AAI841-S50/K4A00

The Yokogawa AAI841-S50/K4A00 is a non-isolated analog I/O module designed for 4-20 mA signal processing in Yokogawa distributed control systems. It provides 8 analog input channels and 8 analog output channels, allowing field measurement signals to be transferred to the control system and controller output signals to be delivered to field devices. The specified configuration includes a KS Cable Interface Adapter.

Functional Description

The AAI841 handles both analog input and output signals within one module. Its eight input channels receive 4-20 mA signals from field transmitters, while its eight output channels provide 4-20 mA signals for control devices such as valve positioners and other current-operated equipment.

The module converts incoming analog signals into internal control-system data and converts output data from the field control station into corresponding analog current signals. This supports measurement and control functions through a shared I/O module.

Signal and Channel Configuration

The module supports up to eight analog input/output loops. Each input channel accepts a 4-20 mA DC signal, with an allowable input current of 25 mA. Each output channel supplies a 4-20 mA signal and supports a connected load resistance of 0 to 750 ohms.

The input and output circuits are non-isolated. This distinction is important when checking field wiring, grounding arrangements and potential differences between connected devices. The module should not be treated as an isolated I/O solution.

Response and Accuracy

The input data update period is 10 ms, with an input step response time of 100 ms. The output step response time is 40 ms. These values describe different stages of signal processing and should be considered separately when evaluating control-loop response requirements.

The specified input accuracy is +/-16 uA, while output accuracy is +/-48 uA. Output circuit-open detection operates below 0.65 mA, providing a means of identifying an open output circuit.

Transmitter and Output Requirements

The AAI841 supports channel-level selection for 2-wire or 4-wire transmitter connections through setting pins. For 2-wire transmitters, the specified transmitter supply voltage is at least 14.8 V at 20 mA and no more than 26.4 V at 0 mA. External wiring voltage drop must be considered when checking the transmitter's minimum operating voltage.

The output load resistance must remain within the specified 0 to 750 ohm range. This value should be checked against the total connected load, including relevant wiring resistance.

Model and Ordering Configuration

The complete ordering code identifies the module's standard configuration and cable interface option:

• -S: Standard type, without the HART communication designation.
• 5: Configuration without explosion protection.
• 0: Basic type.
• /K4A00: KS Cable Interface Adapter, model ATK4A-00.

The /K4A00 option identifies the specified cable interface adapter. It should be distinguished from the module's signal-processing function when checking replacement and connection requirements.

Technical Specifications

Parameter	Specification
Model	AAI841-S50/K4A00
Brand	Yokogawa
Product Type	Analog I/O Module
Input Channels	8
Output Channels	8
Input Signal	4-20 mA DC
Output Signal	4-20 mA DC
Channel Isolation	Non-isolated
Allowable Input Current	25 mA
Input Accuracy	+/-16 uA
Output Accuracy	+/-48 uA
Input Resistance	400 ohms at 20 mA to 1000 ohms at 4 mA
Output Load Resistance	0 to 750 ohms
Circuit-Open Detection	Less than 0.65 mA
Data Update Period	10 ms
Input Step Response Time	100 ms
Output Step Response Time	40 ms
Temperature Drift	+/-0.1%/10 deg C
Transmitter Supply Voltage	14.8 V minimum at 20 mA; 26.4 V maximum at 0 mA
Transmitter Configuration	2-wire or 4-wire, selectable per channel
Maximum Current Consumption	310 mA (5 V DC); 500 mA (24 V DC)
Connection Option	KS Cable Interface Adapter ATK4A-00
Weight	0.3 kg

Frequently Asked Questions

Q: How many field signals can the AAI841-S50/K4A00 handle?

A: It supports eight analog input channels and eight analog output channels, with both directions using 4-20 mA signals. The configuration supports up to eight input/output loops.

Q: Does the AAI841-S50/K4A00 support HART communication?

A: The -S suffix identifies the standard type rather than the -H HART communication type. HART capability should not be assumed for this particular ordering code.

Q: Can this module be connected directly to a Zener barrier?

A: No. Yokogawa specifies that a Zener barrier must not be connected to this non-isolated module. For intrinsically safe applications, an isolation barrier is required.

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