33.7
24.3
17.7
13.0
9.71
7.30
5.53
4.23
3.27
2.54
1.99
1.57
1.25
1.00
0.806
0.653
0.533
0.437
0.360
0.299
0.249
0.208
0.175
0.148
0.126
0.107
0.0916
0.0787
0.0679
0.0588
0.0511
0.0445
0.0389
0.0342
0.0301
0.0265
0.0235
0.0208
0.0185
B
-3.9%/°C
3530°K
C
DEV
6.6
6.1
5.6
5.2
4.7
4.3
3.8
3.4
3.0
2.6
2.2
1.9
1.5
1.2
0.8
0.5
0.2
0.0
0.4
0.7
1.0
1.3
1.5
1.8
2.0
2.3
2.5
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
4.9
5.1
5.3
5.4
5.5
C
-4.4%/°C
3965°K
R-T Curve E
RT/R25
DEV
131.0
97.5
66.6
45.5
32.3
23.0
16.5
12.0
8.79
6.51
4.86
3.71
2.79
2.13
1.65
1.28
1.00
0.787
0.623
0.496
0.398
0.320
0.259
0.211
0.172
0.141
0.114
0.0962
0.0799
0.0666
0.0588
0.0468
0.0395
0.0333
0.0283
0.0241
0.0205
0.0176
0.0151
0.0130
0.0112
0.0101
E
-4.9%/°C
4500°K
7.6
6.9
6.2
5.6
5.0
4.4
3.7
3.1
2.5
2.0
1.6
1.1
0.6
0.0
0.6
1.1
1.6
2.0
2.5
3.0
3.4
3.8
4.2
4.6
4.9
5.3
5.6
6.0
6.3
6.7
7.0
7.3
7.6
7.9
8.2
8.4
8.6
9.0
9.3
7.6
6.9
6.2
5.6
5.0
4.4
3.7
3.1
2.5
2.0
1.6
1.1
0.6
0.0
0.6
1.1
1.6
2.0
2.5
3.0
3.4
3.6
4.2
4.6
4.9
5.3
5.6
6.0
6.3
6.7
7.0
7.3
7.6
7.9
8.2
8.4
8.6
9.0
9.3
NTC Resistance/Temperature Curve Characteristics
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18/11/2013
R@0°C/R@50°C
R@25°C/R@125°C
Disc & Chip Thermistors
5.3±5%
13.0
6.9±3%
19.8
9.1±3%
29.4
11.6±5%
48.7
Resistance at Temperature:
To determine the nominal resistance value of a thermistor at a specified temperature, multiply its R
T
/R
25
value
for the desired temperature and R-T curve from the table above by its nominal resistance value at 25°C. For
instance, the nominal resistance value at 80°C for a thermistor with part number 1DC103K is 10,000 times
0.126, the R
T
/R
25
value in R-T Curve C table above, or 1,260 ohms.
Resistance Tolerances:
The standard resistance tolerance at 25°C for RTI's NTC thermistors is ±10% and is indicated in its part
number by the addition of the suffix K. However, RTI's thermistors may also be supplied with other resistance
tolerances. To determine a thermistor's resistance tolerance at a temperature other than 25°C, add the
appropriate DEV value from the R-T Curve table above to its resistance tolerance at 25°C. For instance, the
resistance tolerance at 80°C for a thermistor with part number 1DC103K is ±10% ±3.0%, the DEV value from
the R-T Curve C table above or ±13%.
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