Datasheet

MAX31865
RTD-to-Digital Converter
19Maxim Integrated
ADC Code = 15-bit ADC results from RTD Data registers
(01h–02h)
R
REF
= Resistance of the reference resistor
Once the resistance of the RTD is known, the well-
defined resistive properties of the selected RTD can be
used to determine temperature by either calculations or
lookup tables.
In the typical case of a PT100 RTD with a 400I high
precision low drift reference resistor, Table 9 shows
examples of temperature and resistance values with the
corresponding ADC code results.
Table 9. Temperature Example for PT100 with 400I R
REF
TEMPERATURE
(°C)
RTD RESISTANCE
(ω)
RTD DATA REG
(01h-02h) (hex)
ADC CODE (dec)
ADC CODE/32-256
(°C)
-200 18.52 0BDAh 1517 -208.59
-175 29.22 12B4h 2394 -181.19
-150 39.72 196Ch 3254 -154.31
-125 50.06 200Ah 4101 -127.84
-100 60.26 2690h 4936 -101.75
-75 70.33 2D04h 5762 -75.94
-50 80.31 3366h 6579 -50.41
-40 84.27 35EEh 6903 -40.28
-30 88.22 3876h 7227 -30.16
-20 92.16 3AFCh 7550 -20.06
-10 96.09 3D7Eh 7871 -10.03
0 100.00 4000h 8192 0.00
10 103.90 4280h 8512 10.00
20 107.79 44FCh 8830 19.94
30 111.67 4778h 9148 29.88
40 115.54 49F2h 9465 39.78
50 119.40 4C6Ah 9781 49.66
60 123.24 4EE0h 10096 59.50
70 127.08 5154h 10410 69.31
80 130.90 53C6h 10723 79.09
90 134.71 5636h 11035 88.84
100 138.51 58A4h 11346 98.56
110 142.29 5B12h 11657 108.28
120 146.07 5D7Ch 11966 117.94
130 149.83 5FE4h 12274 127.56
140 153.58 624Ch 12582 137.19
150 157.33 64B0h 12888 146.75
160 161.05 6714h 13194 156.31
170 164.77 6974h 13498 165.81
180 168.48 6BD4h 13802 175.31
190 172.17 6E30h 14104 184.75
200 175.86 708Ch 14406 194.19
225 185.01 7668h 15156 217.63
250 194.10 7C3Ah 15901 240.91