Cleveland Motion Controls DIN Rail Amplifier MWI-13261 Ultra Series Isolated REV BA - Manual (Page 5)

MAN-13261 R EV BA DIN R AIL A MPLIFIER , MWI-13261 U LTRA
1 P
RODUCT
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VERVIEW
1.1 G ENERAL D ESCRIPTION
The Ultra Series DIN Rail amplifier (Isolated) provides a complete signal conditioning solution for amplifying and
reporting signals from a pair of strain gage-based load cells. Either semiconductor or foil-based load cells can be
used and the Ultra Series Isolated DIN Rail amplifier offers an added benefit of an isolation amplifier stage to
provide galvanic isolation.
Because the output stage is free to float, be aware of voltage differences on the output
side of the amplifier with respect to protective earth ground.
The isolated Ultra Series DIN Rail amplifier has a separate ground reference (common) for the output signals. The
ground used by the output circuits is electrically separate from the ground reference for the combined 24V supply
and strain-gage signal conditioning.
The Ultra Series DIN Rail amplifier uses a dedicated Instrumentation Amplifier (IA) for each transducer channel.
The IA stage amplifies the millivolt level signals generated by the load cells, while effectively rejecting common-
mode noise. A wide range of switch selectable gains can be used to provide the most appropriate level of initial
amplification. Low drift Surface Mount Technology (SMT) components, Multi-layer Printed Circuit Boards (PCB)
and optimum circuit topologies are incorporated to promote load cell signal integrity.
A summing amplifier stage combines the left and right IA channels. The gain of this stage is adjustable over a 10:1
range to allow span calibration of the analog outputs. To improve rejection of “out of band” signals, the summing
stage is followed by a DC accurate 2-pole active filter.
A precision voltage source is provided for exciting the strain gage elements in the inter-connected load cells (tension
transducers). The circuit includes a short circuit current limit feature to protect the amplifier in the event of mis-
wiring. Output voltage is selectable to either of the following:
• 5.0 VDC
• 10.0 VDC
The use of galvanic isolation can aid in reducing noise pickup caused by ground loops in the field wiring and
accommodates limited voltage gradients between input and output sections of the application wiring.
The output circuits (+/- 10 volt, 4-20mA and the meter outputs) are galvanically isolated with respect to the
combined 24VDC supply terminals and the load cell interface circuits. The isolation is accomplished by using a
servo-stabilized linear opto-isolator stage. The output circuitry is powered by an isolated DC to DC converter.
The final analog tension signal is available in a variety of forms. The un-damped output signal can be provided
from a +/-10V analog buffer stage, as well as a standard 4-20 mA current loop stage. The voltage supply for the
current loop bias is internally provided. The current loop scaling has been specially designed so that minor negative
excursions of the tension signal can continue to be reported as currents below 4 mA.
A damped (low pass filtered) version of the tension signal is available for driving displays or recording devices. The
damping is switch selectable for a cutoff frequency of either 0.3 Hz or 3.7 Hz. Damping is useful for improving the
readability, effectively masking higher frequency fluctuations superimposed on the tension signal. This damped
output stage can be configured to be either:
• +/- 2V analog output - intended primarily for driving Digital Panel Meters (DPM).
• +/-1 mA current source - when configured as the current source, the 1 mA output is
typically used to drive D’Arsonval style analog meters.
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