Impulse DSCA37 - Manual

High Performance Signal Conditioners DSCA
For information call 800-444-7644 140
DSCA37
Thermocouple Input Signal Conditioners
Description
Each DSCA37 thermocouple input module provides a single channel of
thermocouple input which is filtered, isolated, amplified, and converted to a high
level voltage output. Signal filtering is accomplished with a five-pole filter which
provides 85dB of normal-mode-rejection at 60Hz and 80dB at 50Hz. An
anti-aliasing pole is located on the field side of the isolation barrier, and the other
four poles are on the system side. After the initial field-side filtering, the input signal
is chopped by a proprietary chopper circuit. Isolation is provided by transformer
coupling, again using a proprietary technique to suppress transmission of
common mode spikes or surges.
The DSCA37 can interface to eight industry standard thermocouple types: J, K,
T, E, R, S, B and N. Each module has cold junction compensation to correct for
parasitic thermocouples formed by the thermocouple wire and input screw
terminals on the module. Upscale open thermocouple detection is provided
by internal circuitry. Downscale indication can be implemented by installing a
47M Ω , ±20% resistor between screw terminals 6 and 8 on the input terminal block.
Module output is either voltage or current. For current output models a dedicated
loop supply is provided at terminal 3 (+OUT) with loop return located at terminal
4 (-OUT). The system-side load may be either floating or grounded.
Special input circuits provide protection against accidental connection of
power-line voltages up to 240VAC and against transient events as defined by
ANSI/IEEE C37.90.1. Protection circuits are also present on the signal output
and power input terminals to guard against transient events and power reversal.
Power lines are secured to the module using screw terminals which are in
pluggable terminal blocks for ease of system assembly and reconfiguration.
The modules have excellent stability over time and do not require recalibration,
however, zero and span settings are adjustable up to ±5% to accommodate
situations where fine-tuning is desired. The adjustments are made using potentiom-
eters located under the front panel label and are non-interactive for ease of use.
Features
• Interfaces to Types J, K, T, E, R, S, B, and N
Thermocouples
• Industry Standard Output of Either 0-10V,
0-20mA, or 4-20mA
• 1500Vrms Transformer Isolation
• ANSI/IEEE C37.90.1 Transient Protection
• Input Protected to 240VAC Continuous
• True 3-Way Isolation
• Wide Range of Supply Voltage
• 160dB CMR
• 85dB NMR at 60Hz, 80dB at 50Hz
• ±0.05% Accuracy
• ±0.01% Linearity
• Easily Mounts on Standard DIN Rail
• C-UL-US Listed
• CE and ATEX Compliant
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Figure 1: DSCA37 Block Diagram