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
β (
−
)
T
TN
RT = RN ∗ e
RT
RN
NTC resistance in ꢀ at temperature T in K
NTC resistance in ꢀ at rated temperature T in K
T, TN Temperature in K
ꢃ
e
Beta value, material specific constant of NTC
Base of natural logarithm (e=2.71828)
Å
The exponential relation only roughly describes the actual characteristic of an NTC thermistor can, however, as
the material parameter ꢃ 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.
Ç
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
Tem p Resistance
Tem p Resistance
Tem p Resistance
Tem p Resistance
(°C)
-40
-39
-38
-37
-36
-35
-34
-33
-32
-31
-30
-29
-28
-27
-26
-25
-24
-23
-22
-21
-20
-19
-18
-17
-16
-15
-14
-13
-12
-11
-10
-9
(Ω )
(°C)
0
1
2
3
4
5
6
7
(Ω )
(°C)
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
(Ω )
(°C)
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
(Ω )
1669
1622
1578
1535
1493
1452
1413
1375
1338
1303
1268
1234
1202
1170
1139
1110
1081
1053
1026
999
195652
184917
174845
165391
156513
148171
140330
132958
126022
119494
113347
107565
102116
96978
92132
87559
83242
79166
75316
71677
68237
64991
61919
59011
56258
53650
51178
48835
46613
44506
42506
40600
38791
37073
35442
33892
32420
31020
29689
28423
27219
26076
24988
23951
22963
22021
21123
20267
19450
18670
17926
17214
16534
15886
15266
14674
14108
13566
13049
12554
12081
11628
11195
10780
10382
10000
9634
9284
8947
8624
8315
8018
7734
7461
7199
6948
6707
6475
6253
5834
5636
5445
5262
5086
4917
4754
4597
4446
4301
4161
4026
3896
3771
3651
3535
3423
3315
3211
3111
3014
2922
2834
2748
2666
2586
2509
2435
2364
2294
2228
2163
2100
2040
1981
1925
1870
1817
1766
1716
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Delta Temperature corresponding to NTC deviation (°C)
2,5
2,0
1,5
1,0
0,5
0,0
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
974
949
925
902
880
858
837
816
796
777
758
-40
-20
0
20
40
60
80
100
Temperature (°C)
-8
-7
-6
-5
-4
-3
-2
-1
0.1°C tolerance on Resistance Measurement
6039
________________________________________________________________________________________
Humirel HTG3500 Series Datasheet / HPC123 Rev B November 2007
5
HUMIREL [ Humirel ]
