Impulse DSCT34 User Manual download pdf

DIN Rail Mount Two-WireTransmitters

DSCT

For information call 800-444-7644

204

DSCT34

Linearized 2- or 3-Wire RTD Input Transmitters

Figure 1: DSCT34 Block Diagram

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Features

 Interfaces to 100Ω Platinum or 120Ω

Nickel RTDs

 Linearizes RTD 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

 ±0.1% Accuracy

 ±0.025% Conformity

 Easily Mounts on Standard DIN Rail

 CSA and FM Approvals Pending

 CE Compliant

Description

Each DSCT34 RTD input transmitter provides a single channel of RTD 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.

RTD excitation is provided from the transmitter using a precision current source.

The excitation currents are very small (0.26mA max for 100Ω Pt and 120Ω Ni)

which minimizes self-heating of the RTD. 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 specific RTD non-linearity. Lead compensation is achieved by matching

two current paths thus canceling the effects of lead resistance.

The specifications listed are for a 3-wire connection. A 2-wire connection of the

RTD to the module is also possible and is achieved by adding a jumper between

pin 5 (+EXC) and pin 6 (+IN) on the terminal block and connecting the RTD leads

between pin 6 (+IN) and pin 7 (-IN). The 2-wire connection nullifies the lead

resistance compensation feature of the module.

Special input and output circuits on the DSCT34 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 ±3% 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.

1 2

Summary of Contents

Page 1 - Description

DIN Rail Mount Two-WireTransmittersDSCTFor information call 800-444-7644204DSCT34Linearized 2- or 3-Wire RTD Input TransmittersFigure 1: DSCT34 Block

Page 2 - Ordering Information

DSCTVisit our website www.dataforth.com205DIN Rail Mount Two-Wire TransmittersDSCTSpecificationsInput Range -200°C to +850°C (100Ω Pt)-80°C to +320°C

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Impulse DSCT34 User Manual

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