Analog Voltage Input Signal Conditioners, Narrow Bandwidth DSCT37
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Each DSCT37 non-linearized thermocouple input transmitter provides a singlechannel of thermocouple input which is filtered, isolated, amplified, and converted to a process current output (Figure 1). Signal filtering is accomplishedwith a five-pole filter, which provides 85dB of normal-mode rejection at 60Hz and80dB at 50Hz.An anti-aliasing pole is located on the field side of the isolation barrier, and the other four are on the process loop side. After the initial field-sidefiltering, the input signal is chopped by a proprietary chopper circuit. Isolation isprovided by transformer coupling, again using a proprietary technique to suppress transmission of common mode spikes or surges.The DSCT37 can interface to eight industry standard thermocouple types:J, K, T, E, R, S, B and N. Each transmitter is cold-junction compensated to correct for parasitic thermocouples formed by the thermocouple wire andscrew terminals on the transmitter. Upscale open thermocouple detection isprovided by circuitry. Downscale indication can be implemented by installing a 47M > ?Interfaces to Types J, K, T, E, R, S, B, and NThermocouples?Process Current Output?1500Vrms Transformer Isolation?ANSI/IEEE C37.90.1 Transient Protection?Input and Output Protected to 240VACContinuous?Up to 60V Loop Voltage ?160dB CMR?85dB NMR at 60Hz, 80dB at 50Hz?0.05% Accuracy?ѱ0.01% Linearity?Easily Mounts on Standard DIN Rail ?CSA and FM Approvals Pending?CE Compliant Ω , 20% resistor between screw terminals 6 (+IN) and 8 (-EXC) on theinput terminal block.Special input and output circuits on the DSCT37 transmitters provide protectionagainst accidental connection of power-line voltages up to 240VAC and againsttransient events as defined by ANSI/IEEE C37.90.1. Loop power lines aresecured to the module using screw terminals, which are in pluggable terminal blocks for ease of system assembly and reconfiguration. Transmitter zero andspan settings are adjustable up to ѱ10%. The adjustments are made usingpotentiometers located under the front panel label and are non-interactive forease of use. > Figure 1: DSCT37 Block Diagram