PRODUCT INFORMATION
Product Overview
The Allen-Bradley 1794-IR8 is a FLEX I/O analog input module designed for temperature monitoring. This module functions as a resistance temperature detector input unit with eight dedicated channels. Each input channel supports nominal signal ranges from 1 to 433 ohms. The unit provides 16-bit resolution across 435 ohms. An excitation current of 718.36 microamps powers connected RTD sensor elements.
The module connects to standard 1794 terminal base units including 1794-TB2, 1794-TB3, and 1794-TB3T. Backplane current draw equals 20 milliamps from the FLEX I/O Flexbus. Maximum power dissipation reaches 3.0 watts at 31.2 volts DC. Thermal dissipation is 10.2 BTU per hour at 31.2 volts DC. Data is stored in 16-bit two's complement or unipolar offset binary format.
TECHNICAL DATA
Technical Specifications
| Parameter | Specification |
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| Product Line | Flex I/O 1794 |
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| UPC | 612598137824 |
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| Weight | 0.56 lbs (0.26 kg) |
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| Resolution | 16 bits across 435 ohms |
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| Product Description | Flex IO 8-Channel RTD Input Module |
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| Number of Inputs | 8 |
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| Terminal base | 1794-TB2, 1794-TB3 and 1794-TB3T |
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| Sensors supported | 100 ? Pt ? = 0.00385 Euro (-200…+870 °C) 100 ? Pt ? = 0.003916 U.S. (-200…+630 °C) 200 ? Pt ? = 0.00385 Euro (- 200…+630 °C) 500 ? Pt ? = 0.00385 U.S. (-200…+630 °C) 100 ? Nickel ? = 0.00618 (-60…+250 °C) 120 ? Nickel ? = 0.00672 (-60…+250 °C) 200 ? Nickel ? = 0.00618 (-60…+250 °C) 500 ? Nickel ? = 0.00618 (-60…+250 °C) 10 ? Copper ? = 0.00427 (- 200…+260 °C). |
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| RTD Excitation Current | 718.36?A |
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| Accuracy | Without calibration, at low humidity: Normal mode: 0.05% full scale (max) Enh. mode: 0.01% full scale (typical) |
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| Data Format | 16-bit 2's complement or offset binary (unipolar) |
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| System Throughput | Normal Mode: Programmable from 28ms/channel to 325ms/channel 325ms (1 channel scanned) 2.6s (8 channels scanned) - default Enhanced Mode: Programmable from 56ms/channel to 650ms/channel 650ms (1 channel scanned) - default 2.925s (8 channels scanned) |
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| Mounting | DIN Rail |
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| Wire Size | Determined by installed terminal base |
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| Operating Temperature | 0 to 55 C (32 to 131 F) |
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| Storage Temperature | –40…85 °C (–40…185 °F) |
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| Vibration | 5g @ 10 to 500 Hz |
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| Operating Shock | 30 g |
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| Inputs | 8 Channels |
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| Nominal Input Ranges | 1 to 433 ohms |
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| Isolation Voltage | 850 Volts DC |
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| Normal Mode Noise Rejection | -60 DB at 60 Hertz |
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| Channel Bandwidth | 0 to 2.62 Hertz |
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| Normal Mode System Throughput | 325 milliseconds |
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| Flexbus Current | 20mA |
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| Power Dissipation | 3 Watts at 31.2 Volts DC maximum |
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| Thermal Dissipation | 10.2 BTU/hour at 31.2 Volts DC maximum |
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| UNSPSC | 32151602 |
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TECHNICAL INFORMATION
Features
- Provides eight RTD input channels with 16-bit resolution across 435 ohms.
- Supplies an RTD excitation current of 718.36 microamps to connected sensors.
- Converts input signals into 16-bit two's complement or offset binary unipolar formats.
- Delivers 0.05 percent full-scale accuracy in normal mode without calibration.
- Delivers 0.01 percent typical full-scale accuracy in enhanced mode at low humidity.
- Draws 20 milliamps of current from the Flexbus backplane.
TECHNICAL INFORMATION
Applications
- Industrial RTD temperature measurement systems using FLEX I/O architectures.
- Temperature signal acquisition using platinum, nickel, and copper RTD sensors.
TECHNICAL INFORMATION
Connections / Interfaces
- Plugs into 1794-TB2, 1794-TB3, and 1794-TB3T terminal base units.
- Connects to the local adapter via the integrated Flexbus backplane.
- Receives field wiring through the terminals of the installed base unit.
TECHNICAL INFORMATION
Installation Guidelines
- Mount the assembly directly on a standard DIN rail.
- Snap the module securely onto an installed 1794 terminal base.
- Maintain operating ambient temperatures between 0 and 55 degrees Celsius.
- Operate the unit with nominal 24 volts DC user power.
TECHNICAL INFORMATION
Configuration Guidelines
- Configure channel throughput between normal mode and enhanced mode settings.
- Normal mode throughput provides programmable scan times from 28 to 325 milliseconds.
- Enhanced mode throughput provides programmable scan times from 56 to 650 milliseconds.
- Select between 16-bit two's complement or offset binary unipolar data output.
TECHNICAL INFORMATION
Compatibility
- Compatible with Allen-Bradley 1794-TB2, 1794-TB3, and 1794-TB3T terminal bases.
- Supports 100, 200, and 500 ohm platinum RTD sensors.
- Supports 100, 120, 200, and 500 ohm nickel RTD sensors.
- Supports 10 ohm copper RTD sensors.
TECHNICAL RESOURCES
Documentation
COMPATIBILITY
Compatibility & Replacement
COMPATIBLE MODELSCompatible with Allen-Bradley 1794-TB2, 1794-TB3, and 1794-TB3T terminal bases. Supports 100, 200, and 500 ohm platinum RTD sensors. Supports 100, 120, 200, and 500 ohm nickel RTD sensors. Supports 10 ohm copper RTD sensors.
Verify compatibility against the exact Part Number, revision and manufacturer documentation before ordering.
PART VERIFICATION
Before You Order
Industrial automation parts can share similar model names, suffixes and revisions. Confirm the complete manufacturer Part Number before purchase.
01Check Part NumberMatch the complete ordering code on the existing unit.
02Confirm RevisionCheck suffix, hardware or firmware when applicable.
03Send a Label PhotoWe can review a clear label photo when identification is uncertain.
ORDERING PROCESS
From RFQ to Dispatch
1Submit Part Number2Verify Product Identity3Confirm Stock & Condition4Issue Quotation5Dispatch & Tracking
PRODUCT FAQ
Frequently Asked Questions
Which RTD sensor types can connect to the 1794-IR8 module?
The module supports Platinum, Nickel, and Copper RTD sensors within a 1 to 433 ohm range.
Which terminal bases are compatible with the 1794-IR8?
The unit installs onto Allen-Bradley 1794-TB2, 1794-TB3, and 1794-TB3T terminal base units.
What is the resolution of the 1794-IR8 analog input channels?
Each channel provides 16-bit resolution across an input span of 435 ohms.
