How to configure 5 RS485 Ultrasonic Fuel Sensors with FMC125?

Telematics Question
1

Hello,

I am looking for detailed instructions on how to connect and configure 5 ultrasonic fuel sensors to a single FMC125 tracker using the RS485 interface.

Please note that the standard Wiki article for the UL202 sensor (available at https://wiki.teltonika-gps.com/view/UL202_Ultrasonic_Fuel_Sensor) does not answer this question, as it only covers the basic integration of a single sensor and does not explain how to handle multiple sensors on the same RS485 bus.

Specifically, I need guidance on the following points:

  1. Physical Wiring / Daisy-Chaining: Are there specific recommendations for wiring 5 sensors in parallel (daisy-chain) on the FMC125’s RS485 A and B lines? Do I need to add a termination resistor ($120\ \Omega$) at the end of the chain?

  2. Sensor Addressing: How should the Modbus / LLS network ID/address be configured on each of the 5 ultrasonic sensors to prevent collisions?

  3. Teltonika Configurator Settings:

    • Which RS485 mode should be selected in the FMC125 configuration (e.g., LLS, Modbus, or TCP Binary)?

    • How do I map each of the 5 sensors to the corresponding I/O elements (such as LLS 1 to LLS 5 Fuel Level / Temperature) so that all 5 measurements are sent independently to the server?

  4. Firmware Version: Is there a specific firmware version required to support up to 5 sensors on RS485 for this model?

Any step-by-step guide, wiring diagram, or configuration screenshot for this multi-sensor setup would be highly appreciated.

Thank you in advance for your help!

Best regards,

2

Hi,

Thanks for writing to us.

You cannot connect 5 ultrasonic sensors via RS485. Ultrasonic sensors are supported only via RS232 (one per port). If you need 5 fuel sensors on a single FMC125, use LLS-type sensors on the RS485 bus in a daisy-chain configuration.

For using RS485 UL sensor but we can connect multiple LLS sensors in parallel in daisy chain.

RS485 A (+) → Sensor 1 A → Sensor 2 A → Sensor 3 A → Sensor 4 A → Sensor 5 A
RS485 B (−) → Sensor 1 B → Sensor 2 B → Sensor 3 B → Sensor 4 B → Sensor 5 B
GND → Common ground to all sensors
Power (V+) → Power supply to all sensors (check sensor voltage requirements)

Add a 120Ω termination resistor at the last sensor on the bus to reduce signal reflections.

In Teltonika Configurator:

  1. Navigate to RS485 settings
  2. Set RS485 Mode to Fuel Level Sensors (or LLS depending on firmware)
    Configure 5 sensor entries, each with:
  • Sensor ID / Slave Address: 1, 2, 3, 4, 5 (matching the physical sensor addresses)

Thanks

3

Hi @Ashutosh.Singh

Thank you for your answer.