Pepper Computer RS485, RS232 user manual Tolerances between Class a and Class B Sensors

SMART I/O User’s Manual Chapter 5 Analog Modules

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 (10MΩ), 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		Tolerance
°C
	Class A		Class B
	°C	Ω	°C	Ω
-200	± 0.55	± 0.24	± 1.3	± 0.56
-100	± 0.35	± 0.14	± 0.8	± 0.32
0	± 0.15	± 0.06	± 0.3	± 0.12
100	± 0.35	± 0.13	± 0.8	± 0.30
200	± 0.55	± 0.20	± 1.3	± 0.48
300	± 0.75	± 0.27	± 1.8	± 0.64
400	± 0.95	± 0.33	± 2.3	± 0.79
500	± 1.15	± 0.38	± 2.8	± 0.93
600	± 1.35	± 0.43	± 3.3	± 1.06
650	± 1.45	± 0.46	± 3.6	± 1.13
700	–	–	± 3.8	± 1.17
800	–	–	± 4.3	± 1.28
850	–	–	± 4.6	± 1.34

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.

Page 5 - 32 ©1996 PEP Modular Computers GmbH March 12, 1996