Fuel level sensor

For measurement of fuel in a car tank are used float sensors:

• сontinuous operation, with a rheostat as a sensitive element;
• discrete, with magnet sensitive seals contacts and a magnetic float.

Among mechanical sensors the most widespread are:

• capacity sensor, measuring electrical capacity of the condenser filled with fuel;
• ultrasonic, measuring time of reflections from a sound wave of section of the environments fuel-air.

Float sensor

Price of float sensors is around $50,  what is the main advantage. The measurement error is 10-30%.

To the lacks of float sensors concerns presence of mechanical elements which wear out. If as a measuring element the rheostat is applied, its  finger with time begins to loose contact and system receives sharp oscillations or dips of value. The shoulder of lever of the sensor can be bent that brings an additional lapse in measurements.

Construction of float sensors of lorries Volvo, MAN is other: instead of rheostat in them is applied the ruler of tight magnet sensitive contact pieces (sealed-contact), placed in an aluminum tube on which the floater slides. By its principle such sensors are less subject to wear, however they show other lack: step character of outgoing signal, level is measured by steps 20-30 mm, that approximately corresponds 25l.

Besides, if the tube is deformed, the floater starts to "hang" and the system works incorrectly.

Ultrasonic sensor

Price of ultrasonic sensors is around $500-$2500, measurement error is near 0,5%.

Ultrasonic sensor  with high precision measures distance till division of environments air-fuel. For measurement ultrasonic radiator-receiver is used, with the help of which the wave package is radiated and time of its reflection from border of section of environments is defined.

Advantage of ultrasonic sensors is an absence of any contact with fuel, independence of indications of fuel parameters. Also  application of ultrasonic sensors is justified for measurement of level of liquids with an unstable chemical compound (the products of oil extract containing sheeted water, etc.). Application of ultrasonic sensors doesn't demand mechanic intervention in a construction of tanks that allows to apply them to work with explosive liquids and doesn't demand drainage of capacities during installation.

Ultrasonic sensors are used only for decisions of specific tasks because of the high price.

Capacitor sensors

Price of capacitor sensors is within limits $150-$300, measurement error is near 1% (1mm).

In the name «capacitor» means  the principle of measurement of fuel level by an electric reservoir of the condenser, formed by two tubes lowered in a tank. Capacity of measurement condenser is measured at different levels of filling of the sensor by dielectric which fuel is.

Advantages of capacitor sensors are absence of mechanic moving parts and rather low price. To lacks we can carry dependence of indications on fuel temperature and sensitivity to availability of various additions, water.

Original car sensors (by supplier)

Original car sensors more often are float sensors and their purpose is to display necessity of refueling proximately and on time.

Use of regular car sensor of fuel level as a part of the additional monitoring system (GPS+fuel)  is difficult because of impossibility to disconnect it from the existing scheme of measurement and work in parallel with the regular scheme can bring essential errors as in work of the indicator of level on the instrument panel, and in the data on an exit of the regular monitoring system of fuel.

The sourсes of errors are:

• scheme of inclusion of the original sensor differs even among different models of one manufacturer and it is necessary to make changes to electronics of entrance chains of the measuring block;
• supply voltage of a circuit of the level sensor often is unstable and at change of sensor engine turns can "swim" in limits 10-20l that isn't essentially for the regular indicator having 3-5 divisions: "full", "half", "empty";
• periodical level measurement, while onboard computer runs measurement process periodically for the short time only.

General recommendations

LTD "ISTRIM" offers a number of operations of technical development of methods for tank calibration and measurement of fuel with the help of level sensors

By our experience, fuel oscillations in a tank during driving and at driving at an angles constitute 10-60l depending on a configuration of a tank and character of driving of a vehicle.

Optimal variant on a ratio the price/quality are capacity level sensors with the frequency output (for example, «Strela -CH» or DUT-Е) in a complex with adapter IS12. The price of capacity sensors of  fuel level depends on tank altitude and the size for your order. To know whole price of your auto fleet, please contact to our sales department

During installation of fuel level sensors it is important to observe following conditions:

• to install sensor in geometrical center of a tank;
• connections of the sensor with the electronic block should be the shortest and, whenever it's possible, protected from mechanical damages;
• it's important, that the data from the sensor was transferred on the digital interface with maximum protection ;
• the measurement system has to make calculation of fuel volume into liters on board in order to exclude discrepancy and mess with calibration tables on the server of dispatching system.