Pepper-computer Modular Computers RS485 Bedienungsanleitung PDF herunterladen (Seite 187)

SMART I/O User’s Manual

Chapter 5 Analog Modules

5.2.5 Functional Description

Figure 5.2.5.1: SM-PT100 Schematic Diagram

The SM-PT100 has provision for 4 sets of 4-wire PT100 sensors driven by

an on-board generated 400µA 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 100Ω

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

Multiplexer

A/D

Converter

System

Interface

LED

Driver

Impedance

Converter

Serial

I/O

PT100 Sensor , 4-wire Input

CUR

IN+

IN-

AGND

400 µA

SENSE LINE

SUPPLY LINE

SENSE LINE

User Interface System Interface

Pt 100/ /2

Red White

Pt 100/ /3

Red WhiteRed

Pt 100/ /4

Red WhiteRed Red

1 2 ... 182 183 184 185 186 187 188 189 190 191 192 ... 319 320

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