PEP Modular Computers Modular Computers RS485 User Manual page 188

SMART I/O User's Manual
The two- and three-wire measurement methods shown in figure 5.2.5.2 are
not compensated and will experience errors due to line-resistances. The best
and recommended method is the 4-wire system shown in figure 5.2.5.1.
which eliminates all line resistances automatically. The sense lines, being
connected to a high impedance differential amplifier (10M ), introduce
almost zero error resulting from line-resistances.
Table 5.2.5.2 shows the deviation from the required temperature for both
class A and class B PT100 sensors.
Table 5.2.5.2 Tolerances between Class A and Class B Sensors
Temperature
C
-200
-100
0
100
200
300
400
500
600
650
700
800
850
Driver software running under OS-9 supplies linearization data for use with
DIN standard PT100 sensors. The on-board EEPROM contains board
specific calibration data for self calibration purposes.
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Tolerance
Class A
C
0.55 0.24
0.35 0.14
0.15 0.06
0.35 0.13
0.55 0.20
0.75 0.27
0.95 0.33
1.15 0.38
1.35 0.43
1.45 0.46
– –
– –
– –
©1996 PEP Modular Computers GmbH
Chapter 5 Analog Modules
Class B
C
1.3 0.56
0.8 0.32
0.3 0.12
0.8 0.30
1.3 0.48
1.8 0.64
2.3 0.79
2.8 0.93
3.3 1.06
3.6 1.13
3.8 1.17
4.3 1.28
4.6 1.34
March 12, 1996