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== Safety Information ==
== 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.
=== Important notes during sensor installation ===


{{Danger|title=Fire / Explosion Hazard|body=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.}}
* 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.
{{Warning|title=Signal Integrity & Cybersecurity|body=
* Make sure there is no metal plate covering the sensor head, as this may block Bluetooth signal.
* Install the sensor with the directional arrow on the cover pointing toward the receiving device.
* 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.
* 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 to prevent unauthorized access.
* '''Change the default password''' provided by the manufacturer immediately after first pairing 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.
}}
 
{{Caution|title=Mechanical Constraints|body=
* 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.
}}
 
{{Notice|title=Required PPE & Conditions|body=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 ==
== 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.
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.


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.
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.


=== Intended Use ===
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.
* 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 ===
[[File:LIGO-AIR-product-photo.png|center|700px|thumb|LIGO AIR series Fuel Level Sensor]]
 
{| class="wikitable"
|-
! 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 ==
== Package Contents ==


Verify all items are present before installation. Contact support if any item is missing or damaged.
{| class="wikitable" style="text-align:center;"
 
{| class="wikitable"
|-
|-
! No. !! Item !! Quantity
! No. !! Description !! Qty (pcs)
|-
|-
| 1 || LIGO AIR Fuel Level Sensor (standard lengths 700 / 1000 / 1500 mm; custom lengths on request) || 01
| 1 || style="text-align:left;" | LIGO AIR Fuel Level Sensor. Standard lengths: 700, 1000, and 1500mm (for customized lengths, please contact the manufacturer) || 01
|-
|-
| 2 || Oil filter || 01
| 2 || style="text-align:left;" | Oil filter || 01
|-
|-
| 3 || Gasoline-resistant rubber gasket || 01
| 3 || style="text-align:left;" | Gasoline-resistant rubber gasket || 01
|-
|-
| 4 || Bottom-stop and springs || 01
| 4 || style="text-align:left;" | Bottom-stop and springs || 01
|-
|-
| 5 || Self-drilling screw M4.8 × 32 mm || 05
| 5 || style="text-align:left;" | Self-drilling screw M4.8x32mm || 05
|-
|-
| 6 || Rivet and screw M5 × 20 mm || 05
| 6 || style="text-align:left;" | Rivet and screw M5x20mm || 05
|-
|-
| 7 || Protective cap || 01
| 7 || style="text-align:left;" | Protective cap || 01
|-
|-
| 8 || User manual || 01
| 8 || style="text-align:left;" | User manual || 01
|}
|}


