Pepper-computer Modular Computers RS485 Bedienungsanleitung PDF herunterladen (Seite 217)

SMART I/O User’s Manual

Chapter 5 Analog Modules

Multiplexer

A/D

Converter

System

Interface

Serial

I/O

Impedance

Converter

Thermo Sensor

LED

Driver

IN+

IN-

AGND

SENSE LINE

SHIELD LINE

SENSE LINE

External PT100 Sensor, 2-wire Cold Junction Input

TMP+

TMP-

SUPPLY/SENSE LINE

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).

5.3.5 Functional Description

Figure 5.3.5.1: SM-THERM Schematic Diagram

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Pepper-computer Modular Computers RS485 Bedienungsanleitung Seite 217