8
APPENDIX D - THERMISTOR LINEARIZATION
A thermistor (temperature sensing device) is normally encapsulated with all Geokon
vibrating wire sensors. Use an ohmmeter to measure the resistance (usually the green
and white leads from the gage cable). The following equation or Table 2 can be used to
determine the temperature in degrees centigrade.
Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3
Steinhart and Hart Log Equation:
T
A
B LnR
C LnR
=
+
+
−
1
273 2
3
(
)
(
)
.
where: T
=
Temperature in
°
C.
LnR
=
Natural Log of Thermistor Resistance
A
=
1.4051
×
10
-3
B
=
2.369
×
10
-4
C
=
1.019
×
10
-7
Note: Coefficients calculated over -50
°
to +150
°
C. span.
Ohms Temp Ohms Temp Ohms Temp Ohms Temp Ohms Temp
201.1K -50 16.60K -10 2417
+
30
525.4
+
70
153.2
+
110
187.3K
-49
15.72K -9 2317 31 507.8 71 149.0 111
174.5K
-48
14.90K -8 2221 32 490.9 72 145.0 112
162.7K
-47
14.12K -7 2130 33 474.7 73 141.1 113
151.7K
-46
13.39K -6 2042 34 459.0 74 137.2 114
141.6K
-45
12.70K -5 1959 35 444.0 75 133.6 115
132.2K
-44
12.05K -4 1880 36 429.5 76 130.0 116
123.5K
-43
11.44K -3 1805 37 415.6 77 126.5 117
115.4K
-42
10.86K -2 1733 38 402.2 78 123.2 118
107.9K
-41
10.31K -1 1664 39 389.3 79 119.9 119
101.0K
-40 9796 0 1598 40 376.9 80 116.8 120
94.48K -39 9310
+
1
1535 41 364.9 81 113.8 121
88.46K
-38 8851 2 1475 42 353.4 82 110.8 122
82.87K
-37 8417 3 1418 43 342.2 83 107.9 123
77.66K
-36 8006 4 1363 44 331.5 84 105.2 124
72.81K
-35 7618 5 1310 45 321.2 85 102.5 125
68.30K
-34 7252 6 1260 46 311.3 86 99.9 126
64.09K
-33 6905 7 1212 47 301.7 87 97.3 127
60.17K
-32 6576 8 1167 48 292.4 88 94.9 128
56.51K
-31 6265 9 1123 49 283.5 89 92.5 129
53.10K
-30 5971 10 1081 50 274.9 90 90.2 130
49.91K
-29 5692 11 1040 51 266.6 91 87.9 131
46.94K
-28 5427 12 1002 52 258.6 92 85.7 132
44.16K
-27 5177 13 965.0 53 250.9 93 83.6 133
41.56K
-26 4939 14 929.6 54 243.4 94 81.6 134
39.13K
-25 4714 15 895.8 55 236.2 95 79.6 135
36.86K
-24 4500 16 863.3 56 229.3 96 77.6 136
34.73K
-23 4297 17 832.2 57 222.6 97 75.8 137
32.74K
-22 4105 18 802.3 58 216.1 98 73.9 138
30.87K
-21 3922 19 773.7 59 209.8 99 72.2 139
29.13K
-20 3748 20 746.3 60 203.8 100 70.4 140
27.49K
-19 3583 21 719.9 61 197.9 101 68.8 141
25.95K
-18 3426 22 694.7 62 192.2 102 67.1 142
24.51K
-17 3277 23 670.4 63 186.8 103 65.5 143
23.16K
-16 3135 24 647.1 64 181.5 104 64.0 144
21.89K -15
3000 25
624.7 65 176.4 105 62.5 145
20.70K
-14 2872 26 603.3 66 171.4 106 61.1 146
19.58K
-13 2750 27 582.6 67 166.7 107 59.6 147
18.52K
-12 2633 28 562.8 68 162.0 108 58.3 148
17.53K
-11 2523 29 543.7 69 157.6 109 56.8 149
55.6
150
Table 2 - Thermistor Resistance vs. Temperature
