SCM7B37 Non-Linearized Isolated Thermocouple Input Modules
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Isolated Process Control Signal Conditioning Products SCM7B37 Non-Linearized Isolated Thermocouple Input Modules Description SCM7B37 non-linearized modules accept a single channel of input from Type J, K, T, E, R, S, or B thermocouples. The signal is filtered, isolated, amplified, and converted to a high-level analog voltage for output to the process control system (Figure 1). Cold junction compensation (CJC) is performed using an NTC thermistor (see “Additional SCM7B Part Numbers” section for P/N and AN701 for further information) externally mounted under the field-side terminal block on the backpanel (Figure 1). Open thermocouple detection is upscale using a 30nA current source in the input circuitry. 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. Features • Interfaces to Type J, K, T, E, R, S, and B Thermocouples • Provides High-Level Voltage Outputs • 1500Vrms Transformer Isolation • Accuracy, ±0.03% of Span Typical, ±0.1% Max • ANSI/IEEE C37.90.1 Transient Protection • Input Protected to 120Vrms Continuous • Noise, 500µVp-p (5MHz), 250µVrms (100kHz) After the 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. Modules accept a wide 14 - 35VDC power supply range (+24VDC 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. • 85dB NMR at 60Hz, 80dB at 50Hz • Easy DIN Rail Mounting • CE and ATEX Compliant Refer to AN701 for Vout to temperature conversion information Figure 1: SCM7B37 Block Diagram ©1995-2011 Dataforth Corporation, All Rights Reserved ISO9001:2008-Registered QMS

Isolated Process Control Signal Conditioning Products Ordering Information Input Signal Range Bias Current Resistance Normal Power Off Overload Protection Continuous Transient Output Signal Range(2) Effective Available Power(2) Resistance Protection Voltage/Current Limit CMV (Input-to-Output) Continuous Transient CMRR (50 or 60Hz) Accuracy(3) Linearity(4) Stability (–40°C to +85°C) Gain Input Offset Zero Suppression Output Offset Noise Peak at 5MHz B/W RMS at 10Hz to 100kHz B/W Peak at 0.1Hz to 10Hz B/W CJC Accuracy(6), +5°C to +45°C ambient Open Input Response Open Input Detection Time...