LIGO AIR User Guide

LIGO AIR User Guide v1.2 — Wireless Fuel Level Sensor Document version: 1.2 | Date: 04/11/2025 | Language: English

Safety Information

Read this section completely before installation or operation. Failure to observe these warnings may result in serious injury, death, or damage to equipment.

The LIGO AIR fuel level sensor must be installed and operated only by qualified technicians familiar with fuel tank systems, electrical safety, and wireless device installation. Personal Protective Equipment (PPE) is required during installation.

⚠️ DANGER — Fire / Explosion Hazard

Hazard: Fuel vapors are highly flammable and can ignite from sparks, open flames, or static electricity Consequence: Serious injury, death, or destruction of vehicle/equipment Required action: Before drilling or installation, completely empty the fuel tank and ventilate all residual vapors. Use only non-sparking tools. Maintain fire extinguisher within 5 meters. No smoking or open flames within 10 meters of work area.

Product Overview

The LIGO AIR is a wireless fuel level sensor designed and manufactured by SOJI Electronics for measuring the level of liquid fuel and other non-conductive liquids in vehicle tanks and stationary fuel storage applications.

Equipped with Bluetooth Low Energy 5.4 technology, LIGO AIR enables seamless, real-time data transmission without requiring complex wiring. The heavy-duty metal structure provides protection against dust, moisture, vibration, and high-temperature environments.

Intended Use

LIGO AIR is intended for:

• Fuel level measurement in diesel, gasoline, and non-conductive liquid tanks
• Mobile applications: trucks, excavators, cement mixers, construction machinery
• Stationary applications: marine vessels, generators, industrial oil storage tanks
• Off-highway machinery in harsh environments

Product Variants

Variant	Description	Battery Life	Range
LIGO AIR LxS	Standard cost-effective version	6–8 years	Standard
LIGO AIR LxT	Extended-battery version	8–12 years	Standard
LIGO AIR PRO	Long-range version (high TX power)	6–8 years	2× Standard

Package Contents

Each LIGO AIR shipment includes:

No.	Item	Quantity
1	LIGO AIR Fuel Level Sensor (700/1000/1500 mm standard, custom 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	Quick installation manual	01

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

Specifications

Parameter	LIGO AIR (LxS, 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	TX power max: 19.5 dBm
Advertising Protocol	SOJI (default), Mielta, Escort — selectable in mobile app
Power supply	3.6V × 2600mAh (LxS) / 2400mAh (LxT) Li-SOCl₂	3.6V × 3600mAh
Current (working mode), µA	9	27
Measurement interval (s)	5 to 10
Advertising interval (s)	5 to 10	10 to 15
Ingress protection	IP69K
Operating temperature (°C)	-40 to +85
Resolution (bit)	12
Accelerometer	N/A	Built-in
Memory	Built-in 32 Mb EEPROM
Service life (expected), years	10
Storage condition	15 °C to 30 °C, RH < 60 %

Sensor Dimensions

File:LIGO-AIR-dimensions.png

LIGO AIR overall dimensions (mm)

Part Number	Length L (mm)
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

Installation

Before installation: Read Safety Information section thoroughly.

Tools Required

• Electric drill with Ø4 mm and Ø42 mm bits
• M4.8 self-tapping screw driver (or M5 rivet tool depending on tank thickness)
• Cutting tool for sensor tube (hacksaw or pipe cutter)
• Deburring tool
• Fuel-resistant RTV silicone gasket sealant
• Mobile phone with LIGO BLE Configurator app installed
• Personal Protective Equipment (PPE): safety goggles, chemical-resistant gloves

Step 1: Fuel Tank Preparation

1. Empty the fuel tank completely. For gasoline tanks, ventilate all fuel vapors to prevent fire/explosion (see Safety)
2. Clean and dry the tank interior
3. Select installation location:
   • As close as possible to the tank's geometric center
   • At the tank's deepest point
   • Avoid contact with reinforcement ribs or internal equipment

File:LIGO-AIR-tank-location.png

Installation location — front, left, and top view

Step 2: Drilling Mounting Holes

Drill a central hole (Ø42 mm) and four mounting holes (Ø7 mm) as shown:

File:LIGO-AIR-drilling-pattern.png

Drilling pattern: Ø40 center hole + 4 × Ø4 mounting holes at 70.5 × 70.5 mm spacing

Tank wall thickness	Fastener type	Mounting hole
≤ 3 mm	M5 rivet nut	4 × Ø7 mm
> 3 mm	M4.8 self-tapping screw	4 × Ø7 mm

ℹ️ NOTICE — Sensor Orientation
Mounting hole positions must ensure the sensor's directional arrow points toward the BLE receiver. Incorrect orientation will severely reduce wireless range.

Step 3: Sensor Tube 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:

1. Remove all burrs with deburring tool
2. Clean the tube interior with fuel

⚠️ WARNING — Tube Preparation
Minimum tube length after cutting is 150 mm (15 cm). Shorter tubes will not function correctly.