== Specifications ==
== Specifications ==


=== Technical Specifications ===
=== Technical specifications ===


{| class="wikitable"
{| class="wikitable" style="text-align:center;"
|-
|-
! Parameter !! LIGO AIR (LxS, LxT) !! LIGO AIR PRO !! Unit
! Parameter !! LIGO AIR (LxS and LxT) !! LIGO AIR-PRO
|-
|-
| Standard length (L) || colspan="2" style="text-align:center; vertical-align:middle;" | 700, 1000, 1500 … up to 6000 || mm
| style="text-align:left;" | Standard length (L), mm || colspan="2" | 700, 1000, 1500...up to 6000 mm
|-
|-
| Measuring error || colspan="2" style="text-align:center; vertical-align:middle;" | ± 0.5 || %
| style="text-align:left;" | Measuring error, % || colspan="2" | ± 0.5 %
|-
|-
| Bluetooth specs || colspan="2" style="text-align:center; vertical-align:middle;" | Bluetooth 5.4, IEEE 802.15.4-2006, 2.4 GHz, −95 dBm sensitivity ||
| style="text-align:left;" | Bluetooth specs || colspan="2" | Bluetooth 5.4, IEEE 802.15.4-2006, 2.4 GHz, -95 dBm sensitivity
|-
|-
| TX power (max) || style="text-align:center; vertical-align:middle;" | 6 || style="text-align:center; vertical-align:middle;" | 19.5 || dBm
| style="text-align:left;" | TX power max || 6 dBm || 19.5 dBm
|-
|-
| Advertising Protocol || colspan="2" style="text-align:center; vertical-align:middle;" | SOJI Protocol (default); Mielta Protocol or Escort Protocol (configurable via mobile app) ||
| style="text-align:left;" | Advertising Protocol || colspan="2" | - SOJI Protocol (default)<br>- Mielta Protocol (setting in mobile app)<br>- Escort Protocol (setting in mobile app)
|-
|-
| Power supply || style="text-align:center; vertical-align:middle;" | Li-SOCl₂ 3.6 V × 2600 mAh || style="text-align:center; vertical-align:middle;" | Li-SOCl₂ 3.6 V × 3600 mAh ||
| style="text-align:left;" | Power supply: Built-in Battery Li-SOCL2 || 3.6V * 2600mAh || 3.6V * 3600mAh
|-
|-
| Current consumption (working mode) || style="text-align:center; vertical-align:middle;" | 9 || style="text-align:center; vertical-align:middle;" | 27 || µA
| style="text-align:left;" | Current consumption in working mode (uA) || 9 || 27
|-
|-
| Measurement interval || colspan="2" style="text-align:center; vertical-align:middle;" | 5 to 10 || s
| style="text-align:left;" | Measurement interval (second) || colspan="2" | From 5 to 10
|-
|-
| Advertising message interval || style="text-align:center; vertical-align:middle;" | 5 to 10 || style="text-align:center; vertical-align:middle;" | 10 to 15 || s
| style="text-align:left;" | Advertising message interval (second) || From 5 to 10 || From 10 to 15
|-
|-
| Ingress protection rating || colspan="2" style="text-align:center; vertical-align:middle;" | IP69K ||
| style="text-align:left;" | Waterproof standard (Ingress protection rating, IP) || colspan="2" | IP69K
|-
|-
| Operating temperature || colspan="2" style="text-align:center; vertical-align:middle;" | −40 to +85 || °C
| style="text-align:left;" | Operating temperature (°C) || colspan="2" | -40...+85
|-
|-
| Resolution || colspan="2" style="text-align:center; vertical-align:middle;" | 12 || bit
| style="text-align:left;" | Resolution (bit) || colspan="2" | 12
|-
|-
| Accelerometer || colspan="2" style="text-align:center; vertical-align:middle;" | Built-in ||
| style="text-align:left;" | Accelerometer || colspan="2" | Built-in
|-
|-
| Memory || colspan="2" style="text-align:center; vertical-align:middle;" | Built-in 32 Mb EEPROM ||
| style="text-align:left;" | Memory || colspan="2" | Built-in 32Mb EEPROM
|-
|-
| Average sampling period || colspan="2" style="text-align:center; vertical-align:middle;"  | 5 to 60 || s
| style="text-align:left;" | Average sampling period, s || colspan="2" | 5 to 60
|-
|-
| Temperature measurement absolute error || colspan="2" style="text-align:center; vertical-align:middle;" | ± 2 || °C
| style="text-align:left;" | Absolute error in temperature measurement within the entire temperature measuring range, °С || colspan="2" | ±2
|-
|-
| Average service life (expected) || colspan="2" style="text-align:center; vertical-align:middle;" | 10 || years
| style="text-align:left;" | Average service life, years (expected) || colspan="2" | 10 years
|-
|-
| Storage condition || colspan="2" style="text-align:center; vertical-align:middle;" | 15 °C to 30 °C, RH < 60 % ||
| style="text-align:left;" | Storage condition || colspan="2" | 15°C to 30°C, RH < 60%
|}
|}


=== Dimensions ===
=== Overview of sensor structure ===


See mechanical drawing: [[File:LIGO-AIR-dimensions.png|center|640px|thumb|LIGO AIR mechanical dimensions]]
[[File:LIGO-AIR-fig1-sensor-structure.png|center|700px|thumb|Overview of LIGO AIR sensor structure]]
 
{| class="wikitable" style="text-align:center;"
|-
! Manufacturer part number !! L (mm)
|-
| style="text-align:left;" | LIGO AIR – L7S<br>LIGO AIR – L7T<br>LIGO AIR PRO – L7S || 700 ± 3
|-
| style="text-align:left;" | LIGO AIR – L10S<br>LIGO AIR – L10T<br>LIGO AIR PRO – L10S || 1000 ± 3
|-
| style="text-align:left;" | LIGO AIR – L15S<br>LIGO AIR – L15T<br>LIGO AIR PRO – L15S || 1500 ± 3
|}


