Impulse DSCT47 - Manual

DIN Rail Mount Two-WireTransmitters DSCT
For information call 800-444-7644 210
DSCT47
Linearized Thermocouple Input Transmitters
Figure 1: DSCT47 Block Diagram
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Features
• Interfaces to Types J, K, T, E, R, S, B, and N
Thermocouples
• Linearizes Thermocouple Signal
• Process Current Output
• 1500Vrms Transformer Isolation
• ANSI/IEEE C37.90.1 Transient Protection
• Input and Output Protected to 240VAC
Continuous
• Up to 60V Loop Voltage
• 160dB CMR
• 85dB NMR at 60Hz, 80dB at 50Hz
• ±0.10% Accuracy
• Easily Mounts on Standard DIN Rail
• CSA and FM Approvals Pending
• CE Compliant
Description
Each DSCT47 thermocouple input transmitter provides a single channel of
thermocouple input which is filtered, isolated, amplified, linearized, and
converted to a process current output (Figure 1). 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 are on the process loop 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.
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 thermocouple non-linearity.
The DSCT47 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 and screw
terminals on the transmitter. Upscale open thermocouple detection is provided
by circuitry. Downscale indication can be implemented by installing a 47M Ω ,
±20% resistor between screw terminals 6 (+IN) and 8 (-EXC) on the input
terminal block.
Special input and output circuits on the DSCT47 transmitters provide protection
against accidental connection of power-line voltages up to 240VAC and against
transient events as defined by ANSI/IEEE C37.90.1. Loop power lines are
secured to the module using screw terminals, which are in pluggable terminal
blocks for ease of system assembly and reconfiguration. Transmitter zero and
span settings are adjustable up to ±3%. The adjustments are made using
potentiometers located under the front panel label and are non-interactive for
ease of use.