Rockwell Allen-Bradley 1794-IE8B Distributed Analog Input Module

This is a FLEX I/O distributed analog input module. 1794-IE8B = 1794-IE8 Series B. “B” denotes hardware series revision instead of part number suffix; it is commonly referred to as 1794-IE8B in the industry.

✅ Basic Information

Modelo: 1794-IE8 (Série B, commonly called 1794-IE8B)

Marca: Rockwell Allen-Bradley

Tipo: 8-channel single-ended non-isolated analog input module

Sistema: FLEX I/O distributed I/O, used with 1794 adaptadores (1794-AENT, 1794-ASB, etc.)

Matching Terminal Base: 1794-TB3 / TB3G terminal base (deve ser encomendado separadamente)

Vida útil: Active product, available for new purchase and repair, not discontinued

📋 Core Technical Specifications

Item	Parâmetro
Canais	8 single-ended analog inputs, non-isolated between channels
Signal Ranges (software configurable per channel)	4~20mA, 0~20mA, 0~10V, ±10V
Resolução	Unipolar: 12pedaço; Bipolar: 11pedaço + bit de sinal; Data format: 16-bit left-justified two’s complement
Tempo de conversão	Total conversion time for all channels: 256μs
Precisão	0.29% FS absolute full-scale accuracy at 25°C
Fonte de energia	24CCV (19.2~31,2 VCC), module current draw approx. 60mA @24VDC
Temperatura operacional	0°C ~ +55°C
Montagem	Trilho DIN, FLEX I/O local bus (Flexbus)
Programas	Estúdio5000 / RSLogix5000 configuration

🧩 Application Scenarios

FLEX I/O remote distributed analog acquisition: transmitters for pressure, temperatura, nível, flow with 4-20mA signal, 0-10V valve feedback. Widely used as remote I/O station for ControlLogix systems.

Observação: Sem isolamento galvânico entre canais. Large ground potential difference among multiple sensors will cause common-mode interference. External signal isolator is required.

🔌 LED Indicator Definition

Solid green: Module healthy, communication OK

Solid red: Module fault / configuration mismatch (electronic key error)

Flashing red: Communication loss with FLEX adapter

Desligado: No 24VDC power supply or hardware damage

⚠️ Common Troubleshooting Points

Verify correct base model, no bent bus pins; module must fully engage and lock into base latches
Confirm 24VDC supply voltage within 19.2~31.2V range
Studio5000 configuration: Exact Match electronic key recommended; each channel range must match field sensor
Signal fluctuation: Verifique o aterramento. For single-ended input, add isolator if ground offset exists
No reading: Inspect terminal wiring, distinguish current/voltage terminals; current loop must form closed circuit

📌 Alternative / Related Series Reference

Same family: 1794-IE8K (conformal coated version), 1794-IE8XT (wide-temperature XT version)

Alternativa doméstica: Distributed analog input module (must match remote bus protocol)

📦 HS Code Reference (Comércio Internacional)

85371011 (Programmable controller I/O module, subject to customs broker final confirmation)

1794-IE8A (Série A) vs 1794-IE8B (Série B)

Base part number remains 1794-IE8. A/B stand for hardware series revision, not separate part numbers. Aparência, base, fiação, faixa, resolution and accuracy are fully interchangeable for physical installation. Differences lie in power-up behavior before configuration, data word structure and explosion-proof certification.

Principais diferenças (Official Manual Highlights)

Item de comparação	1794‑IE8 Series A (Commonly called 1794‑IE8A)	1794‑IE8 Series B (Commonly called 1794‑IE8B)
Unconfigured Power-up Behavior (Mais crítico)	When module powers up before configuration download, channels return fixed false readings of approx. 2V or 4mA. PLC receives non-zero value which may trigger false interlock or alarm.	Novo “DESLIGADO” range added. Channels return 0V / 0mA before configuration, eliminating false analog readings for safer commissioning.
Data Word: Power-Up Status Bit	No such status bit	Input data word includes Power-Up bit. The bit is set once module power-up completes. Program can detect module startup to implement power-up masking logic.
Certificação à prova de explosão	No Zone2 certification	New IECEx / ATEX Zone2 certification: Ex ec IIC T4 Gc, suitable for Division 2 áreas perigosas
Hardware / Circuito	Legacy PCB with older components	PCB redesign, updated component bill of materials, fixes power-up reading drift issue of A-series
Software Configuration Compatibility	RSLogix5000 configured as Series A	Estúdio5000 / RSLogix5000 configured as Series B; backward compatible with A mode. B module can use A configuration directly to replace legacy A module.
Vida útil	Obsoleto, only second-hand/spare parts available	Ativo, new units available for purchase

Recursos comuns (Field Replacement Highlights)
Canais: 8-channel single-ended non-isolated analog input, ranges 4~20mA, 0~20mA, 0~10V, ±10V
Resolução, conversion speed, precisão, 24VDC supply and operating temperature range are identical
Compatible terminal bases: 1794-TB3 / TB3G, identical wiring diagram
Ônibus: FLEX I/O Flexbus, compatible with all FLEX adapters such as 1794-AENT, ASB

III. Engineering Replacement Considerations

A → B Replacement

Physical plug-and-play installation. Existing A-series configuration can be retained (B module supports A compatibility mode), or switch to B configuration to enable power-up status bit.

