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10k Thermistor Look Up Table for an I/Net 7756 (lower board)

Issue

Table needed for linearizing a 10K thermistors for an I/Net 7756 (lower board)

Environment

 7756 (lower board)

Cause

Thermistors require the use of a look up table to linearize the data.

Resolution

Thermistor Inputs on a PCU 7756 (lower board)

  1. Enter the Temperature data in °C (First Column - 31 entries)
  2. Enter the corresponding resistance data in Ohms (Second column - 31 entries)
  3. Enter the dissipation constant in milliwatts per °C: 2
  4. Low Temperature :     -22.11°F       -30.06°C
  5. High Temperature:    247.92°F      119.95°C
  6. Point Value in °F:   M=0.00412         b=-22.1138
  7. Point Value in °C:  M=0.00228913   b=--30.0632065

Look Up Table:

 

°C Ohms Current Self Htg Adj °C Adj °F VDC Counts Adj Cts
120 389 0.000481 0.045052 119.95 247.92 0.187217 1227 65535
100 680 0.000468 0.074521 99.93 211.87 0.318352 2086 56785
90 917 0.000458 0.096177 89.90 193.83 0.419987 2752 52407
80 1258 0.000444 0.12407 79.88 175.78 0.558714 3662 48027
70 1753 0.000425 0.158633 69.84 157.71 0.745767 4887 43643
60 2489 0.0004 0.199471 59.80 139.64 0.996477 6530 39257
55 3045 0.000383 0.223671 54.78 130.60 1.167114 7646 37062
50 3602 0.000368 0.243359 49.76 121.56 1.32407 8677 34869
45 4368 0.000348 0.264484 44.74 112.52 1.520045 9962 32676
40 5326 0.000326 0.283435 39.72 103.49 1.73757 11387 30483
35 6691 0.0003 0.300218 34.70 94.46 2.004374 13136 28292
30 8056 0.000277 0.308878 29.69 85.44 2.230837 14620 26104
28 8777 0.000266 0.311174 27.69 81.84 2.337168 15317 25229
26 9572 0.000255 0.312351 25.69 78.24 2.44533 16025 24355
25 10000 0.00025 0.3125 24.69 76.44 2.5 16384 23918
24 10450 0.000244 0.312349 23.69 74.64 2.555012 16744 23481
22 11420 0.000233 0.311127 21.69 71.04 2.665733 17470 22608
20 12490 0.000222 0.308669 19.69 67.44 2.77679 18198 21735
18 13680 0.000211 0.304953 17.70 63.85 2.888514 18930 20863
16 15000 0.0002 0.3 15.70 60.26 3 19661 19992
14 16470 0.000189 0.29383 13.71 56.67 3.111069 20388 19121
12 18090 0.000178 0.286579 11.71 53.08 3.220007 21102 18250
10 19900 0.000167 0.278241 9.72 49.50 3.327759 21808 17380
8 21920 0.000157 0.268921 7.73 45.92 3.433584 22502 16510
6 24180 0.000146 0.258715 5.74 42.33 3.537156 23181 15641
0 32660 0.000117 0.224329 -0.22 31.60 3.827942 25086 13035
-4 36200 0.000108 0.211999 -4.21 24.42 3.917749 25675 11293
-10 55340 0.0000765 0.162028 -10.16 13.71 4.234772 27753 8694
-14 69000 0.0000633 0.138199 -14.14 6.55 4.367089 28620 6957
-20 97130 0.0000467 0.105789 -20.11 -4.19 4.533277 29709 4350
-30 177200 0.0000267 0.063207 -30.06 -22.11 4.732906 31017 0

This spreadsheet is for a thermistor rated at 10,000 ohms at 25°C.

  1. Install a 10K Ohm Resistor in the "B" terminal (consult the TCON for the controller you are using for details)
  2. This look up table program is based on using 31 entries
  3. The data points do not have to be evenly spaced

Click here to download this in pdf format.

For the look up table to the

7716, 7718, 7728 and a 7756 (upper board), see Lessons Learned Article #7206

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