HTM1735LF – Temperature and Relative Humidity Module
HTM1735LF HPC035_K www.meas-spec.com May 2008
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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.
RT NTC resistance in Ω at temperature T in K
RN NTC resistance in Ω at rated temperature T in K
T, TN Temperature in K
β Beta value, material specific constant of NTC
e Base of natural logarithm (e=2.71828)
c The exponential relation only roughly describes the actual characteristic of an NTC thermistor can, however,
as the material parameter β 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.
d 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 MEAS-France
Application Note HPC106 “Low power NTC measurement”.
• Temperature look-up table
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
×= N
TT
NT eRR
11
β
Temp Resistance Max Deviation Temp Resistance Max Deviation Temp Resistance Max Deviation Temp Resistance Max Deviation
(°C) (Ω)
(Ω)
(°C) (Ω)
(Ω)
(°C) (Ω
(Ω)
(°C
(Ω
(Ω)
-30 144790 16636 -2 33100 2230 26 9600 300 54 3360 213
-29 136664 15444 -1 31557 2078 27 9218 300 55 3237 208
-28 129054 14343 030029 1932 28 8853 299 56 3126 204
-27 121925 13325 128627 1799 29 8506 297 57 3019 200
-26 115243 12383 227299 1675 30 8178 296 58 2917 197
-25 109030 11516 326042 1560 31 7866 294 59 2819 193
-24 103115 10705 424852 1452 32 7568 292 60 2720 189
-23 97565 9953 523773 1355 33 7283 290 61 2629 185
-22 92354 9257 622708 1261 34 7011 287 62 2542 182
-21 87460 8612 721698 1174 35 6734 284 63 2458 178
-20 82923 8020 820739 1093 36 6484 281 64 2378 175
-19 78581 7463 919829 1017 37 6244 278 65 2304 171
-18 74497 6947 10 18959 946 38 6015 275 66 2229 168
-17 70655 6468 11 18128 879 39 5796 271 67 2158 165
-16 67039 6023 12 17338 817 40 5575 267 68 2089 161
-15 63591 5606 13 16588 759 41 5373 264 69 2022 158
-14 60381 5222 14 15876 705 42 5180 260 70 1960 155
-13 57356 4865 15 15207 654 43 4995 257 71 1898 152
-12 54503 4533 16 14569 607 44 4817 253 72 1839 149
-11 51813 4225 17 13962 563 45 4636 248 73 1782 146
-10 49204 3932 18 13384 522 46 4473 245 74 1727 143
-9 46767 3662 19 12834 484 47 4316 241 75 1673 140
-8 44467 3411 20 12280 447 48 4166 237 76 1622 138
-7 42296 3177 21 11777 413 49 4021 233 77 1573 135
-6 40247 2960 22 11297 382 50 3874 229 78 1526 132
-5 38279 2756 23 10840 353 51 3737 225 79 1480 130
-4 36455 2568 24 10404 325 52 3606 221 80 1432 127
-3 34731 2393 25 10000 300 53 3481 217