Functional Description - PEP Modular Computers Modular Computers RS485 User Manual

Chapter 5 Analog Modules

5.2.5 Functional Description

Figure 5.2.5.1: SM-PT100 Schematic Diagram
User Interface
PT100 Sensor , 4-wire Input
400 A
The SM-PT100 has provision for 4 sets of 4-wire PT100 sensors driven by
an on-board generated 400 A constant current source. The differential
analog input consists of a channel multiplexer, operational amplifier voltage
feedback impedance converter and a high-resolution 16-bit delta-sigma
converter. 1000V DC system isolation is provided by an optoisolated DC/DC
converter while system flexibility is provided by a 256 bytes of serial
EEPROM for ID number, production and board-specific calibration data.
Two front-panel LEDs show the conversion/calibration activity.
The PT100 is a platinum resistance, which at 0ºC has a resistance of 100
and conforms to the international DIN IEC 751 standard for Industrial
Platinum Resistance Thermometer Sensors. Two classes A and B exist under
this standard with class B experiencing a slightly worse initial error.
Figure 5.2.5.2 Supported Sensor Connections
Red
Pt 100/ /2
March 12, 1996
R
L
CUR
SUPPLY LINE
400 A
IN+
SENSE LINE
SENSE LINE
IN-
SUPPLY LINE
AGND
R
L
White Red Red
©1996 PEP Modular Computers GmbH
SMART I/O User's Manual
System Interface
White Red
Pt 100/ /3
LED
Driver
Serial System
I/O Interface
Red White Red
Pt 100/ /4
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