Metso DNA system troubleshooting

Check connectors and cables: RVT/TT-125 uses MIL-C-5015 three core connectors, and common faults are pin corrosion or solder joint breakage. Re tighten the connector and replace the prefabricated cable if necessary. For long-distance transmission, ensure that the cable shielding layer is grounded at a single point on the I/O side.

Temperature output verification: Measure the DC voltage between pins C and B, which should be 10 mV/° C (0 ° C corresponds to 0 V? The actual sensor provides a range of 2~120 ° C, for example, about 200 mV at 20 ° C? Note that the specification sheet states "10 mV/° C" and the measurement range is+2~+120 ° C, so it should be around 250 mV at room temperature of 25 ° C. If the reading deviates significantly, a resistance box can be used to simulate temperature signals (requiring additional pull-up circuits) to determine whether it is a sensor or I/O channel issue.

Solution: If the sensor is confirmed to be damaged, replace it with the same model (RVT/TT-125, code 600-10026), and tighten the M8 bolts with a torque of 6 N · m during installation to avoid damaging the ceramic shear element due to over tightening. After replacement, the range needs to be re normalized in the channel corresponding to AIF8V (0~24 V corresponds to engineering units of g and ° C).

4.2 AIF8V/AIF8T units cannot be read or channel data is abnormal

Phenomenon: In the I/O diagnostic graph of DNA Operate, the AIF8V unit displays a red fault or a fixed channel value of -9999 (bad value). For AIF8T, the measured speed value is always zero.

Troubleshooting steps:

Utilizing hot plug recovery: ACN I/O M120 supports true hot plug. If a single channel fails, you can try unplugging the I/O unit and waiting for 10 seconds before reinserting it. The system will automatically reinitialize and restore communication. Attention: Before unplugging, it is necessary to confirm that the channel is not used for safety interlocking.

Check channel diagnostic information: Open the ACN I/O diagnostic interface in DNA Operate (see "ACN I/O diagnostics picture" on page 20 of the PDF). Each channel provides detailed diagnosis, including overload, disconnection, common mode voltage exceeding, etc. For AIF8V, the common diagnosis is "loss of on-site power supply" or "low load of constant current source".

Measure input impedance: The input impedance of AIF8V is 100 k Ω (voltage measurement mode). If the internal resistance of the on-site sensor or transmitter is too high, it will cause voltage division error. Disconnect the external wiring and use a multimeter to measure the resistance between terminal IN and COM, which should be around 100 k Ω. If it is close to 0, it indicates that the input circuit protection device has broken down; If it is infinitely large, it may be due to an open circuit in the sampling resistor.

AIF8T speed triggering issue: AIF8T is designed for synchronous sensors such as RTS-226, with an input impedance of 249 Ω and a channel specific current limiting power supply (30 mA). Use an oscilloscope to measure the trigger signal (which should be a square wave or sine wave with an amplitude of at least 5 Vpp). If there is no signal, check if the sensor is aligned with the gear or reflective tape; If there is a signal but it cannot be collected, try to adjust the trigger level and hysteresis value in the configuration of AIF8T. Additionally, please note that the measurement interval for AIF8T is 50 μ s (equivalent to a 20 kHz sampling rate), and longer acquisition times may be required for extremely low speeds (<1 Hz).

Check isolation performance: AIF8V and AIF8T channels are not isolated (shared COM), but 1500 VAC is isolated between channels and the system. If there is ground loop interference on site, the sensor shielding layer can be directly connected to the COM terminal, while ensuring that the COM is not connected to other ground on the I/O cabinet side.

Solution: If the diagnosis confirms a hardware failure of the unit, replace AIF8V (D201509) or AIF8T (D201510) with spare parts. After replacement, I/O addresses and range normalization parameters need to be reassigned in the Function Block CAD engineering tool (see "Analog RF and low pass filtering" settings on page 21 of the PDF). Attention: AIF8V supports two ranges of 0~24 VDC and -5~+5 VAC, which need to be selected through programming.

4.3 ACN MR Controller Redundancy Switching Failure or Startup Stuck

Phenomenon: After the main controller fails, the backup controller cannot take over, or when the controller is powered on, the PWR LED flashes but the STATUS LED remains red, and the node is not visible in the Metso DNA network.

Troubleshooting steps:

Check redundancy configuration: ACN MR supports 1:1 redundancy, requiring two controllers to be interconnected through dedicated Gigabit Ethernet ports (1000Base-T) and installed with the same SD card and real-time operating system version. Check the redundancy group settings in DNA Engineering Server and confirm that 'Redundancy pair' is enabled.

SD card swap test: All startup parameters of ACN MR (including RTOS, Process Controller software, and applications) are loaded by default from the backup server; In independent operation mode, it is loaded from the local SD card. If the main controller cannot start, you can unplug the SD card of the main controller and insert it into the backup controller to see if it can start normally. If possible, the original controller hardware is faulty (such as processor or memory); If not, the SD card is damaged or the file system is incorrect. Attention: After replacing the SD card, it is necessary to use Metso DNA engineering tool to re burn the image. Copying files alone is not effective.