________________________________________________________________________________________

Humirel HTG3500 Series Datasheet / HPC123 Rev B November 2007

5

Temperature Sensor

Typical temperature output

Depending on the needed temperature measurement range and associated accuracy, we suggest two methods to access

to the NTC resistance values.

)

1

1

(

N

T

T

N

T

e

R

R

−

∗

=

β

NTC resistance in

at temperature T in K

NTC resistance in

at rated temperature T in K

Temperature in K

Beta value, material specific constant of NTC

e

Base of natural logarithm (e=2.71828)

The exponential relation only roughly describes the actual characteristic of an NTC thermistor can, however, as

the material parameter in reality also depend on temperature. So this approach is suitable for describing a restricted

range around the rated temperature or resistance with sufficient accuracy.

For practical applications, a more precise description of the real R/T curve may be required. Either more

complicated approaches (e.g. the Steinhart-Hart equation) are used or the resistance/temperature relation as given in

tabulation form. The below table has been experimentally determined with utmost accuracy for temperature increments

of 1 degree.

Actual values may also be influenced by inherent self-heating properties of NTCs. Please refer to Humirel Application

Note HPC106-0 “Low power NTC measurement”.

Temperature Look-Up Table in pulsed mode or for a 3.3 voltage supply

0.1°C tolerance on Resistance Measurement

"% $

"& $

"% $

"& $

"% $

"& $

"% $

"& $

-40

195652

0

27219

40

5834

80

1669

-39

184917

1

26076

41

5636

81

1622

-38

174845

2

24988

42

5445

82

1578

-37

165391

3

23951

43

5262

83

1535

-36

156513

4

22963

44

5086

84

1493

-35

148171

5

22021

45

4917

85

1452

-34

140330

6

21123

46

4754

86

1413

-33

132958

7

20267

47

4597

87

1375

-32

126022

8

19450

48

4446

88

1338

-31

119494

9

18670

49

4301

89

1303

-30

113347

10

17926

50

4161

90

1268

-29

107565

11

17214

51

4026

91

1234

-28

102116

12

16534

52

3896

92

1202

-27

96978

13

15886

53

3771

93

1170

-26

92132

14

15266

54

3651

94

1139

-25

87559

15

14674

55

3535

95

1110

-24

83242

16

14108

56

3423

96

1081

-23

79166

17

13566

57

3315

97

1053

-22

75316

18

13049

58

3211

98

1026

-21

71677

19

12554

59

3111

99

999

-20

68237

20

12081

60

3014

100

974

-19

64991

21

11628

61

2922

101

949

-18

61919

22

11195

62

2834

102

925

-17

59011

23

10780

63

2748

103

902

-16

56258

24

10382

64

2666

104

880

-15

53650

25

10000

65

2586

105

858

-14

51178

26

9634

66

2509

106

837

-13

48835

27

9284

67

2435

107

816

-12

46613

28

8947

68

2364

108

796

-11

44506

29

8624

69

2294

109

777

-10

42506

30

8315

70

2228

110

758

-9

40600

31

8018

71

2163

-8

38791

32

7734

72

2100

-7

37073

33

7461

73

2040

-6

35442

34

7199

74

1981

-5

33892

35

6948

75

1925

-4

32420

36

6707

76

1870

-3

31020

37

6475

77

1817

-2

29689

38

6253

78

1766

-1

28423

39

6039

79

1716

Delta Temperature corresponding to NTC deviation (°C)

0,0

0,5

1,0

1,5

2,0

2,5

-40

-20

0

20

40

60

80

100

Temperature (°C)