✅ Recommendation: Keep original configuration, no program modification required for direct replacement.

B → A Replacement

Physically installable. No entanto, A module returns false 4mA/2V readings when powered up without configuration. Take precautions for interlock to prevent equipment false action during commissioning or restart.

Electronic Key: If `Exact Match` strict matching is set in Studio5000, A and B revision mismatch triggers configuration fault. Switch to `Compatible Module` compatibility mode.
Recomendação de seleção

New projects and hazardous areas: Prefer 1794-IE8B for safe zero signal on power-up

Spare parts for legacy system: B can replace failed A module. If system is sensitive to analog signal transient at startup, implement power-up delay masking logic in PLC program.

Rockwell Allen-Bradley 1794-IE8B (1794-IE8 Series B) Especificações técnicas detalhadas

FLEX I/O 8-channel single-ended non-isolated analog input module

Informações Básicas

Modelo: 1794-IE8 Series B (Commonly called 1794-IE8B)

Marca: Rockwell Automation Allen-Bradley

Tipo: IA de entrada analógica, 8 single-ended inputs

Ônibus: FLEXBUS (FLEX I/O backplane local bus)

Matching Terminal Base: 1794-TB3 / 1794-TB3G (deve ser adquirido separadamente)

Supported Adapters: 1794-AENT, 1794-ASB, 1794-ADN and other FLEX I/O adapters

Supported Software: RSLogix5000 / Estúdio5000

Origem: Cingapura; Standard Warranty: 1 ano

Certificação à prova de explosão: IECEx / ATEX Ex ec IIC T4 Gc (Zone2) (Exclusive for B series, not available for A series)

Channel Electrical Specifications

Item	Parâmetro
Número de canais	8 canais, single-ended, no galvanic isolation between channels
Configurable Ranges (per-channel independent configuration)	4~20mA, 0~20mA, 0~10V, ±10V, OFF range (new for B series)
Resolução	Unipolar: 12 pedaço; Bipolar: 11 pedaço + bit de sinal
Formato de dados	16-bit left-justified two’s complement
Quantization LSB	Tensão: 2.56 mV/count; Atual: 5.13 μA/count
Total Conversion Time	Todos 8 channels total conversion: 256 μs
25°C Full Scale Absolute Accuracy	0.29% FS (tensão e corrente)
Full Temperature Range Accuracy (0~55°C)	0.5% FS
Common Mode Voltage	±50V (common-mode rejection only, not galvanic isolation)
CMRR (Common Mode Rejection Ratio)	≥60dB @50/60Hz, source impedance 249Ω
NMRR (Normal Mode Rejection Ratio)	≥40dB @50/60Hz
Impedância de entrada	Modo de tensão: >1MΩ; Modo atual: 250Oh
Unconfigured Power-up State	B-series: channels return 0mA/0V; built-in Power-Up status bit

III. Especificações da fonte de alimentação

Item	Parâmetro
External Module 24V DC Supply	19.2 ~ 31.2 CCV, nominal 24VDC
Module Power Consumption Current	60mA @24VDC
Backplane 5V FLEXBUS Current	Typical 30mA (supplied by FLEX adapter)
Field Loop Current	Current transmitter loop powered by external 24V supply, module only samples signal

Ambiental & Especificações Mecânicas

Item	Parâmetro
Temperatura operacional	0°C ~ +55°C (32℉ ~ 131℉)
Temperatura de armazenamento	-40°C ~ +85°C
Umidade relativa	5%~95%, sem condensação
Vibração	IEC60068‑2‑6, 10~150Hz, 1g
Choque	IEC60068‑2‑27, 30g peak
Método de montagem	Montagem em trilho DIN, stacked on FLEX I/O base
Proteção de entrada	IP20 (module body, installed inside control cabinet)
EMC	Compatível com EN 61006 industrial immunity standard

