Impulse SCM5B38 User Manual

Scm5b38, Strain gage input modules, wide bandwidth, Scm5b

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Isolated Analog Signal Conditioning Products

SCM5B

SCM5B38

Strain Gage Input Modules, Wide Bandwidth

Description

Each SCM5B38 Strain Gage input module provides a single channel of Strain

Gage input which is filtered, isolated, amplified, 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.
The SCM5B38 can interface to full-bridge or half-bridge transducers with a

nominal resistance of 100

Ω

to 10k

Ω

. A matched pair of bridge-completion

resistors (to ±1mV at +10V excitation) allows use of low cost half-bridge or

quarter-bridge transducers (Figures 2, 3, 4). The 10kHz bandwidth allows

measurement of high speed processes such as vibration analysis.
Strain Gage excitation is provided from the module by a very stable 10V

or 3.333V source. The excitation supply is fully isolated, allowing the amplifier

inputs to operate over the full range of the excitation voltage. This feature

offers significant flexibility in real world applications. Full scale sensitivities of

2mV/V, 3mV/V or 10mV/V are offered as standard. With 10V excitation, this

results in ±20mV, ±30mV or ±100mV full scale input range producing ± 5V full

scale output.
The input signal is processed through a pre-amplifier on the field side of the

isolation barrier. This pre-amplifier has a gain-bandwidth product of 5MHz and

is bandwidth limited to 10kHz. After amplification, the input signal is chopped by

a proprietary chopper circuit. Isolation is provided by transformer coupling,

Figure 1: SCM5B38 Block Diagram

again using a proprietary technique to suppress transmission of common mode

spikes or surges. The module is powered from +5VDC, ±5%.
Special input circuits on the SCM5B38 module provide protection of the signal

inputs and the isolated excitation supply up to 240VAC.

Features

Interfaces to 100

Ω

Thru 10k

Ω

, Full-Bridge,

Half-Bridge, or Quarter-Bridge Strain Gages

High Level Voltage Output
1500Vrms Transformer Isolation
ANSI/IEEE C37.90.1 Transient Protection
Input Protected to 240VAC Continuous
Fully Isolated Excitation Supply
100dB CMR
10kHz Signal Bandwidth
±0.03% Accuracy
±0.01% Linearity
±1µV/°C Drift
CSA Certified, FM Approved, CE and ATEX

Compliant

Mix and Match SCM5B Types on Backpanel

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