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A guide to diagnosing and resolving common issues with ROSSMA IIoT-AMS devices.
Possible causes:
- Battery discharged
- No LoRaWAN/NB-IoT coverage
- Incorrect activation settings (ABP/OTAA)
- Signal shielding (metal enclosure, basement)
- Device not registered on the server
Solution:
- Check battery voltage via the ROSSMA NETS server (should be >3.0 V)
- Check the signal level RSSI (should be > -120 dBm)
- Ensure that activation keys are entered correctly
- Move the device closer to a window or base station
- Verify device registration in ROSSMA NETS
Possible causes:
- No 220 V power at the L/N terminals
- Built-in fuse has blown
- Incorrect phase and neutral connection
Solution:
- Check for 220 V with a multimeter
- Check the condition of the input circuit breaker
- Ensure correct L and N connections
- Contact the ROSSMA service center
Possible causes:
- Too frequent communication intervals
- Transmitter power too high
- Poor network coverage (device spends energy on retransmissions)
- Faulty sensor or input
Solution:
- Increase the data transmission interval (recommended: no more than once per hour)
- Reduce transmitter power in settings (if coverage is adequate)
- Improve reception conditions or use a repeater
- Check the connected sensors for faults
Reference: Estimated battery life — up to 10 years with 1 transmission per day. See Battery Replacement for lifespan tables.
Normal operation (autonomous devices):
- LED blinks during communication (at the configured interval)
- ACT LED blinks when data is received from sensors
Problems:
- Both LEDs are off — power issue (battery discharged or disconnected)
- Communication LED does not blink for an extended period — no network connection
- Error LED blinks once per second — communication module not detected
- Error LED blinks 3 times – pause – 3 times — device cannot register on the network
- Error LED blinks 5 times – pause – 5 times — data transmission error
Possible causes:
- Incorrect connection polarity
- Break in the data line (DQ)
- Faulty or incompatible sensor
- Missing pull-up resistor (for multiple sensors)
Solution:
- Check polarity: GND to GND, DQ to DQ, VDD to VCC
- Check wire continuity with a multimeter
- Replace with a known working sensor
- Install a 4.7 kΩ resistor between DQ and VCC
Possible causes:
- Sensor installed in a location with poor heat exchange
- Sensor near a heat source
- Incorrect sensor calibration
- Sensor damaged
Solution:
- Move the sensor to a location with better heat exchange
- Isolate the sensor from direct sunlight and heat sources
- Test the sensor in a glass of ice water (should read ~0°C)
- Replace the sensor if readings are incorrect
Possible causes:
- Missing 4.7 kΩ pull-up resistor
- Address conflict (ROM collision)
- Maximum bus length exceeded
- Too many sensors on one line
Solution:
- Install a 4.7 kΩ resistor between DQ and VCC
- Use quality cable (twisted pair)
- Reduce line length (max 100 m)
- Reduce the number of sensors (recommended up to 10)
Possible causes:
- Incorrect connection
- Faulty input
- Incompatible signal type
Solution:
- Check the wiring diagram and polarity
- Ensure the signal matches the input type
- Contact the ROSSMA service center
Possible causes:
- Signal frequency too high
- Contact bounce
Solution:
- Ensure the frequency does not exceed 300 Hz or use a divider
- Use a counter with debounce protection or add an RC circuit
Possible causes:
- Interference on the line
- Noise from power cables
Solution:
- Check cable shielding, use twisted pair
- Use galvanically isolated inputs
- Route signal cables separately from power cables
Possible causes:
- No response from Modbus devices (incorrect Slave ID)
- Connection error A+/B- (polarity reversed)
- Incorrect baud rate
- Break in the RS-485 line
- Parity settings mismatch
Solution:
- Verify the Slave ID in the configurator
- Check A+/B- polarity with a multimeter (A+ should be 1-2 V higher than B- in idle state)
- Ensure the baud rate matches the connected devices
- Check RS-485 cable integrity
- Use a Modbus scanner for device diagnostics
- Measure resistance between A+ and B- — should be 120 Ω (with terminators installed)
Possible causes:
- Incorrect Slave ID configuration
- Different baud rates
- No power to the Modbus device
- RS-485 line length exceeded
Solution:
- Use a USB-RS485 adapter and Modbus Poll software to test the device
- Ensure the device Slave ID matches the configuration
- Verify that the baud rate is the same (typically 9600 or 19200)
- Measure line resistance
- Add 120 Ω terminators at both ends of the line
Possible causes:
- Wrong data type in the profile (Float instead of Uint16)
- Wrong byte order (Big Endian / Little Endian)
- Incorrect register address
- Scale factor needs to be applied
Solution:
- Study the Modbus device documentation (register map)
- Ensure the data type in the profile matches the device
- Check byte order (ABCD, BADC, CDAB, DCBA)
- Verify scale factors
- Use the Data Decoder to analyze the payload
Solution:
- Ensure the RS-485 interface is activated (see the meter's datasheet)
- Check the network address (factory default — usually 1 or 0)
- Baud rate should be 9600, parity — Even
- Use the Mercury Configurator software to test communication
Solution:
- Verify the meter supports the Modbus RTU protocol
- Default network address — 1
- Baud rate — 9600, parity — Even
- Ensure the correct register map is used (see the datasheet)
Solution:
- Verify the heat calculator is powered on and operational
- Default address — 1, baud rate — 9600, parity — None
- Ensure firmware with Modbus RTU support is installed
- Use the SPT Configurator software to test communication
Solution:
- Default address — 247 (must be changed via the device menu)
- Baud rate — 9600, parity — Even
- Activate Modbus RTU mode via the device menu (see the manual)
Possible causes:
- No communication with the server (device not receiving the command)
- Faulty relay
- Not registered on the server
Solution:
- Verify the device is registered on the ROSSMA NETS server
- Check the LoRaWAN/NB-IoT signal level (RSSI should be > -120 dBm)
- Send an on/off command via the web interface
- If the relay does not click, contact the service center
Possible causes:
- Break in the load circuit
- Incorrect load connection (wires on wrong terminals)
- Load fuse blown
- Load is faulty
Solution:
- Disconnect 230 V power
- Verify correct load connection to COM and NO terminals
- Check the load wiring integrity
- Check the load itself (lamp, pump, etc.) — it must be functional
- Measure resistance between COM and NO with the relay energized (should be ~0 Ω)
Solution for IN1, IN2 (galvanically isolated):
- Check connection polarity: IN1+ to positive, IN1- to negative
- Check wire integrity
- Measure voltage between IN1+ and IN1- (should be 0 V when the contact is open)
Solution for IN3, IN4:
- Verify one wire is connected to IN3/IN4, the other to GND
- Manually short IN3 to GND — the status should change on the server
- Check the sensor contact integrity
Possible causes:
- Rated current exceeded (>10 A)
- Short circuit in the load
- Inductive load without a snubber (contact arcing)
Solution:
- Measure the load current with clamp meter (should be <10 A)
- If current >10 A, use an intermediate contactor
- For inductive loads (motors), install an RC snubber:
- Resistor 47–100 Ω, 2 W
- Capacitor 0.1–0.47 µF, 400 V
- Connect in parallel with the contactor coil or motor
For issues not described above, contact ROSSMA technical support:
Before contacting support, prepare: device serial number, problem description, server data screenshots, connection photos (if applicable).
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