Impulse SCM5B38 - Manual

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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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