Functional Description - PEP Modular Computers Modular Computers RS485 User Manual

Chapter 5 Analog Modules

5.3.5 Functional Description

Figure 5.3.5.1: SM-THERM Schematic Diagram
Thermo Sensor
External PT100 Sensor, 2-wire Cold Junction Input
The SM-THERM allows four sets of three-wire thermocouples to be con-
nected together with one additional PT100 element used as a cold junction
point reference. The differential analog input consists of a channel multi-
plexer, operational amplifier voltage feedback impedance converter and a
high-resolution 16-bit delta-sigma converter. 1000V system isolation is
provided by an optoisolated DC/DC converter while system flexibility is
provided by 256-bytes of serial EEPROM for ID number, production and
board specific calibration data. Two front-panel LEDs show the conversion/
calibration activity.
In principle any thermocouple conforming to the DIN43710 or IEC584
specifications can be connected. Sensor breakdown recognition is performed
by the software which also caters for and corrects absolute temperature
readings with a connected cold junction point (PT100).
March 12, 1996
AGND
SHIELD LINE
IN+
SENSE LINE
IN-
SENSE LINE
SUPPLY/SENSE LINE
TMP+
TMP-
SUPPLY/SENSE LINE
©1996 PEP Modular Computers GmbH
SMART I/O User's Manual
Serial
I/O
LED
Driver
System
Interface
5
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