Ultrasonic level sensor Sigma

SIGMA ULS non-invasive ultrasonic level sensor. Can be used to measure level of liquids in reservoirs, including LPG in the vehicles tanks. Sensor is fastened to the bottom of the tank and do not have direct contact with the liquid. The device allows us to measure level of water, LPG (propane-butane) and other fluids. Sensor is compatible with various control units, data concentrators and GPS tracking equipment.

Main features:

  • Low cost;
  • Non-invasive;
  • Easy installation;
  • Measuring error 2%.





Sensor description

Ultrasonic level sensor “SIGMA” allows with high accuracy to determine LPG consumption from one refueling to another and plan a visit to the gas station.

The sensor uses ultrasonic measuring principle. Ultrasonic wave goes from the bottom of the tank to the top, reflects and goes back to the bottom.

Operation principle

 Sensor consists of two parts - measuring part and transducer with indicator (hereinafter - Transducer). 


  a b  
  Typical LPG fuel containers layout and recommended position for sensor measuring part installation in passenger cars (a - toroidal container, b - cylindrical container)   


Transducer calculates fuel level by processing data from the measuring part and outputs result to the indicator. Calibration procedure is performed to indicate fuel volume instead of fuel level. After the calibration, fuel level (in centimeters) is recalculated into volume (liters). Measuring results are demonstrated on the indicator; they can be also transferred to the GPS tracking device for further processing. 

Converter calculates fuel level according to the measuring device data and shows readings on the indicator display in liters.

Indicator displays the remaining amount of fuel in its basic operation mode.

Typical placement of converter with the indicator (it can also be mounted on a horizontal surface using the mounting bracket from the delivery pack)


To determine the filled-in fuel during refueling: you should press Button 1 (lower one) before refueling, then you should press Button 2 (upper one) to set up the reference level of fuel.
After the refueling, indicator will show the amount of filled-in fuel, excluding the initial fuel in the tank. You can switch between the basic operation mode and refueling mode pressing Button 1.

There are 3 modifications of SIGMA ULS sensors, which have different data interface for setting:
SIGMA ULS - no data transfer interface (setting by battons);
SIGMA ULS2 - RS-232 interface for setting;
SIGMA ULS4 - RS-485 interface for setting.
To protect the sensor from mechanical influences and unauthorized access to the sensor and its mounting system, a ULM.4000 protection device can be used (optionally) on horizontally located fuel gas ballons up to 450 mm in diameter mounted outside the vehicle.
Sensor installation does not interfere with the tank structure or influence autogas equipment operation.
Sensor can be used with equipment that supports unified communication protocol Epsilon Data Exchange.

Installation of the sensor

The best places for measuring part installation are cavities and hollow spaces in the vehicle trunk bottom. Distance between the bottom, trunk walls and measuring part must be no less than 5 mm (see picture). To achieve this, rubber spacers may be used. Spacers must be positioned in a way that container remains in horizontal position.

Measuring part position in the vehicle trunk hollow space

Another solution for installation can be cutting Ø 40 – 50 mm hole in the trunk bottom, where the measuring part can be placed. Hole can be hermetically sealed afterwards with a slab of rubber sheet or with matching blanking plug (user-supplied).
Measuring part working surface should be parallel to fuel surface, in other words – horizontally.

Potential installation place of measuring part on a toroidal container

Considering information above, chose two, three potential installation places of measuring part, clean them from dirt and rust, degrease and mark them.


Tank calibration

Calibration could be done in 2 ways:

  • using digital indicator
  • using installation software

Each of this ways could be performed as in automatic so manual mode.

For more detailed information please read installation manual in the download section.


Technical characteristics


Description Unit Value Notes
Type of measured fuel


Allowed tilt angle of vehicle when measuring level, max degrees 12  
Container wall thickness mm  1,5…4,0  
Operational temperature range oС – 40 … + 70  
Measuring part ingress protection rating   IP67  
Transducer ingress protection rating   IP50  
Mode of operation   Continuous  
Indicator resolution capability liters  1* 


Measurement range mm  20…600**  
Averaging period sec. 30


Code length of presentation of measurement results bit 10/12/16 Level
8 Temperature
Exchange rate through the serial port bps 2400, 4800, 9600, 19200, 38400, 57600, 115200 Programmed, default setting - 19200
Power Supply
Power supply voltage, operational range  V +9 …+36  Nominal value
Current consumption, max  mA 70  
Digital   RS-485 ULS4 model
RS-232 ULS2 model
- transducer, max  mm 62х38х16  
- measuring part, max  mm ∅26х11  
Notes to table:

* - Indicator readings are considered adequate in 30 seconds after the filling-in if the vehicle stays in horizontal position.
** - When level of fuel in tank is lower than the minimal measuring range of sensor, readings can be incorrect. It is recommended to fill in before fuel reaches lower measuring range of sensor.




Contact details


Novozabarskaya Str. 2/6

Kiev, Ukraine 04074

Email Address

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Phone Number

+38 093 887 46 26

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