DS3820RTDD - RTD Input Module

SPECIFICATIONS:

Part Number: DS3820RTDD
Manufacturer: General Electric
Series: Mark IV
Product Type: RTD Input Module
Supported Sensors: Pt100, Pt200, Pt500
Sampling Interval: 10 ms � 1000 ms
Resolution: 14�16 bits
Excitation Current: 0.1 mA
Channel Update Time: 50 ms � 500 ms
Isolation: 500 V � 1500 V
Typical Power Consumption: 2 W � 5 W
Operating Temperature: 0 �C to +60 �C
Size: 3.5 x 0.8 x 2.5 in
Repair: 3-7 Days
Availability: In Stock
Weight: 2 lbs
Country of Origin: United States

FUNCTIONAL DESCRIPTION:

DS3820RTDD is an RTD Input Module manufactured and designed by General Electric as part of the Mark IV Series used in GE Speedtronic Gas Turbine Control Systems. The RTD input module is an intelligent block transfer module that interfaces analog input signals with any Allen�Bradley programmable controllers that have block transfer capability. Block transfer programming moves input data words from the module�s memory to a designated area in the processor data table in a single scan. It also moves configuration words from the processor data table to module memory. The input module is a single-slot module and requires no external power supply. After scanning the analog inputs, the input data is converted to a specified data type in a digital format to be transferred to the processor�s data table on request. The block transfer mode is disabled until this input scan is complete. Consequently, the minimum interval between block transfer reads (50ms) is the same as the total input update time for each analog input module.

FEATURES OF RTD INPUT MODULE:

The RTD input module senses up to 6 RTD signals at its inputs and converts them to corresponding temperature or resistance in 4�4-digit BCD or 16�bit binary format. The module can be configured for 100 ohm platinum or 10 ohm copper RTDs, or other sensor types such as 120 ohm nickel RTDs. Temperature ranges are available in degrees C or F. Values can also be measured in ohms. When using 10 ohm copper RTDs, it is necessary to dedicate your module for exclusive use with 10 ohm copper RTDs. You can configure the module to accept signals from any combination of 100-ohm platinum and other types of non�copper RTDs. Both cases are determined by block transfer write (BTW) selection. The processor transfers data to and from the module using block transfer write (BTW) and block transfer read (BTR) instructions in your ladder diagram program. These instructions let the processor obtain input values and status from the module, and let you establish the module�s mode of operation.

• The processor transfers your configuration data and calibration values to the module using a block transfer write instruction.
• External devices generate analog signals that are transmitted to the module.
• The module converts analog signals into binary or BCD format and stores these values until the processor requests their transfer.
• When instructed by your ladder program, the processor performs a read block transfer of the values and stores them in a data table.
• The processor and module determine that the transfer was made without error and that the input values are within the specified range.
• Your ladder program can use and/or move the data (if valid) before it is overwritten by the transfer of new data in a subsequent transfer.

CONFIGURATION:

The Real-Time Sampling (RTS) mode enables precise time-based calculations in PLC applications such as PID control and totalization by scanning and updating inputs at a user-defined interval (T) instead of the default rate. During each sampling period, the module ignores all Block Transfer Read (BTR) requests and transfers data only once at the end of the interval; subsequent requests are disregarded until new data is available. If a BTR is not completed before the next sampling cycle, a time-out bit is set in the BTR status area to indicate that at least one data set was missed (the exact number is unknown), and this bit resets upon successful completion of the next BTR.

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FREQUENTLY ASKED QUESTIONS:

What types of RTD sensors are supported?

The module supports Pt100, Pt200, Pt500, Pt1000, and Ni-type RTDs. It can handle 2-wire, 3-wire, or 4-wire configurations depending on the module design.

How does the module handle open or shorted RTDs?

Built-in diagnostics detect open circuits, short circuits, over- and under-range conditions. Status bits are provided per channel to signal fault conditions to the PLC.

What excitation current is applied to RTD sensors?

The module applies a precision excitation current between 0.1�1 mA, minimizing self-heating and ensuring accurate resistance measurement.

What happens if multiple channels exceed the measurement range simultaneously?

Channels exceeding their range set over-range status bits individually. The module continues measuring valid channels without interrupting overall operation.