Impulse DSCT36 - Manual

DIN Rail Mount Two-WireTransmitters DSCT
For information call 800-444-7644 206
DSCT36
Potentiometer Input Transmitters
Figure 1: DSCT36 Block Diagram
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Features
• Interfaces to Potentiometers up to 10k Ω
• 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
• ±0.03% Accuracy
• ±0.01% Linearity
• Easily Mounts on Standard DIN Rail
• CSA and FM Approvals Pending
• CE Compliant
Description
Each DSCT36 potentiometer input transmitter provides a single channel of
potentiometer input which is filtered, isolated, amplified, 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.
Potentiometer excitation is provided from the transmitter using a precision current
source. The excitation current is small (less than 0.26mA) which minimizes self-
heating of the potentiometer. Lead compensation is achieved by matching two
current paths which cancels the effects of lead resistance.
Special input and output circuits on the DSCT36 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. Signal and loop 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 ±10% to accommodate
situations where fine-tuning is desired. The adjustments are made using
potentiometers located under the front panel label and are non-interactive for
ease of use.