Each SCM7B36 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 module interfaces to slidewires and potentiometers in both two or 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 module, measurement error due to lead resistance is canceled.
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.
Six standard input resistance ranges are offered, from 100 Ohm to 10k Ohm, with three output ranges available: 0-5V, 1-5V, and 0-10V. Modules accept a wide 14-35VDC power supply range (+24VDC nominal). Their compact packages (2.13″ x 1.705″ x 0.605″ max.) save space and are ideal for high channel density applications. They are designed for easy DIN rail mounting using any of Dataforth’s “-DIN” backpanels.