Step 4: Install Bottom-Stop and Filter

Install the bottom-stop and oil filter in sequence as shown:

File:LIGO-AIR-bottom-stop-filter.png

Bottom-stop spring and oil filter installation

Step 5: Mount Sensor on Fuel Tank

1. Apply fuel-resistant RTV silicone gasket sealant to:
   • Tank surface around the central hole
   • Gasket (both sides)
   • Sensor flange
2. Insert the LIGO AIR sensor through the central hole
3. Align so the directional arrow points toward the BLE receiver
4. Fasten using appropriate screws (self-tapping or rivet)

File:LIGO-AIR-orientation-examples.png

Correct (✓) vs incorrect (✗) sensor orientations

Step 6: Verify Installation Clearance

Ensure a minimum clearance of 150 mm between the top of the sensor and any overhead metal surface to avoid BLE signal attenuation.

File:LIGO-AIR-clearance.png

Minimum 150 mm clearance from overhead metal

After mounting, proceed to Configuration.

Configuration

LIGO AIR is configured via the LIGO BLE Configurator mobile application.

Mobile App Installation

Download LIGO BLE Configurator from:

• iOS: App Store
• Android: Google Play

After installation, grant all permissions requested by the app:

• Camera (for QR code scanning)
• Location (required by Android for BLE scanning)
• Nearby devices / Bluetooth

File:LIGO-AIR-app-permissions.png

Granting app permissions

Connecting to the Sensor

1. Open the LIGO BLE Configurator app
2. Tap LIGO AIR in the product list
3. Scan the area — the app will list discovered sensors
4. Tap Connect next to the desired sensor

Each sensor shows:

• Name (e.g., LIGO AIR_7EEF7E7F)
• RSSI (signal strength, should be ≥ -80 dBm)
• Temperature
• Current fuel level
• Battery voltage (Vbat)
• Firmware version (FW)

File:LIGO-AIR-device-list.png

Selecting LIGO AIR from device list

Calibration: Set Empty / Set Full

After installation, calibrate the sensor:

Step 1: Set Full

1. Immerse the sensor in fuel until fuel reaches the sensor flange
2. Wait for C_working value to stabilize (~30 seconds)
3. Press Set Full button in the app

File:LIGO-AIR-set-full.png

Set Full procedure

Step 2: Set Empty

1. Remove the sensor from fuel
2. Wait 1–2 minutes for fuel to drain from the measuring probe
3. Press Set Empty button in the app

File:LIGO-AIR-set-empty.png

Set Empty procedure

Configurable Parameters

Parameter	Default	Range / Options
Device name	LIGO AIR_<MAC>	Customizable
Advertising protocol	SOJI	SOJI / Mielta / Escort
Measurement interval	5–10 s	5 to 60 s
Advertising interval	5–10 s	5–10 s (LIGO AIR), 10–15 s (PRO)
Output mode	0–4095 raw	0–1023 raw / 0–4095 raw / Liters
Password	(default)	CHANGE before deployment

ℹ️ NOTICE — Security Recommendation
Change the default password immediately after first connection to prevent unauthorized configuration changes.

Operation

After installation and calibration, LIGO AIR operates autonomously, transmitting fuel level data via BLE advertising packets at configured intervals.

Calibration Table

LIGO AIR supports two calibration methods:

Method	Description	Recommended
On Platform (Server)	Sensor sends raw values (0–4095). Server converts to volume (liters) using calibration table.	✓ Recommended
On Sensor	Sensor sends volume values directly using internal calibration table.

The manufacturer recommends platform calibration for fleet management scenarios because:

• Single source of truth on the server
• Easier to update calibration across multiple sensors
• Reduces sensor memory load

Reading Sensor Data

LIGO AIR data is received by:

• Telematics device (FM tracker) with BLE scanning
• Smartphone with LIGO BLE Configurator app

For protocol integration details, see Protocol Integration.

Long-Range Operation

For challenging environments (long distance, metal obstacles):

Combination	Range
LIGO AIR + Telematics device	Standard
LIGO AIR + LIGO AIR Adapter	2× Standard
LIGO AIR PRO + LIGO AIR Adapter	4× Standard

Installing the Protective Cap

After installation and calibration are complete, install the protective cap to prevent unauthorized access and protect against environmental damage.

