Analog input module SCM7B36

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Each SCM7B36 isolated potentiometer input module provides a single channel of resistance input which is filtered, isolated, amplified, and converted to a high level analog voltage output. The SCM7B36 isolated potentiometer input module interfaces to slidewires and potentiometers in both two and three wire configuration and incorporates a five-pole filtering approach to maximize both time and frequency response by taking advantage of both Bessel and Butterworth characteristics. One pole of the filter is on the field side of the isolation barrier; four are on the process control system side. In the 3-Wire configuration, lead resistance compensation is provided if the resistance of the "x" lead is closely equivalent to that of the "+" lead. Internal to the SCM7B36 isolated potentiometer input module, measurement error due to lead resistance is cancelled. In response to the low level current excitation, and after initial field-side filtering, the input signal is chopped by a proprietary chopper circuit and transferred across the transformer isolation barrier, suppressing transmission of common mode spikes and surges. The signal is then reconstructed and filtered for process control system output.