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OM5-WBS
Strain Gage Input Modules, Wide Bandwidth
FEATURES
● INTERFACES TO 100Ω THRU 10kΩ,FULL-BRIDGE, HALF-BRIDGE,
OR QUARTER-BRIDGE STRAIN GAGES
● HIGH LEVEL VOLTAGE OUTPUTS
● 1500Vrms TRANSFORMER ISOLATION
●
ANSI/IEEE C37.90.1-1989
TRANSIENT PROTECTION
● INPUT PROTECTED TO 240VAC CONTINUOUS
● FULLY ISOLATED EXCITATION SUPPLY
● 100dB CMR
● 10kHz SIGNAL BANDWIDTH
● ± 0.08% ACCURACY
● ± 0.02% LINEARITY
● ± 1µV/°C DRIFT
● CSA CERTIFIED, FM APPROVED, CE COMPLIANT
● MIX AND MATCH OM5 TYPES ON BACKPANEL
DESCRIPTION
Each OM5-WBS 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 OM5-WBS 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 OM5-WBS can interface to full-bridge or half-bridge transducers with
a nominal resistance of 100Ω to 10kΩ. 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, again using a proprietary technique to suppress
transmission of common mode spikes or surges. The module is powered
from +5VDC, ±5%.
Special input circuits provide protection of the signal inputs and the
isolated excitation supply up to 240VAC.
FIGURE 1. OM5-WBS Block Diagram.
–V
LPF
+In
–In
–EXC
Backpanel
Term Block
6
5
3
Surge
Suppression
and
Protection
+V
Isolated
Field-Side
Power
Power
Oscillator
Isolated
Computer-Side
Power
V
OUT
20
19
22
I/O Common
RD EN\
+5V
17
16
Power
Common
4
3
2
1
+EXC
–V
+V
4
Isolated
Excitation
Source
1
2
Strain
Gage
Isochopper™
Amplifier
Pat Pending
LPF