LIGO AIR User Guide

Safety Information

This user guide must be read in full before installing or operating the LIGO AIR fuel level sensor. Installation must be performed by qualified technicians, engineers, or system integrators familiar with fuel tank handling and intrinsic-safety practices.

⚠️ DANGER — Fire / Explosion Hazard
For gasoline fuel tanks, all fuel vapors must be completely removed before installation. Empty, clean and dry the tank thoroughly. Failure to do so may cause fire or explosion during drilling and mechanical work.

⚠️ WARNING — Signal Integrity & Cybersecurity
Install the sensor with the directional arrow on the cover pointing toward the receiving device. Ensure RSSI at the receiver is not less than −80 dBm. Use a LIGO PRO or LIGO AIR Adapter if signal is weaker. Change the default password provided by the manufacturer immediately after first pairing to prevent unauthorized access.

⚠️ CAUTION — Mechanical Constraints
Minimum tube length after cutting: 150 mm (15 cm). No metal plate must cover the sensor head — it will block the Bluetooth signal. Maintain a minimum 150 mm clearance between the top of the sensor and any overhead metal surface. Avoid contact with reinforcement ribs or other equipment inside the tank.

ℹ️ NOTICE — Required PPE & Conditions
Wear fuel-resistant gloves and eye protection. Work in a well-ventilated area, away from open flames and ignition sources. Follow local regulations for handling flammable liquids.

Product Overview

The LIGO AIR is a precision Bluetooth fuel level sensor designed by SOJI Electronics for accurate, reliable measurement of fuel levels in tanks. It targets fleet telematics, industrial fuel storage, and vehicle fuel monitoring applications. Built on Bluetooth 5.4 with a sealed IP69K housing and a Li-SOCl₂ primary battery rated for ~10 years of service, the sensor transmits level data wirelessly to a paired telematics device or gateway — eliminating wired sensor harnesses.

Two product families are available: the standard LIGO AIR (LxS / LxT) and the long-range LIGO AIR PRO (Lx S) with higher TX power for challenging environments.

Intended Use

Fleet vehicle fuel monitoring (trucks, buses, construction equipment).
Stationary fuel storage tanks at depots and job sites.
Telematics integration via Bluetooth-capable tracker devices.
Diesel, gasoline, and compatible liquid fuel measurement.

Product Variants

Manufacturer Part Number	Standard Length L (mm)	Notes
LIGO AIR – L7S / L7T, LIGO AIR PRO – L7S	700 ± 3
LIGO AIR – L10S / L10T, LIGO AIR PRO – L10S	1000 ± 3
LIGO AIR – L15S / L15T, LIGO AIR PRO – L15S	1500 ± 3
Custom lengths	up to 6000 mm	Contact manufacturer for customised lengths.

Package Contents

Verify all items are present before installation. Contact support if any item is missing or damaged.

No.	Item	Quantity
1	LIGO AIR Fuel Level Sensor (standard lengths 700 / 1000 / 1500 mm; custom lengths on request)	01
2	Oil filter	01
3	Gasoline-resistant rubber gasket	01
4	Bottom-stop and springs	01
5	Self-drilling screw M4.8 × 32 mm	05
6	Rivet and screw M5 × 20 mm	05
7	Protective cap	01
8	User manual	01

Specifications

Technical Specifications

Parameter	LIGO AIR (LxS, LxT)	LIGO AIR PRO	Unit
Standard length (L)	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	19.5	dBm
Advertising Protocol	SOJI Protocol (default); Mielta Protocol or Escort Protocol (configurable via mobile app)
Power supply	Li-SOCl₂ 3.6 V × 2600 mAh	Li-SOCl₂ 3.6 V × 3600 mAh
Current consumption (working mode)	9	27	µA
Measurement interval	5 to 10		s
Advertising message interval	5 to 10	10 to 15	s
Ingress protection rating	IP69K
Operating temperature	−40 to +85		°C
Resolution	12		bit
Accelerometer	Built-in
Memory	Built-in 32 Mb EEPROM
Average sampling period	5 to 60		s
Temperature measurement absolute error	± 2		°C
Average service life (expected)	10		years
Storage condition	15 °C to 30 °C, RH < 60 %

Dimensions

See mechanical drawing:

Installation

Before installation: Read the Safety Information section in full.

Tools Required

Drill with Ø42 mm hole saw + Ø7 mm drill bit
Tube cutter or hacksaw + deburring tool
Screwdriver (for M4.8 self-drilling screws or M5 rivet nut tool)
Fuel-resistant RTV silicone gasket maker
Smartphone (iOS or Android) with LIGO BLE Configurator app installed
PPE: fuel-resistant gloves, safety glasses, ventilation

Step 1: Site / Fuel Tank Preparation

Empty the tank, then clean and dry it. For gasoline tanks, purge all fuel vapors before drilling to prevent fire or explosion.
Select the installation location:
- As close as possible to the geometric center of the tank, at the deepest point.
- Avoid contact with reinforcement ribs or any internal equipment.
- Mounting orientation must allow the directional arrow on the sensor cover to point toward the receiving device (max signal transmission direction).
Drill the central hole Ø42 mm, then drill four additional Ø7 mm holes for mounting screws.

Mounting hardware selection by tank wall thickness:

Wall Thickness	Recommended Fastener	Mounting Hole
≤ 3 mm	M5 rivet nut	4 × Ø7 mm
> 3 mm	M4.8 self-tapping screw	4 × Ø7 mm

Step 2: Sensor Preparation

Cut the sensor tube to length:

 L = H − 25 mm

Where:

L — final tube length after cutting
H — height of the tank at the installation point

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

⚠️ CAUTION — Minimum Tube Length
The tube length after cutting must be at least 150 mm (15 cm). Shorter tubes are not supported.

