Analog input module SCM7B34

voltagecurrentfor RTD

Each SCM7B34 or SCM7B34N isolated linearized 2- or 3-wire RTD input module accepts a single channel of 100 ohm Platinum (a = 0.00385) or 120 ohm Nickel (a = 0.00672) RTD input and produces an input voltage in response to a low-level current excitation. The input signal is filtered, isolated, amplified, linearized, and converted to a high-level analog voltage for output to the process control system. These SCM7B34 isolated linearized 2- or 3-wire RTD input module incorporate a five-pole filtering approach to maximize both time and frequency response by taking advantage of both Thomson (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 response to the low-level current excitation signal, the RTD 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.