Valmet Automation AIU16T Analog Input Module – 16‑Channel (65421466‑2B MT924 V1.3)

The Valmet Automation AIU16T is a high‑density analog input module designed for the Valmet DNA and Metso distributed control systems. With 16 universal channels, it can accept 4‑20 mA, 0‑20 mA, 0‑10 V, or thermocouple signals, making it an extremely flexible front‑end for process measurement. The version 1.3 (MT924) and order code 65421466‑2B feature improved noise rejection and extended diagnostics over earlier releases.

Channel Configuration and Signal Range

Each of the 16 inputs can be individually programmed via software to accept current (0‑20 mA, 4‑20 mA), voltage (0‑5 V, 0‑10 V, ±10 V), or thermocouple types (J, K, T, E, N). The module uses a 16‑bit ADC with an oversampling rate of 256 to provide effective resolution of 15 bits. The input impedance is 250 Ω for current mode and >1 MΩ for voltage mode. A built‑in current loop supply (24 V) is available for powering two‑wire transmitters on up to 8 channels simultaneously.

Accuracy and Performance

The AIU16T achieves an accuracy of ±0.05 % of full scale at 25 °C, with a temperature coefficient of ±25 ppm/°C. The update rate per channel is configurable from 10 ms to 1 s, with a typical scan time of 100 ms for all 16 channels. The module features a digital filter that can be set to 50 Hz or 60 Hz rejection to eliminate power‑line noise. A self‑calibration routine runs automatically every 24 hours to compensate for drift.

Galvanic Isolation and Protection

All channels are isolated from the system bus and from each other by a 1000 V DC barrier. Each input includes over‑voltage protection up to 30 V DC and reverse‑voltage protection. The module can withstand ESD discharges up to 8 kV per IEC 61000‑4‑2. In case of a channel overrange, the ADC clips safely and an overrange flag is set in the status register without affecting other channels.

Communication and Data Format

Data exchange with the host controller occurs via the Valmet I/O bus (a proprietary CAN‑based protocol). The module supports cyclic transfer of raw ADC values, scaled engineering units, and channel status bytes. It also provides a diagnostic data record containing supply voltage, internal temperature, and communication error counters. The module can be configured using the Valmet Engineering Tool, and a downloadable EDS file simplifies integration with third‑party systems.

Hardware and Mounting

The AIU16T is a 6U x 4HP module (233 mm x 20 mm) that fits into standard Valmet subracks. The front panel features 16 LED indicators that glow green for normal operation, yellow for alarm, and red for fault. The field wiring is terminated via a 50‑pin female connector that mates with a pre‑wired cable harness. The module draws 350 mA from the 5 V rail and 50 mA from the 24 V rail (excluding loop power).

Environmental Conditions

Operating temperature: 0 °C to 55 °C; humidity: 10‑90 % non‑condensing. The board is coated with a protective conformal layer to resist chemical attack. It meets EN 61326‑1 class A emissions and immunity standards. MTBF is calculated at 750,000 hours at 40 °C.

Applications

This module is extensively used in boiler control, where it monitors feedwater flow, drum level, and flue gas oxygen. In pulp mills, it reads consistency, pH, and temperature sensors. Its high channel count reduces the number of modules required, saving rack space and cost.

Maintenance and Diagnostics

Routine maintenance involves checking terminal connections and verifying calibration with a process calibrator. The module logs open‑circuit and short‑circuit events for each channel; these logs can be accessed through the diagnostic interface. Firmware updates are performed via the backplane using the system loader, without removing the module.

Conclusion

The Valmet Automation AIU16T analog input module (65421466‑2B MT924 V1.3) provides a cost‑effective, high‑performance solution for measuring a wide range of process signals. Its flexibility and reliability make it an integral part of modern control systems.