AAI835-H03

The Yokogawa AAI835-H03 is an isolated analog input/output module designed for the CENTUM VP field control system. It provides four 4-20 mA analog input channels and four 4-20 mA analog output channels in one module. The HART communication function supports digital communication with compatible field instruments alongside analog signal transmission, allowing the control system to access both process measurements and instrument data.

Functional Description

The AAI835-H03 handles bidirectional analog signal conversion between field instruments and the Field Control Station (FCS). Input channels receive 4-20 mA signals from transmitters and convert them into digital process data for control and monitoring. Output channels convert FCS output data into 4-20 mA signals for positioning devices and other analog-controlled equipment.

All eight channels are isolated. This arrangement separates individual field signal circuits and helps limit interference caused by differences in field-side electrical potentials.

HART Communication

The HART version supports digital communication over compatible 4-20 mA instrument loops. The FCS can access analog process values and available HART variables through the I/O communication structure. This allows smart transmitter information to be handled alongside conventional analog process signals.

Technical Specifications

Parameter	Specification
Model	AAI835-H03
Brand	Yokogawa
Module Type	Analog I/O Module
Input Channels	4
Output Channels	4
Input Signal	4-20 mA DC
Output Signal	4-20 mA DC
Channel Isolation	Isolated between channels and between field and system
Allowable Input Current	25 mA
Input Resistance	290 to 450 ohm (at 4 to 20 mA)
Allowable Output Load	0 to 750 ohm
Input Accuracy	+/-16 uA
Output Accuracy	+/-48 uA
Data Update Period	10 ms
Transmitter Power Supply	15.0 V or higher at 20 mA; 29.3 V or less at 0 mA
Temperature Drift	+/-16 uA/10 deg C
Maximum Current Consumption	360 mA at 5 VDC; 450 mA at 24 VDC
HART Communication	Supported
Withstanding Voltage	500 VAC for 1 minute
External Connection	Pressure clamp terminal, MIL connector cable, dedicated KS1 cable
Weight	0.30 kg
Temperature Option	-20 to 70 deg C
Corrosion Protection	ISA Standard G3

Signal Processing and Electrical Characteristics

The four input channels accept current signals from 2-wire or 4-wire transmitters. Transmitter configuration is selected individually for each channel using the module setting pins. The built-in transmitter supply supports loop-powered instruments, with external wiring voltage drops needing consideration when checking the minimum operating voltage.

The four output channels supply current signals to field control devices. The specified output load range of 0 to 750 ohm defines the permissible connected load resistance. Circuit-open detection is provided when the output current falls below 0.65 mA.

Installation and Connection Considerations

The module supports pressure clamp terminals, MIL connector cables and dedicated KS1 cables for external signal connections. The selected connection method determines the appropriate terminal or cable arrangement.

For intrinsically safe applications, Yokogawa specifies that a Zener barrier must not be connected to this module. An isolation barrier should be used instead. The specified isolation withstand voltage also depends on the external cable configuration.

Frequently Asked Questions

Q: How many field instruments can the AAI835-H03 connect to?

A: The module provides four analog input channels and four analog output channels. It can therefore handle four input signals and four output signals simultaneously.

Q: Does the AAI835-H03 support HART instruments?

A: Yes. Its HART communication function supports digital communication with compatible field instruments over the analog current loops, allowing access to available instrument data in addition to the 4-20 mA process signals.

Q: What should be checked when replacing an existing AAI835 module?

A: Verify the complete model suffix, HART communication requirement, environmental option, external connection method and terminal arrangement. The replacement must also match the applicable FIO system configuration.

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