LIGO AIR User Guide

Safety Information

ℹ️ NOTICE — Important notes during sensor installation

Install the sensor in the direction of maximum signal transmission (the directional arrow on the sensor cover should point toward the receiving device). Minimum allowable length of the measuring probe is 150 mm. Make sure there is no metal plate covering the sensor head, as this may block Bluetooth signal. Ensure that the signal strength (RSSI) at the receiving device is not less than -80 dBm. In cases of weak signal, it is necessary to use a LIGO PRO or a LIGO AIR Adapter to ensure the transmission strength remains within the acceptable range. Change the default password provided by the manufacturer to prevent unauthorized access. Detailed instructions for using mobile application (LIGO BLE configurator) are described in detail in the ‘LIGO BLE Configurator App User Guide’ document.

Product Overview

This user guide provides detailed instructions for the proper installation of the LIGO AIR fuel level sensor. The guide is intended for technicians, engineers, system integrators and end-users who are responsible for installing and maintaining the sensor in a variety of fuel tanks and vehicles.

The LIGO AIR fuel level sensor is a precision device designed by SOJI Electronics to measure the level of fuel in tanks with high accuracy and reliability. Correct installation is critical to ensure optimal performance and long-term durability.

Please read this guide thoroughly before beginning the installation process. Following the steps and recommendations provided will help you avoid common issues and ensure safe, effective operation of the sensor.

Package Contents

No.	Description	Qty (pcs)
1	LIGO AIR Fuel Level Sensor. Standard lengths: 700, 1000, and 1500mm (for customized lengths, please contact the manufacturer)	01
2	Oil filter	01
3	Gasoline-resistant rubber gasket	01
4	Bottom-stop and springs	01
5	Self-drilling screw M4.8x32mm	05
6	Rivet and screw M5x20mm	05
7	Protective cap	01
8	User manual	01

Specifications

Technical specifications

Parameter	LIGO AIR (LxS and LxT)	LIGO AIR-PRO
Standard length (L), mm	700, 1000, 1500...up to 6000 mm
Measuring error, %	± 0.5 %
Bluetooth specs	Bluetooth 5.4, IEEE 802.15.4-2006, 2.4 GHz, -95 dBm sensitivity
TX power max	6 dBm	19.5 dBm
Advertising Protocol	- SOJI Protocol (default) - Mielta Protocol (setting in mobile app) - Escort Protocol (setting in mobile app) - Technoton Protocol (setting in mobile app) - EUROSEN Protocol (setting in mobile app)
Power supply: Built-in Battery Li-SOCL2	3.6V * 2600mAh	3.6V * 3600mAh
Current consumption in working mode (uA)	9	27
Measurement interval (second)	From 5 to 10
Advertising message interval (second)	From 5 to 10	10
Waterproof standard (Ingress protection rating, IP)	IP69K
Operating temperature (°C)	-40...+85
Resolution (bit)	12
Accelerometer	LxS N/A, LxT built-in	Built-in
Memory	Built-in 32Mb EEPROM
Average sampling period, s	5 to 60
Absolute error in temperature measurement within the entire temperature measuring range, °С	±2
Average service life, years (expected)	10 years
Storage condition	15°C to 30°C, RH < 60%

Overview of sensor structure

Figure 1. LIGO AIR series' overall dimensions (mm).

Manufacturer part number	L (mm)
LIGO AIR – L7S LIGO AIR – L7T LIGO AIR PRO – L7S	700 ± 3
LIGO AIR – L10S LIGO AIR – L10T LIGO AIR PRO – L10S	1000 ± 3
LIGO AIR – L15S LIGO AIR – L15T LIGO AIR PRO – L15S	1500 ± 3

Installation

Fuel tank preparation

1. Empty the tank, clean and dry it if necessary, for gasoline fuel tanks, all fuel vapors must be removed from the tank to prevent fire or explosion during installation.
2. Selecting the installation location for the LIGO AIR fuel level sensor, take the following requirements into account:
   • The sensor's installation location must be as close as possible to the tank's geometric center and at its deepest point.
   • The sensor's installation location must be as close as possible to the tank's geometric center and at its deepest point.
   • Ensure that the sensor must avoid contact with reinforcement ribs and other equipment inside the tank.

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Figure 2. Tank installation location requirements

3. Drilling a central hole (Ø42 mm), then drill four additional holes for mounting screws as shown in the figure below:

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Figure 3. Drilling central hole Ø42 mm and four mounting screw holes

Notes: The mounting hole diameter depends on the material and thickness of the tank

• For fuel tanks with a wall thickness ≤3 mm, M5 rivet nut should be used. In this case, Drill 4 × Ø7 mm mounting screw holes.
• For fuel tanks with a wall thickness >3 mm, M4.8 self-tapping screw can be used. In this case, Drill 4 × Ø7 mm mounting screw holes.
• Mounting holes positions must ensure that the sensor is installed in the direction of maximum signal transmission (the directional arrow on the sensor cover should point toward the receiving device).

Sensor preparation

1. Cutting sensor tube

The length of the sensor tube should be calculated according to the following formula:

 L = H - 25 mm

Where:

• L – final tube length after cutting
• H - height of the tank at the installation point.

After cutting, remove any burrs and clean the tube using fuel.

