Impulse SCM5B34 User Manual download pdf

For information call 800-444-7644

Isolated Analog Signal Conditioning Products

SCM5B

SCM5B34

Linearized 2- or 3-Wire RTD Input Modules

▲

Features

 Interfaces to 100Ω Platinum, 10Ω Copper,

or 120

Ω Nickel RTDs

 Linearizes RTD Signal

 High Level Voltage Outputs

 1500Vrms Transformer Isolation

 ANSI/IEEE C37.90.1 Transient Protection

 Input Protected to 240VAC Continuous

 160dB CMR

 95dB NMR at 60Hz, 90dB at 50Hz

 CSA Certified, FM Approved, CE and ATEX

Compliant

 Mix and Match SCM5B Types on Backpanel

Figure 1: SCM5B34 Block Diagram

Each SCM5B34 RTD input module provides a single channel of RTD input

which is filtered, isolated, amplified, linearized, and converted to a high level

analog voltage output (Figure 1). This voltage output is logic switch controlled,

which allows these modules to share a common analog bus without the

requirement of external multiplexers.

The SCM5B modules are designed with a completely isolated computer side

circuit which can be floated to ±50V from Power Common, pin 16. This complete

isolation means that no connection is required between I/O Common and Power

Common for proper operation of the output switch. If desired, the output switch

can be turned on continuously by simply connecting pin 22, the Read-Enable

pin, to I/O Common, pin 19.

RTD excitation is provided from the module by two matched current sources.

When using a three-wire RTD, this method allows an equal current to flow in

each RTD lead, which cancels the effects of lead resistances. The excitation

currents are very small (0.25mA for 100

Ω Pt and 120Ω Ni, and 1.0mA for 10Ω

Cu) which minimizes self-heating of the RTD.

Signal filtering is accomplished with a six-pole filter which provides 95dB of

normal-mode-rejection at 60Hz and 90dB at 50Hz. Two poles of this filter are

on the field side of the isolation barrier, and the other four are on the computer

side. After the initial field-side filtering, the input signal is chopped by a proprietary

chopper circuit. Isolation is provided by transformer coupling, again using a

proprietary technique to suppress transmission of common mode spikes or

surges. The module is powered from +5VDC, ±5%.

A special input circuit on the SCM5B34 modules provides protection against

accidental connection of power-line voltages up to 240VAC.

Description

1 2

Summary of Contents

Page 1 - Description

For information call 800-444-764412Isolated Analog Signal Conditioning ProductsSCM5BSCM5B34Linearized 2- or 3-Wire RTD Input Modules▲ Features Inte

Page 2 - Ordering Information

Visit our website www.dataforth.com13Isolated Analog Signal Conditioning ProductsSCM5BSCM5BSpecificationsModuleSCM5B34Typical at TA=+25°C and +5V powe

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Impulse SCM5B34 User Manual

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