Fuel Gauge and its Importance

A fuel gauge is a device that measures the fuel level present in the vehicle. It consists of a sensing or a sending unit which helps to measure the amount of fuel. A gauge or indicator which is placed outside the fuel tank uses the information from the sensing unit to give the measure of fuel.

How do fuel gauges work?
* The sending unit
* The sending unit is placed inside the fuel tank and has a float, made of foam, connected to a thin metallic rod.
* When the float is nearer to the top of the tank, the wiper on the variable resistor rests closer to the grounded side. This offers less resistance and the current flow is more through the sending unit back to the fuel gauge.
* As the level of fuel drops in the tank, the float sinks and the wiper moves resulting in increased resistance. Hence, the quantity of current that is sent back to the gauge decreases.

* The gauge
* Current from the sending unit passes through a resistor that either wraps or is located close to the bimetallic strip.
* A bimetallic strip is a piece of metal made of two different types of metals. The metals have their own rate of thermal expansion.
* When the strip gets heated, one metal expands less than the other which results in the formation of curve on the strip. The bending action of the strip helps in movement of the needle.

* Microprocessor-controlled gauges
* Latest automobiles have a microprocessor which reads the variable resistor in the fuel tank and sends the information to other microprocessors in the dashboard.
* Microprocessor provides some damping to the needle movement, for example, while taking a turn or up a hill, the fuel movement is irregular in the fuel tank. In this situation, if a needle was quick to respond to the changes, it might be bouncing in the fuel tank. When a microprocessor is used, the software calculates the average of the float positions.

Types of fuel gauges
* Thermostatic fuel gauge, self-regulating
* In this type of fuel gauge a bimetallic strip is linked to the pointer. The deflection of the bimetallic strip results in the movement of the needle.
* The arm controls the movement of grounded point which makes contact with another point which makes a contact with bimetallic strip.

Thermostatic fuel gauge, external regulating
* This type of fuel gauge uses an external voltage limiting unit with a variable resistance fuel tank sending unit.
* Power supplied to the gauge is maintained constant with the use of a voltage limiter.

Thermostatic fuel gauge, differential gauge
* It is similar to the other types of fuel gauges, but uses two electrically heated bimetallic strips.
* The position of the pointer is obtained by dividing the voltage between these two strips.

Magnetic fuel gauge
* Magnetic fuel gauge has a pointer mounted on the armature. The movement of the gauge is influenced by the magnetic field that is created by two separate magnetic coils contained in the gauge.
* The strength of the variable magnetic field is determined by the rheostat.

Importance of fuel gauge
* Fuel gauge offers a good assessment of the amount of fuel in your fuel tank.
* Either way, engine gauges are the first line of defense against expensive repairs. They also help to extend the life of your engine, get better fuel economy and improve your speed too.
* When replacing or adding gauges, the size of your dashboard and other openings are going to precept some of your choices.

There may be different types of fuel gauges and each represents the same quantity i.e. quantity of fuel present in the tank. The difference lies in the accuracy and sensitivity of the gauge.

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