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Fuel level sensors vs fuel flowmeters

Wed Sep 06, 2017 10:21 am

I'll start with the working principle of the devices, and then I will indicate the reasons for using this or that type of sensor.

The fuel level sensor
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All this information is true for all fuel level sensors of any manufacturers.

Type - capacitive.

The measuring part, which is situated in the tank, is actually a capacitor whose capacity varies depending on the fuel level. The value of this capacitance is measured and converted further in the form of signals (analog, frequency or digit).

The measurement principle itself imposes a number of limitations and has its pros and cons.

This method allows you to control accurately the level of fuel in the tank, BUT! under ideal conditions - a tank should be of the correct geometric shape and there should be the absence of disturbances in the mirror surface of the fuel.

But unfortunately in real life there are no ideal conditions and such factors as the unevenness of the road surface, acceleration / slowdowning, long lifting movement/ down coming, holes, etc. are strongly affected the fuel level sensor’ work.

According to that, there are fluctuations in the fuel in the tank. The problem of these fluctuations (on the chart it looks like false fillings / drainings) the different manufacturers of fuel level sensors and software solve by applying different filters. But the stronger the filter, the less precise the fuel control is (for example, the filter can smooth the sharp drop of 5 liters - this parameter is adjustable).
It is the inevitability of false fillings/ drainings that makes it impossible to determine the exact fuel consumption with the help of fuel level sensor.

The fuel level sensor controls the fuel tank, that excludes the frauds with checks (for example, when a driver on a route buys low-quality fuel, but brings a check from the most expensive fuel station in the region).

The value of the fuel consumption by contrast is a calculated value and depends heavily on the settings of the device itself, as well as on the operating conditions, the manner of driving, etc.

Also against the fuel level sensors, drivers invented many ways to deceive him.

Examples and recommendations:

The most common is the drain through the return line. In that case the draining is carried out in a separate container in motion and with a low flow rate. And that is impossible to detect on chart. When installing fuel level sensors, fuel pipes are not sealed and not controlled. For example, with an increase in fuel consumption from 25 l / h to 30 l / h (on the chart this will not be seen), it could be drained 5 l / h (for a shift it is about 5 * 8 = 40 liters per day)/

Besides there are other ways also:
1. Draining during refueling
2. The air ball in the tank
3. Alcohol (or oil refining products) into fuel. The physical properties of the fuel change.
4. "Blowing" the tank
5. And others.

Accordingly, to identify discrepancies and deviations, it is necessary to keep a large staff of analysts who will view the schedules of each vehicle, compare periods, filter values, and draw conclusions about the presence / absence of manipulation with fuel. This works only for fleets where there is a low number of vehicles.
And it is extremely difficult to automate the process of fuel consumption monitoring.

Summarizing the above:
The determination of fuel consumption by fuel level sensor is not rational, because:
1. Indirect, but calculated method of measurement
2. Strong dependence on operating conditions.
3. The need for manual control. The cost of time for the analyst negates the benefits of implementation.
4. If there is a rough filtration – it will be a decrease of control.
5. There is no control when there are several consumers from one tank

The fuel level sensor should be used to monitor the tank - for example, to track the places of refuelings and compare them with checks, but not for fuel consumption control.

In the development of our fuel level sensor Eurosens Dominator, we applied the principle of modular design that allows:
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1. Maximize the protection of the most expensive part of the fuel level sensor
2. Ensure the ease of diagnosis
3. Reduce maintenance and operation costs
4. Provides an opportunity with minimum costs (no need to purchase a new one) to reinstall the level sensor from one vehicle to another (after decommissioning the vehicle, for example)
Along with this, the most common fault is the cable breakage

In our design, it is enough to replace the cable, but you do not need to purchase a new sensor.

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The fuel flowmeter is a device that measures the amount of fuel directly in the fuel line.
The principle of measurement is the "ring in the ring"

The data on the instantaneous fuel consumption is transferred to the monitoring system.

Ideal device for determining the fuel consumption, because:
1. Direct measurement method.
2. It does not depend on the operating conditions. Is not afraid of fluctuations, acceleration / slowdowning, etc.
3. The absence of false events allows you to automate the process of determining the actual fuel consumption.
4. If properly installed and sealed, the intervention in the system is completely excluded – IT IS NOT POSSIBLE TO CHEAT ! Since all connections between the consumer (motor) and the sensor are sealed. The insertion is excluded.
5. It does not depend on the changes in the composition of the fuel and its dialectic permeability.
6. Allows you to control the operating modes of the machine (idle, normal operation, overload). For example, you can estimate how much the car is idling for a shift.
7. Control additional consumers (refrigerator) with great accuracy.

Cons - lack of tank control. There is no information about places of refuelings and comparisons with checks.

When choosing a flowmeter, it is necessary to pay attention to the following features:
1. If the circuit on the reed switch is used to remove the signal from the camera, it may be stopped by a magnet. The signal should be taken by the Hall sensor.
2. Mandatory function - the presence of thermal compensation. Temperature sensors should be on each chamber of the flowmeter.
3. Obligatory function - program filtration of water hammers. The use of a non-return valve in the circuit can lead to failure of the injection pump.

In our flowmeters all these and also many other functions are implemented!

Video on stopping the sensor magnet on the reed switch, as well as the possibility of its "wrapping"
Https:// - stop fuel flowmeter on a reed switch with a magnet ( Direct is the name of our flowmeter)
Https:// - the effect of a magnet on the operation of a diesel engine
Https:// - the effect of the magnet on the movement of the ring

It cannot be done on Hall sensors, that we use in manufacturing of our fuel flowmeters – Eurosens Direct (one-chamber) and Delta ( two chambers).

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