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Linearized 2- or 3-Wire RTD Input Modules with Voltage-Output, Bandwidth 4 Hz

Each SCM7B34N RTD input module accepts a single channel of 100 Ω Platinum (α = 0.00385) or 120 Ω Nickel (α = 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 modules 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.

Linearization is achieved by creating a non-linear transfer function through the module itself. This non-linear transfer function is configured at the factory and is designed to be equal and opposite to the specific RTD non-linearity. Lead compensation is achieved by matching two current paths thus cancelling the effects of lead resistance.

Modules accept a wide 14 - 35 VDC power supply range (+ 24 VDC nominal). Their compact packages (2.13" x1.705" x0.605" max) save space and are ideal for high channel density applications. They are designed for easy DIN rail mounting using any of the “-DIN” backpanels.

Circuit diagram Dataforth SCM7B34N

Block Diagram SCM7B34N

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2 Modules for Type SCM7B34N:

SCM7B34N-01 0°C to +300°C SCM7B34N Isolated Linearized 2- or 3-Wire RTD Input Module with Voltage-Output
SCM7B34N-02 0°C to +200°C SCM7B34N Isolated Linearized 2- or 3-Wire RTD Input Module with Voltage-Output


  • Input: RTD
  • Output: 1 V … 5 V / 0 V … 5 V / 0 V … 10 V
  • Bandwidth 3 Hz
  • Isolation 1500 Vrms
  • Input protection 120 Vrms
  • Accuracy ± 0.15% (typ.), ± 0.3% (max.)
  • Conformity ± 0.06%...± 0.07% (typ.), ± 0.12%...± 0.14% (max.)
  • ANSI/IEEE C37.90.1 Input protection
  • CMR 160dB
  • True 2-way isolation
  • NMR: 80/85dB at 50/60Hz
  • Power Supply 14 to 35 VDC
  • Operating Temperature Range -40°C … +85°C
  • Mix and Match Types on Backpanels possible
  • Dimensions 54.1 x 43.3 x 15.4 mm
  • Optional DIN Rail Mounting
  • CSA certified, CE and ATEX compliant
  • Wide range of accessories
  • Special Solutions on request