Cleveland Motion Controls Classic Series DIN Rail Amplifier with Isolated Output MWI-13467 REV CA - Manual (Page 5)

MAN-13467 R EV CA C LASSIC S ERIES A MPLIFIER W / I SOLATED O UTPUTS
Page 5 of 30
1 P RODUCT O VERVIEW
1.1 G ENERAL D ESCRIPTION
The Classic 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 Classic 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 Classic 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 Classic Series DIN Rail amplifier uses an Instrumentation Amplifier (IA) to amplify the signal from a pair of
half-bridge transducers. 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 variable gain stage further amplifies the output of the instrumentation amplifier. The gain of this stage is
adjustable over a 10:1 range to allow span calibration of the analog outputs.
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 is provided from a
+/-10V analog buffer stage.
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.