== Installation ==
== Installation ==


'''Before installation:''' Read the [[#Safety Information|Safety Information]] section in full.
=== Preparation ===
 
==== Fuel tank preparation ====


=== Tools Required ===
# 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.
* Drill with Ø42 mm hole saw + Ø7 mm drill bit
# Selecting the installation location for the LIGO AIR fuel level sensor, take the following requirements into account:
* Tube cutter or hacksaw + deburring tool
#* The sensor's installation location must be as close as possible to the tank's geometric center and at its deepest point.
* Screwdriver (for M4.8 self-drilling screws or M5 rivet nut tool)
#* The sensor's installation location must be as close as possible to the tank's geometric center and at its deepest point.
* Fuel-resistant RTV silicone gasket maker
#* Ensure that the sensor must avoid contact with reinforcement ribs and other equipment inside the tank.
* Smartphone (iOS or Android) with '''LIGO BLE Configurator''' app installed
* PPE: fuel-resistant gloves, safety glasses, ventilation


=== Step 1: Site / Fuel Tank Preparation ===
[[File:LIGO-AIR-fig2-tank-preparation.png|center|700px|thumb|Tank installation location requirements]]


# Empty the tank, then clean and dry it. '''For gasoline tanks, purge all fuel vapors before drilling''' to prevent fire or explosion.
# Drilling a central hole (Ø42 mm), then drill four additional holes for mounting screws as shown in the figure below:
# 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:'''
[[File:LIGO-AIR-fig3-drilling.png|center|700px|thumb|Drilling central hole Ø42 mm and four mounting screw holes]]
{| class="wikitable"
 
|-
Notes: The mounting hole diameter depends on the material and thickness of the tank
! Wall Thickness !! Recommended Fastener !! Mounting Hole
* 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.
| ≤ 3 mm || M5 rivet nut || 4 × Ø7 mm
* 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).
|-
 
| > 3 mm || M4.8 self-tapping screw || 4 × Ø7 mm
==== Sensor preparation ====
|}


=== Step 2: Sensor Preparation ===
'''1. Cutting sensor tube'''


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


   L = H − 25 mm
   L = H - 25 mm


Where:
Where:
* '''L''' — final tube length after cutting
* L – final tube length after cutting
* '''H''' — height of the tank at the installation point
* H - height of the tank at the installation point.
 
After cutting, remove any burrs and clean the tube using fuel.


After cutting, remove all burrs and clean the tube using fuel.
Note: The minimum length of the tube after cutting must be at least 150 mm (15cm)


{{Caution|title=Minimum Tube Length|body=The tube length after cutting '''must be at least 150 mm (15 cm)'''. Shorter tubes are not supported.}}
'''2. Installing bottom-stop springs and filter'''


Install the bottom-stop, springs, and oil filter onto the tube in sequence.
Installing the bottom-stop and the oil filter in sequence, as shown in the figure below:


=== Step 3: Mounting on the Fuel Tank ===
[[File:LIGO-AIR-fig4-bottom-stop-filter.png|center|700px|thumb|Installing bottom-stop springs and oil filter]]


# Apply fuel-resistant RTV silicone gasket maker to the fuel tank surface, gasket, and sensor flange.
=== Installing sensor on the fuel tank ===
# 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.


[[File:LIGO-AIR-clearance.png|center|640px|thumb|LIGO AIR mounting on fuel tank]]
# Apply gasket sealant to fuel tank, gasket and sensor flange (using Fuel resistant RTV Silicone gasket maker).
# 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).


=== Step 4: Verification ===
[[File:LIGO-AIR-fig5-installing-on-tank.png|center|700px|thumb|Installing sensor on the fuel tank]]
* Confirm a minimum '''150 mm clearance''' between the sensor top and any overhead metal surface.
 