Note: The minimum length of the tube after cutting must be at least 150 mm (15cm)

2. Installing bottom-stop springs and filter

Installing the bottom-stop and the oil filter in sequence, as shown in the figure below:

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Figure 4. Installing bottom-stop springs and oil filter

Installing sensor on the fuel tank

1. Apply gasket sealant to fuel tank, gasket and sensor flange (using Fuel resistant RTV Silicone gasket maker).
2. Insert the LIGO AIR fuel sensor into the tank and secure fasten it securely using the appropriate screws (using self-tapping screws or rivet nut depending on fuel tank thickness and material as mentioned above).

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Figure 5. Installing sensor on the fuel tank

Note: Install the sensor in the direction of maximum signal transmission (the directional arrow on the sensor cover should point toward the receiving device).

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Figure 6. Minimum 150 mm clearance between sensor top and overhead metal surface

Note: Ensure a minimum clearance of 150 mm between the top of the sensor and any overhead metal surface.

Installing protective cap

The protective cap should be installed after the sensor installation and calibration processes are completed. This cap helps prevent unauthorized access and protects the sensor from environmental factors such as sunlight, physical impact…

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Figure 7. Installing protective cap

Push the protective cap until it clicks into place, indicating that it is fully seated.

In cases when sensor inspection is required, the protective cap must be removed. Follow the removal procedure as shown in picture below:

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Figure 8. Protective cap removal procedure

Note: Please ensure that no parts of the sensor are damaged while removing the protective cap.

Configuration

Connecting sensor to smartphone and setting

To configure the LIGO AIR fuel sensor, download the LIGO BLE Configurator app on Appstore (for IOS) or CH Play (for Android devices).

Hereinafter LIGO BLE Configurator is referred to as the "application" or "app".

Note: For full operation, you must grant all the permissions requested by the app

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  Figure 9. Grant all the permissions request by program
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  Figure 10. Grant all the permissions request by program

Grant all the permissions request by program as above

Connecting sensor

Run the application and select the sensor you want to connect to, as shown in the pictures below:

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  Figure 11. Selecting sensor type
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  Figure 12. Connecting sensor

Set Empty and Set Full

Step 1: Set Full

• Immerse the sensor in fuel until the fuel reaches the sensor flange
• Wait for C_working value to stablize and then press Set Full button

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Figure 13. Set Full

Step 2: Set Empty

• Remove the sensor from the fuel and wait for 1-2 minutes allow the fuel drain from the measuring probe and then press Set Empty button.

Figure 14. Set Empty

Calibration table

After installation, the sensor must be calibrated to ensure accurate volume measurement. Calibration table can be performed either on the platform (server) or locally on the sensor.

• Calibration table on the Platform (Server): The sensor sends raw level values (ranging from 0 to 4095) to the server via the telematic device. The platform uses a calibration table to convert these values into volume (liters).
• Calibration table on the Sensor: The sensor directly sends volume values (liters) based on the internal calibration table.

Note: For LIGO AIR sensors, the manufacturer recommends performing calibration table on the platform.

Operation

Solutions for long-range or in metal-obstructed environments

In some cases, when the distance between the sensor and the receiver is long or there are many metal obstacles causing signal attenuation, customers can choose the LIGO AIR PRO model to increase transmission power or install the LIGO AIR Adapter at the receiver side to boost the signal received from the sensor.

Below is a comparison table of transmission distances between different types of sensors and receivers:

Device	Bluetooth signal range
LIGO AIR + Telematics (tracker) device	Standard distance
LIGO AIR + LIGO AIR Adapter	2 x Standard distance
LIGO AIR Pro + LIGO AIR Adapter	4 x Standard distance

Troubleshooting

Symptom	Possible Cause	Solution
Sensor not discovered by LIGO BLE Configurator app	Sensor outside Bluetooth range Metal obstruction blocking sensor head Sensor battery depleted (end of service life) App permissions not granted	Move within range; verify line-of-sight Remove any metal plate above sensor Verify sensor age vs ~10-year service life Re-grant Bluetooth & location permissions
RSSI at receiver below −80 dBm	Distance too far Metal obstruction in signal path Sensor orientation wrong (arrow not toward receiver)	Use LIGO AIR PRO or add LIGO AIR Adapter Re-route or remove obstruction Re-mount sensor so directional arrow points to receiver
Reading shows 0% after Set Empty when fuel is present	Set Empty / Set Full procedure executed in wrong order Tube damaged or burrs not removed	Repeat calibration: Set Full first (immersed), then Set Empty (drained) Inspect tube, deburr, re-cut if necessary
Cannot connect with default password (login refused)	Default password already changed by previous user	Contact the previous installer or factory-reset via support

If the problem persists, contact Support.

Maintenance

Periodic Inspection

Frequency	Action
Monthly	Visual inspection of sensor cover, cable entry, and protective cap for damage or tampering.
Quarterly	Verify RSSI ≥ −80 dBm at receiver; check directional alignment.
Annually	Verify calibration on the platform; confirm advertising protocol/interval settings.
~10 years (end of service life)	Replace sensor — Li-SOCl₂ primary battery is non-replaceable; expected service life is 10 years.

Certification / Compliance

Refer to LIGO AIR Certification & Approvals for current certificate status.

Support / Contact

Channel	Detail
Company	SOJI ELECTRONICS.,JSC
Address	C50-LK13, Lot No. 09, New Urban Area, Le Trong Tan street, Duong Noi Ward, Ha Dong District, Hanoi City, Vietnam
Tel/Fax	+84 24 62 932 369
Email	contact@sojielectronics.com
Website	sojielectronics.com

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