Temperature sensor

The temperature sensor circuitry consists of a serial connection of a normal and a NTC resistor. The NTC sensor is from Murata and some part details are shown in table "Table 1", more information can be obtained from the manufacturers web-site.
Table 1. NTC characteristics
Global part number NCP18WF104J03RB
Resistance (25°C) 100 kΩ ± 5%
B-Constant (25/50°C) 4250 K ± 2%
B-Constant (25/80°C) 4303 K
B-Constant (25/85°C) 4311 K
B-Constant (25/100°C) 4334 K
Following table shows the temperature vs. resistance characteristic. The values are available from Murata in the datasheet of the NTC. Approximations can be used to model the temperature vs. resistance characteristic, for example the B parameter and the Steinhart-Hart equations. The coefficients for both formulas can be calculated from the values in Table 2.
Table 2. Resistance vs. temperature
Temp. [°C] NTC resistance [kΩ] Temp. [°C] NTC resistance [kΩ] Temp. [°C] NTC resistance [kΩ] Temp. [°C] NTC resistance [kΩ]
-30 2197.225 0 357.012 30 79.222 60 22.224
-29 2055.558 1 338.006 31 75.675 61 21.374
-28 1923.932 2 320.122 32 72.306 62 20.561
-27 1801.573 3 303.287 33 69.104 63 19.782
-26 1687.773 4 287.434 34 66.061 64 19.036
-25 1581.881 5 272.500 35 63.167 65 18.323
-24 1483.100 6 258.426 36 60.415 66 17.640
-23 1391.113 7 245.160 37 57.797 67 16.986
-22 1305.413 8 232.649 38 55.306 68 16.360
-21 1225.531 9 220.847 39 52.934 69 15.760
-20 1151.037 10 209.710 40 50.677 70 15.184
-19 1081.535 11 199.196 41 48.528 71 14.631
-18 1016.661 12 189.268 42 46.482 72 14.101
-17 956.080 13 179.890 43 44.533 73 13.592
-16 899.481 14 171.028 44 42.675 74 13.104
-15 846.579 15 162.651 45 40.904 75 12.635
-14 797.111 16 154.726 46 39.213 76 12.187
-13 750.834 17 147.232 47 37.601 77 11.757
-12 707.524 18 140.142 48 36.063 78 11.344
-11 666.972 19 133.432 49 34.595 79 10.947
-10 628.988 20 127.080 50 33.195 80 10.566
-9 593.342 21 121.066 51 31.859 81 10.200
-8 559.931 22 115.368 52 30.584 82 9.848
-7 528.602 23 109.970 53 29.366 83 9.510
-6 499.212 24 104.852 54 28.203 84 9.185
-5 471.632 25 100.000 55 27.091 85 8.873
-4 445.772 26 95.398 56 26.028 86 8.572
-3 421.480 27 91.032 57 25.013 87 8.283
-2 398.652 28 86.889 58 24.042 88 8.006
-1 377.193 29 82.956 59 23.113 89 7.738
When the internal reference VCC/1.6 is used and the ADC is measuring in signed single ended mode the codes in the table below can be read from the ADC at the various temperatures. The calculation is based on the above table.
Table 3. ADC codes vs. temperature (signed single ended mode with internal VCC/1.6 reference)
ADC input [V] Temp. [°C] ADC codes ADC input [V] Temp. [°C] ADC codes
2.076 -14 2047 0.347 38 345
2.030 -13 2014 0.334 39 332
1.983 -12 1968 0.321 40 319
1.936 -11 1921 0.309 41 307
1.889 -10 1875 0.297 42 295
1.841 -9 1828 0.286 43 283
1.794 -8 1781 0.275 44 273
1.747 -7 1734 0.264 45 262
1.700 -6 1687 0.254 46 252
1.653 -5 1640 0.244 47 243
1.606 -4 1594 0.235 48 233
1.560 -3 1548 0.226 49 225
1.514 -2 1503 0.218 50 216
1.469 -1 1458 0.209 51 208
1.425 0 1414 0.202 52 200
1.380 1 1370 0.194 53 193
1.337 2 1327 0.187 54 185
1.294 3 1285 0.180 55 178
1.252 4 1243 0.173 56 172
1.211 5 1202 0.167 57 165
1.171 6 1162 0.161 58 159
1.131 7 1123 0.155 59 154
1.093 8 1084 0.149 60 148
1.055 9 1047 0.144 61 142
1.018 10 1010 0.138 62 137
0.982 11 975 0.133 63 132
0.947 12 940 0.128 64 127
0.913 13 907 0.124 65 123
0.880 14 874 0.119 66 118
0.848 15 842 0.115 67 114
0.817 16 811 0.111 68 110
0.787 17 781 0.107 69 106
0.758 18 752 0.103 70 102
0.730 19 724 0.100 71 99
0.702 20 697 0.096 72 95
0.676 21 671 0.093 73 92
0.650 22 645 0.090 74 89
0.626 23 621 0.086 75 86
0.602 24 597 0.083 76 83
0.579 25 575 0.081 77 80
0.557 26 553 0.078 78 77
0.535 27 531 0.075 79 75
0.515 28 511 0.073 80 72
0.495 29 491 0.070 81 70
0.476 30 472 0.068 82 67
0.458 31 454 0.065 83 65
0.440 32 437 0.063 84 63
0.423 33 420 0.061 85 61
0.407 34 404 0.059 86 59
0.391 35 388 0.057 87 57
0.376 36 373 0.055 88 55
0.361 37 359 0.053 89 53
Parent topic: Peripherals