* Confirm no metal plate covers the sensor head.
Note: Install the sensor in the direction of maximum signal transmission (the directional arrow on the sensor cover should point toward the receiving device).
* Power-cycle/wake the sensor and proceed to [[#Configuration|Configuration]].
 
[[File:LIGO-AIR-fig6-clearance.png|center|700px|thumb|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…
 
[[File:LIGO-AIR-fig7-protective-cap-install.png|center|700px|thumb|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:
 
[[File:LIGO-AIR-fig8-protective-cap-remove.png|center|700px|thumb|Protective cap removal procedure]]
 
Note: Please ensure that no parts of the sensor are damaged while removing the protective cap.


== Configuration ==
== Configuration ==


=== Mobile Application ===
=== 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
 
<gallery mode="packed" widths="300" heights="500">
File:LIGO-AIR-fig9-app-permissions-1.jpg|Grant all the permissions request by program
File:LIGO-AIR-fig10-app-permissions-2.jpg|Grant all the permissions request by program
</gallery>


Download '''LIGO BLE Configurator''':
Grant all the permissions request by program as above
* iOS — App Store
* Android — Google Play


{{Notice|title=Permissions|body=For full operation, grant all permissions requested by the app (Bluetooth, location, storage).}}
==== Connecting sensor ====


Detailed app usage is documented in the ''LIGO BLE Configurator App User Guide''.
Run the application and select the sensor you want to connect to, as shown in the pictures below:


=== Connecting Sensor ===
<gallery mode="packed" widths="300" heights="500">
File:LIGO-AIR-fig11-connect-1.jpg|Connecting sensor
File:LIGO-AIR-fig12-connect-2.jpg|Connecting sensor
</gallery>


# Open the LIGO BLE Configurator app.
==== Set Empty and Set Full ====
# 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 ===
'''Step 1: Set Full'''


After mounting and pairing, calibrate the sensor before deployment:
* 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


'''Step 1 — Set Full:'''
[[File:LIGO-AIR-fig13-set-full.jpg|center|700px|thumb|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:'''
'''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 ===
* 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.


{| class="wikitable"
[[File:LIGO-AIR-fig14-set-empty.jpg|center|700px|thumb|Set Empty]]
|-
 
! Parameter !! Default !! Range / Options !! Description
=== Calibration table ===
|-
| 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 ==
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.


=== Reading Data ===
* '''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.


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


=== Calibration Methods ===
== Operation ==


{| class="wikitable"
=== Solutions for long-range or in metal-obstructed environments ===
|-
! 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 ===
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.


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


{| class="wikitable"
{| class="wikitable" style="text-align:center;"
|-
|-
! Device Combination !! Bluetooth Signal Range
! Device !! Bluetooth signal range
|-
|-
| LIGO AIR + Telematics (tracker) device || Standard distance
| style="text-align:left;" | LIGO AIR + Telematics (tracker) device || Standard distance
|-
|-
| LIGO AIR + LIGO AIR Adapter || 2 × Standard distance
| style="text-align:left;" | LIGO AIR + LIGO AIR Adapter || 2 x Standard distance
|-
|-
| LIGO AIR PRO + LIGO AIR Adapter || 4 × Standard distance
| style="text-align:left;" | LIGO AIR Pro + LIGO AIR Adapter || 4 x 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|title=Cap Removal|body=Ensure no sensor parts are damaged while removing the protective cap.}}


== Troubleshooting ==
== Troubleshooting ==

Revision as of 03:12, 11 June 2026

Safety Information

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.

File:LIGO-AIR-product-photo.png
LIGO AIR series Fuel Level 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)
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 From 10 to 15
Waterproof standard (Ingress protection rating, IP) IP69K
Operating temperature (°C) -40...+85
Resolution (bit) 12
Accelerometer 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

Error creating thumbnail: Unable to save thumbnail to destination
Overview of LIGO AIR sensor structure
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

Preparation

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.
Error creating thumbnail: Unable to save thumbnail to destination
Tank installation location requirements
  1. Drilling a central hole (Ø42 mm), then drill four additional holes for mounting screws as shown in the figure below:
Error creating thumbnail: Unable to save thumbnail to destination
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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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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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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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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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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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

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:

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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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.
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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
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

Cross-references to other documents.

Revision History

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