Install the bottom-stop, springs, and oil filter onto the tube in sequence.

Step 3: Mounting on the Fuel Tank

Apply fuel-resistant RTV silicone gasket maker to the fuel tank surface, gasket, and sensor flange.
Insert the LIGO AIR sensor into the tank.
Fasten securely using the appropriate fasteners (self-tapping screws or rivet nut as per wall thickness above).
Confirm the directional arrow on the cover points toward the receiving device.

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LIGO AIR mounting on fuel tank

Step 4: Verification

Confirm a minimum 150 mm clearance between the sensor top and any overhead metal surface.
Confirm no metal plate covers the sensor head.
Power-cycle/wake the sensor and proceed to Configuration.

Configuration

Mobile Application

Download LIGO BLE Configurator:

iOS — App Store
Android — Google Play

ℹ️ NOTICE — Permissions
For full operation, grant all permissions requested by the app (Bluetooth, location, storage).

Detailed app usage is documented in the LIGO BLE Configurator App User Guide.

Connecting Sensor

Open the LIGO BLE Configurator app.
The app scans for nearby LIGO AIR sensors.
Select the target sensor from the discovered list to establish a Bluetooth connection.
When prompted, enter the device password. Change the default password immediately after the first successful connection.

Calibration: Set Empty and Set Full

After mounting and pairing, calibrate the sensor before deployment:

Step 1 — Set Full:

Immerse the sensor in fuel until the fuel reaches the sensor flange.
Wait for the C_working value to stabilize.
Press Set Full.

Step 2 — Set Empty:

Remove the sensor from the fuel.
Wait 1–2 minutes to allow fuel to drain from the measuring probe.
Press Set Empty.

Configurable Parameters

Parameter	Default	Range / Options	Description
Advertising Protocol	SOJI Protocol	SOJI / Mielta / Escort	Output protocol for the advertising message.
Measurement interval	—	5 – 10 s	How often the sensor samples the fuel level.
Advertising interval	—	5 – 10 s (AIR) / 10 – 15 s (PRO)	How often advertising messages are broadcast.
Average sampling period	—	5 – 60 s	Averaging window for the reported value.
Password	Manufacturer default	User-defined	Must be changed at first setup.

Operation

Reading Data

The sensor broadcasts level data over Bluetooth advertising. Data is received by a paired telematics tracker, gateway, or the LIGO BLE Configurator app, then forwarded to a telematics platform or fleet management server.

Calibration Methods

Method	Description	Recommended
Calibration on the Platform (server)	Sensor sends raw level values (0–4095) to the server via the telematics device; the platform converts to volume (liters) using a calibration table.	✅ Recommended by manufacturer for LIGO AIR.
Calibration on the Sensor	Sensor directly transmits volume values (liters) based on an internal calibration table.

Long-Range Operation

For long-distance transmission or environments with metal obstacles causing signal attenuation, choose LIGO AIR PRO (higher TX power) or add a LIGO AIR Adapter on the receiver side to boost signal reception.

Device Combination	Bluetooth Signal Range
LIGO AIR + Telematics (tracker) device	Standard distance
LIGO AIR + LIGO AIR Adapter	2 × Standard distance
LIGO AIR PRO + LIGO AIR Adapter	4 × Standard distance

Protective Accessories

Protective cap — install after the sensor is mounted and calibration is complete. The cap prevents unauthorized access and protects against UV, impact, and other environmental factors.

Install: push the cap down until it clicks into place, indicating it is fully seated.
Remove (for inspection): follow the removal procedure shown in the user manual to avoid damaging sensor parts.

⚠️ CAUTION — Cap Removal
Ensure no sensor parts are damaged while removing the protective cap.

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
Level reading unstable / not stabilizing during Set Full	Fuel level below sensor flange Air bubbles in measuring tube Tube not properly cleaned after cutting	Top up fuel until it reaches the flange Wait longer (>2 min) for stabilization Remove sensor, clean tube with fuel, re-install
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.

Cleaning

Clean the external housing with a soft cloth and mild detergent.
For the measuring tube, clean with clean fuel.
Do NOT use solvents, abrasive materials, high-pressure water jets directed at the cover, or alcohol-based cleaners on the sealed electronics housing (IP69K rating preserved only when housing is intact).

Calibration Verification

After any maintenance that disturbs the sensor mounting or tube, re-run the Set Full / Set Empty procedure (see Configuration).

Battery Replacement

The Li-SOCl₂ battery is sealed inside the device and is not user-replaceable. When the sensor reaches end of service life (~10 years), replace the entire unit and recycle the old unit per local WEEE / battery regulations.

⚠️ WARNING — Battery Safety
Do not attempt to open the sensor housing or replace the internal battery. Li-SOCl₂ cells can leak, vent, or rupture if mishandled. Return spent units to SOJI Electronics or an authorised recycler.

Disposal / End-of-Life

Recycle per WEEE Directive (EU 2012/19/EU) and local equivalents.
Lithium battery — return to a certified battery recycling facility.
Do not incinerate or crush the unit.

Certification / Compliance

Warranty period, exclusions, and void conditions are defined in the SOJI Electronics standard warranty terms. Contact Support for the current warranty document.

Support / Contact

Channel	Detail
Website	sojielectronics.com
Email	support@sojielectronics.com
Phone	+84 24 62 932 369
Address	SOJI Electronics Joint Stock Company — (see official website for current address)
Service hours	Mon – Fri, 08:00 – 17:00 GMT+7

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