Description
Metso AAI835-H50
Technical Specifications 4 analog input channels plus 4 analog output channels; signal range 4 to 20mA for both input and output; each channel provides full galvanic isolation; isolation withstand voltage 500V AC between channels and between field side and system side; allowable input current up to 25mA; transmitter supply voltage ranges 15V minimum at 20mA and 29.3V maximum at 0mA; input measurement accuracy ±16μA; output regulation accuracy ±48μA; HART protocol support; module weight 0.2kg.
Functional Features Receives analog process measurement signals from pressure, flow and level transmitters on input channels. Generates analog control output signals to regulate control valves and field actuators on output channels. Supports HART digital communication for reading smart instrument secondary values and diagnostic faults. Implements open-circuit detection on input loops when current falls below 0.65mA. Uploads channel fault status, communication quality and process values to the Metso DCS controller. Supports fail-safe output state configuration when rack communication is lost.
Application Scenarios Mining mineral processing control loops, pulp mill digester and bleaching process control, paper machine auxiliary regulation loops, slurry pipeline flow control, industrial wastewater closed-loop control.
Performance Parameters High channel isolation resistance to reduce crosstalk; fast analog output response for PID regulatory loops; low output drift under continuous load; accurate open-loop fault identification for field instrument wiring.
Material Composition Internal circuit board uses FR-4 high-reliability flame-retardant multilayer PCB; analog conversion and output drive chips are precision industrial semiconductors; isolation devices are optocoupler isolation amplifiers; backplane gold finger contacts are gold-plated copper alloy; module housing is flame-retardant thermoplastic material; terminal contact components are nickel-plated copper.
Structural Characteristics Standard rack plug-in card for Metso DNA control racks. Front panel contains power LED, bus communication LED and individual channel fault indicators. Rear gold finger connector mates with rack backplane for power and system bus connection. Mechanical locking clip fixes the card in the rack slot. Field wiring connects through matched terminal base assemblies.
Working Principle Input side 4-20mA field signals pass through isolation and filtering circuits before analog-to-digital conversion. Digital measurement data is sent to the DCS controller through the rack backplane bus. The controller sends control setpoint values back to the module. The module’s digital-to-analog converters generate conditioned 4-20mA output signals to drive field actuators. HART modulation and demodulation circuits overlay digital data onto the analog current loop for smart device access.
Installation Requirements Cut off rack power before module installation or removal. Insert the module into the specified rack slot and lock the retaining clip. Connect field transmitters and valve positioners to the corresponding terminal base using shielded twisted pair cables. Configure signal ranges, output fail-safe states and HART parameters in Metso DCS engineering software. Perform channel calibration before process commissioning.
Precautions for Use Match output channel load impedance with module output drive capacity. Avoid running analog instrument cables alongside variable frequency drive power cables. Verify HART multi-drop wiring rules when multiple smart instruments share one loop. Test fail-safe output behavior during system outage simulation.
