Overview
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | NFAI835-S50 |
| Brand | Yokogawa |
| Product Type | Analog I/O Module, 4-channel input and 4-channel output isolated channels |
| Origin | Japan |
| Weight | 0.3 kg |
| Power Consumption | 360 mA at 5 VDC; 450 mA at 24 VDC |
| Input Signal | 4-20 mA current input |
| Output Signal | 4-20 mA current output |
| Number of Channels | 4 input channels and 4 output channels |
| Channel Isolation | Isolation between input/output signals, system interface, and individual channels |
| Input Resistance | 25 ohm |
| Allowable Load Resistance | 0 to 750 ohm |
| Circuit Open Detection | 0.65 mA or less |
| Input Accuracy | +/-0.1% of full scale |
| Output Accuracy | +/-0.3% of full scale |
| Data Refresh Cycle | 100 ms |
| Input Step Response Time | 100 ms |
| Output Step Response Time | 100 ms |
| Output Failback | Configurable for each channel |
| Transmitter Power Supply | 20.2 to 29.3 VDC |
| Temperature Drift | Max. +/-0.01%/deg C |
| External Connection | Pressure clamp terminal block or MIL connector cable |
| HART Communication | Available with H suffix option |
4-20 mA Process Signal Isolation and HART Interface
Yokogawa NFAI835-S50 applies isolated analog signal processing for process instrumentation loops. The module separates field current signals from the control system side and provides channel-to-channel isolation for analog measurement and output circuits.
The module supports 4-20 mA HART loop protocol communication when configured with the HART communication option. Therefore, field transmitters can maintain digital communication capability while the module handles standard analog current transmission.
The isolated architecture reduces signal interaction between channels and supports stable analog acquisition in Yokogawa control environments. The module also provides transmitter power supply output from 20.2 to 29.3 VDC for connected field devices.
Frequently Asked Questions
Q: Does the NFAI835-S50 support both analog input and analog output functions?
A: Yes. The module provides four isolated 4-20 mA input channels and four isolated 4-20 mA output channels in the same hardware unit.
Q: What isolation functions does the NFAI835-S50 provide?
A: The module isolates input/output signals from the system interface and isolates individual channels to reduce electrical interference between circuits.
Q: Can the NFAI835-S50 communicate with HART field devices?
A: Yes. HART communication is available when the module uses the HART communication suffix option.
Field Installation Guidelines
- Install the NFAI835-S50 according to Yokogawa FA-M3 or compatible system hardware installation procedures.
- Connect 4-20 mA field wiring using suitable shielded instrumentation cables when operating in electrically noisy environments.
- Ground cable shields according to the control system grounding design to reduce electromagnetic interference.
- Separate analog signal cables from high-voltage power wiring and switching circuits.
- Verify current loop polarity before energizing the module.
- Confirm transmitter power supply wiring before connecting external field devices.
- Use the specified terminal block or MIL connector cable according to the selected option code.
- Check channel configuration and output failback settings before commissioning.
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