IC670ALG620 RTD Analog Input Module

The RTD Analog Input Module (IC670ALG620) accepts inputs from 4 independent 3-wire and/or 4-wire platinum, nickel, nickel/iron, or copper RTDs.

Module features include:

Selectable resistance measurements in tenths of ohms, tenths of degrees Fahrenheit, or tenths of degrees Celsius

Individual channel configuration

Selectable resistance ranges: 0 – 500 ohms and 0 – 3000 ohms

Selectable RTD input as resistance or temperature (Celsius or Fahrenheit)

Reports high/low, underrange/overrange, open wire, and input short alarms.

Uses optional discrete inputs and outputs for status and control.

Two data acquisition rates based on 50 Hz and 60 Hz line frequencies

Configurable channel activation

Power Sources： No loop power is required for this module. The excitation current for the RTDs is provided by the module, which automatically matches the excitation current to each configured RTD type.

LED： A single indicator shows module status:

ON: normal operation
.  Intermittent flashing: module fault
OFF: loss of backplane power or fatal fault

Module Operation：

IC670ALG620 RTD Input Module accepts four inputs from three-wire or four-wire RTDs and converts the input level to a digital value. Input spans support a variety of RTD types, as listed in the Module Specifications section.

The analog/digital converter reads the voltage generated by each of the four inputs. The A/D converter converts the differential measurement into a binary value (15 bits plus sign), which is read by the block's microprocessor. The microprocessor sets the gain required in the analog/digital converter for each input. The gain is based on the RTD type that has been configured for that input.

The microprocessor selects the input by means of a solid-state, optically coupled multiplexer. Three measurements are made for each input: Excitation current, RTD resistance, including field wire drop, and field wire drop. From these three measurements, the module calculates the RTD resistance. A DC/DC converter circuit isolates the field side from the logic circuits.

Host Interface：

IC670ALG620 RTD Input module has the following data types:

4 analog inputs (4 words)

32 bits of discrete input data for module and channel status (use of this data is optional)

8 bits of discrete output data for fault clearing to the module (also optional)

Analog output data defaults to a length of 0, and should NOT be used for most applications.

A starting reference and length in the Bus Interface Unit (BIU) data tables for each data type is selected during module configuration. Depending on the configuration that has been set up for each RTD, the input data can be reported as tenths of ohms, tenths of degrees Fahrenheit, or tenths of degrees Celsius.

This module exchanges data with a BIU in the same manner as other types of I/O modules-it provides all its input data and status bits when requested by the BIU, and receives fault-clearing commands from the BIU via its assigned output bits. Note that the BIU can be configured not to send status data over the network.

The module can also be configured for "Group" data transfer with the BIU or with other intelligent devices in the same Field Control station. Group data transfer, and the steps for configuring it, are described in the Bus Interface Unit User's Manual.

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