Indicadores LED de status

Solid green: Module healthy, comunicação / configuration OK

Solid red: Falha de hardware / electronic key mismatch, erro de configuração

Flashing red: FLEXBUS communication interrupted, lost connection with adapter

Desligado: Loss of 24V supply or backplane power

Estrutura de dados (B-Series Exclusive)
Input data area: 16-bit raw analog count values for 8 canais
Power-Up status bit (new for B series): Bit is set once module power-up completes. PLC program can read it to mask signals during startup and prevent interlock false action
Configuration word: Individual channel range selection, supports OFF range to force zero signal when unconfigured

VII. Limitações Críticas (Engineering Focus)

No channel isolation: Single-ended input. External signal isolator is mandatory when large ground potential difference exists among field sensors, otherwise drift and signal jitter will occur
Current input: Internal 250Ω sampling resistor inside module; transmitter loop must form closed circuit
Electronic Key: Studio5000 configuration, Exact Match for strict revision check. A/B revision mismatch triggers fault under strict mode; switch to Compatible Module for replacement

VIII. Related Derivative Models

1794-IE8K: Conformal coated version

1794-IE8XT: Wide temperature XT version, operating temperature -40~70℃

1794-IE8A: Legacy A version, no Zone2 explosion-proof rating, no zero signal on power-up, no Power-Up bit

Referência do Código HS (Customs Declaration)

85371011, Programmable Controller I/O Module (final confirmation required from customs broker)

Rockwell 1794-IE8B Installation Method (FLEX I/O)

Separated structure: Terminal base (1794-TB3 / TB3G) mounts on DIN rail first, then plug 1794-IE8B module onto base. Module body cannot be fastened directly onto rail.

Mounting Carrier
Rail Specification: Standard 35×7.5mm EN50022 DIN rail (AB part 199-DR1). Horizontal mounting inside cabinet preferred. Add rail stop 1492-EA35 for anti-vibration if vertically mounted
Alternativa: Panel Screw Mount: Base has mounting holes for direct screw fastening on cabinet backplate (not recommended for high vibration applications)
Matching Base: Must use 1794-TB3 / 1794-TB3G. TB3G is spring-cage tool-free terminal. Base integrates Flexbus internal bus connector for daisy-chaining adjacent adapters/bases
Complete Installation Procedure (Official Standard Process)

⚠️ Critical Safety Rule: Base removal is prohibited under power; module hot-swap is electrically allowed but not recommended for frequent field operation

Step1: Mount Terminal Base onto DIN Rail

Hook upper latch of base onto DIN rail, press down base until latch clicks and locks
Daisy-chain multiple bases/adapters: Fully retract Flexbus connector inside base first, push base tightly against left adapter/base, then push Flexbus connector leftward and insert into adjacent unit to complete FLEXBUS backplane connection
Set base model key switch: Posição 3 for 1794-IE8 (small rotary switch on base side; wrong setting leads to module identification failure)
Install end stops on both rail ends to prevent base sliding

Step2: Install 1794-IE8B Electronic Module

Inspect bottom gold fingers of module for bending or damage
Align upper module guide rib with base guide slot, align vertically to base
Press module down evenly until both side latches of base automatically lock (audible click), module fits flush against base

Do not apply excessive force, risk bending 16-pin bottom bus pins

Step3: Fiação Terminal

Row C terminals of base: 24Potência VCC; Row B: 24V common and channel ground; Row A: 8-channel analog signal inputs
Shielded twisted pair recommended for analog signal cable, shield single-point grounded; current signal loop must be closed
Close terminal protective cover after wiring completion

Step4: Pre-Power-up Inspection

Base key switch set to 3
All Flexbus connectors fully engaged, no gaps between bases
Travas do módulo totalmente travadas
24V supply voltage: 19.2~31,2 VCC
Verify signal cable free of short circuit and misconnection

III. Ambiente de instalação & Layout Requirements

Local de montagem: IP20 inside control cabinet, keep away from strong interference and heat sources such as VFDs, contactors and transformers
Dissipação de calor: Reserve ventilation gap above and below module; operating temperature range 0~55℃
Aterramento: Use galvanized steel DIN rail with reliable protective earth connection; aluminum rail not recommended for poor grounding performance
Vibration application: Horizontal mounting optimal; rail locking components required for vertical installation
Procedimento de remoção
Disconnect field 24V signal circuit (recomendado)
Press both side release latches of base, lift 1794-IE8B module upward for removal (base remains on DIN rail)
To remove base: Retract Flexbus connector first, pry bottom DIN latch with flat screwdriver then lift base upward
Common Installation Errors
Base key switch not set to 3 → Module faults on power-up, cannot be recognized by configuration
Flexbus connector not pushed out or incomplete engagement → FLEXBUS communication loss, module red flashing
Module not fully seated, latches unlocked → Intermittent communication under vibration
Gaps between bases, floating bus connector → Unstable communication
High power cables and signal cables routed in same trunk → Analog signal drift and fluctuation
Installation Quick Notes