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