File:LIGO-AIR-cap-install.png

Push the cap until it clicks into place

For inspection, remove the cap as shown:

File:LIGO-AIR-cap-removal.png

Correct (✓) vs incorrect (✗) cap removal procedure

Troubleshooting

Symptom	Possible Cause	Solution
Sensor not found in app's device list	Bluetooth disabled on phone Sensor in storage mode (not yet activated) Sensor out of range (>50 m) Metal obstruction blocking signal	Enable Bluetooth, restart app Move within 1 m of sensor and retry Use LIGO AIR Adapter to boost reception Verify orientation (directional arrow toward receiver)
Connection drops frequently	RSSI weaker than -80 dBm High RF interference (other 2.4 GHz devices) Tank metal interference	Reposition receiver closer Use LIGO AIR PRO + Adapter Reorient sensor (arrow toward receiver)
Fuel reading inaccurate	Calibration error Sensor tube damaged or bent Filter clogged with debris Wrong calibration table on platform	Recalibrate using Set Empty / Set Full Inspect probe, replace if bent Clean or replace oil filter Verify calibration table values
Reading shows fixed value (no change)	Sensor electronics frozen Storage mode not deactivated	Disconnect and reconnect via app Power-cycle by removing/inserting battery
Battery voltage drops rapidly	Battery near end of life (8+ years) Measurement interval too short Operating in temperature extremes	Replace battery (see Maintenance) Increase measurement interval Verify operating temperature within range
Sensor reports incorrect temperature	Sensor near heat source (engine, exhaust) Sensor still warming up after installation	Relocate sensor away from heat sources Wait 10 minutes for thermal equilibrium
App permission denied	Camera/Location/Bluetooth permissions not granted	Phone Settings → Apps → LIGO BLE Configurator → Permissions → Grant all
Forgot password	Custom password set, then lost	Contact SOJI Support (proof of ownership required for reset)

If problem persists after troubleshooting, contact Support.

Maintenance

Periodic Inspection

Frequency	Action
Monthly	Verify sensor reports data via mobile app or telematics platform
Quarterly	Check protective cap integrity. Verify mounting screws still secure.
Annually	Remove sensor, clean filter, inspect probe for damage. Verify gasket seal still functional.
Every 5 years	Check battery voltage trend. If below 3.4V consistently, plan battery replacement.
Every 8–10 years	Replace battery (Li-SOCl₂ 3.6V).

Cleaning

1. Disconnect sensor from fuel tank (drain tank if necessary)
2. Wipe external surface with dry cloth or cloth lightly dampened with non-conductive cleaner
3. Do NOT use:
   • Solvents (acetone, benzene)
   • Abrasive materials
   • High-pressure water beyond IP69K rating
4. Inspect and clean the oil filter — replace if clogged
5. Reinstall with new gasket sealant

Battery Replacement

⚠️ WARNING — Battery Replacement Safety
Replace only with authorized SOJI Li-SOCl₂ 3.6V battery (part numbers vary by variant) Disconnect sensor from fuel tank before opening Ensure work area is ventilated and free of ignition sources Wear chemical-resistant gloves

1. Remove protective cap
2. Loosen 4 mounting screws (do not remove from tank)
3. Lift sensor housing off the tank
4. Open battery compartment per technical instruction
5. Remove old battery — observe polarity
6. Install new battery — match polarity markers
7. Close battery compartment
8. Reassemble sensor and verify operation with mobile app

Calibration Verification

After any maintenance involving probe replacement or modification, re-perform Set Empty / Set Full calibration (see Configuration).

Disposal / End-of-Life

LIGO AIR contains a lithium battery and electronic components subject to WEEE (Waste Electrical and Electronic Equipment) regulations.

1. Remove battery and dispose separately at certified battery recycling facility
2. Send sensor body to electronic waste recycling
3. Do NOT dispose in regular trash or landfill
4. In EU: Take-back via local WEEE registration scheme

Certification / Compliance

LIGO AIR is manufactured to meet international standards and regulations.

Wireless / Radio

Region	Standard / Approval
EU	RED 2014/53/EU, EMC 2014/30/EU
US	FCC Part 15.247
Canada	ISED RSS-247, RSS-Gen, ICES-003
UK	UKCA, UK RED
Japan	MIC (Telec)

Environmental

Standard	Status
RoHS 3 (2011/65/EU + 2015/863)	Compliant
REACH (EU Regulation 1907/2006)	Compliant
WEEE (2012/19/EU)	Registered
Battery WEEE (2006/66/EC)	Registered

Mechanical

Standard	Rating
IEC 60529 (Ingress Protection)	IP69K

Bluetooth Qualification

• Bluetooth Core Specification: 5.4
• Bluetooth SIG Member ID: (see LIGO Air Memberships)
• End Product Declaration ID: (see LIGO Air Memberships)

Detailed certification information: see LIGO Air Certification & Approvals Memberships information: see LIGO Air Memberships

Warranty

• Warranty period: 3 years from date of shipment
• Battery NOT covered by warranty
• Warranty void if:
  • Operating conditions exceed specifications
  • Unauthorized modification or repair
  • Damage from improper installation
  • Damage from chemical exposure outside rated fluids

Contact SOJI Electronics for warranty claims.

Support / Contact

For technical assistance, warranty claims, or product inquiries:

Channel	Contact
Website	sojielectronics.com
Email	support@sojielectronics.com
Phone	(insert customer support number)
Address	(insert SOJI Electronics JSC address)

Related Pages

• LIGO AIR — Product overview
• LIGO AIR Datasheet — Detailed BLE protocol, payload format
• LIGO AIR Certification & Approvals — Full certification list
• Frequently Asked Questions - FAQ — Common questions