GPS tracking systems with fuel consumption monitoring are widely used nowadays and sure can be named as effective innovations
Our experience main requirements for fuel consumption monitoring solutions:
1.    Reliability : fuel monitoring system must work 24h/day without bugs 
2.    Confidence : Results of fuel monitoring (reports) must be clear and provide proven data for customer.

Most of GPS tracking providers offer fuel level monitoring option – with installed fuel level sensor in the fuel tank or CAN Bus data.
We think that there must be a selective approach.

Nuances of fuel monitoring systems on agriculture tractors and special machinery:

A. Fuel tanks have irregular, non-symmetric  shape
А.1  Fuel tank of Amkodor loader

Let us give some advices.

Fuel flow meters can be single-chamber or differential (dual chambers).

Differential fuel flow meters:

Single-chamber fuel flow meters:

Differential flow meters can measure both supply and return flow. To install single-chamber flow meter on diesel engine you need to change fuel supply system. Only fuel consumption flow rate must pass via single-chamber flow meter, without return flow.

Here is a typical scheme of differential flow meter installation:

https://www.massflow-online.com/cms/wp- … Manual.pdf

There is no serious changes in fuel supply system. Fuel flow meter chamber flow resistance is low.   Nothing to worry about. But according to this scheme you need to install 2 non-return valves (check valves) – in each chamber of fuel meter. These valves usually open with pressure 0.25 Bar approx.
On big fuel flows these valves also add its hydraulic resistance. If bypass valve of engine opens at 1 Bar (sometimes even at 0.5 Bar), with check valves fuel pressure in supply channel is growing. And Low pressure fuel pump constantly works under higher pressure. Check valves also have a tendency to stuck.
Check valves are needed for flow meters based on reed switch sensor. Meter can see only one reed switch pulse per chamber rotation, so can’t detect its direction. Due to possible back-flow in fuel lines we need to install these check valves.

In Eurosens Delta we use several Hall effect sensors, per 1 measure chamber turn we receive 3 pulses. With this innovation we can detect direction of fuel flow and no need in check valves.
So, you can install only Eurosens Delta flow meter that have no any affect to fuel supply system.

Second issue with flow meter it is freezing of the fuel inside flow meter chambers in winter.

From installation scheme we can see that the measuring chambers are installed after the fuel fine filter, and through them a large flow of fuel is passing.

If the fuel is liquid enough to pass through the filter of thin clearing of fuel - it will pass through flow meter too. Perhaps short-term pause in flow meter operation is possible during cold start of engine at winter, but a large flow of heated fuel warms up quickly the camera, and the meter start to work.
Another weak point during winter operation is built-in small petrol filters used by several flow meter manufacturers. They are not suitable for diesel fuel. Their main function is to protect measuring chamber from dirt during installation. In the future, they become a potential weak point and place of fuel thickening at winter.
Eurosens flow meters don’t have such built-in filters, we recommend to use an extra external fuel filter by proper quality and volume.

Resume:
No any reasons to be afraid of Eurosens Delta fuel meters.
No any engine or fuel meter problems during everyday operation.

Now we will speak about single chamber flow meter installation.
Usually single chamber flow meter is installed like this:

Conditions of high-pressure pump operation are changed:
1.    High-pressure pump is not cooling anymore by passing fuel flow
2.    Fuel tank is heating with less, because return fuel flow after fine fuel filter is cooler compared to return fuel flow from high pressure fuel pump (before modification).

In general, this scheme is OK, but sometimes you can face problems.
On this scheme we can see again non-return valve (check valve). It can create problems:
1.    This valve can stuck
2.    If bypass valve begins to operate with lower pressure and its pressure can be compared with check valve opening pressure – high pressure pump will be short of fuel. All fuel will return in tank without coming to high pressure pump. Engine will lost power.
3.    This check valve makes high pressure pump section completely isolate from bypass valve. It may cause hydroblows and immersion of fuel to lubrication system

So, we can recommend single-chamber Eurosens Direct PN fuel flow meter, equipped with Hall-effect sensors. Installation of non-return valve is not needed.  It simplifies fuel system and hydroblows are avoided, because all parts of fuel supply system are connected to bypass valve.

Eurosens Direct also has bigger metering chamber volume that increases operation life and adds some immunity to high viscous fractions of fuel  (at winter).
                                        DFM100(90, 50), VZP4          - 5000 mm3.
                                        Eurosens Direct PN100          -10000 mm3

Resume

Single chamber flow meters you can be used when:
1. Diesel engine is low-boosted, not equipped by electronic systems. Operation mode of high-pressure fuel pump will be changed.

2. There are no problems with high-viscous fractions of fuel in winter.
3. You want to save a little money (compared to differential flow meter).

We hope that our advices will help to make right choice and save a lot of money with help of precise and simple real-time fuel monitoring device: fuel flow meters.

Every flow meter is calibrated at factory in whole operation range (shown in passport). Calibration data are stored in flow meter
Some diesel engines have high flow rates in supply and return line and low fuel consumption. For example : Supply fuel rate 200 Liters/hour, return fuel rate - 197 Liters/hour and resulted fuel consumption is only 3 Liter/hour - during Idling.

In such cases precision of factory settings may be not enough. Adaptation for given engine is required.
You can modify calibration using this manual

There are several ways to do it

"Refueling" method:
1. Refill fuel tank for max, till visible level of fuel.
2. Leave vehicle to perform its usual operations to consume at least 1/2 of tank.
3. After it make refueling till max and visible level of fuel in tank again and measure volume of refueling.
4. Compare volume of refueling with consumed fuel volume by flow meter.

Use special deaerator device from Mechatronica in this case.

Direct and Delta flow meters detect current operation mode based on these thresholds
Current mode  is applied till instant fuel consumption (per hour) still lower than threshold (subtractive consumption for Delta).

For example for this values

3 Liters per hour - Idle
10 Liters per hour - Nominal
40 Liters per hour - Nominal
55 Liters per hour - Overload
105 Liters per hour - Someone cheating flow meter

Volume of fluid equal to the inner volume of the measuring chamber is pushed out during the full single turn of the ring. Eurosens electronics generates one output impulse at the same time.
The flow sensor measures the amount of fuel flowing through the measuring chamber. Pressurized fluid entering through the inlet nozzle flow sensor in the inlet of the measuring chamber, the piston slides along the inner surface of the chamber and simultaneously slides along the jumper. The piston displaces fluid enclosed in it inside and outside of the piston chamber through its outlet to the outlet port.
The enclosure provides the orientation of the axes of rotation of the cover pin with the magnets and the hub of the piston, thanks to the number of dimensions of the cover and the housing which provides the optimum rotation of the ring chamber.
During one revolution of the piston displaced by the volume of liquid equal to the volume chamber. In this case, the electronic position sensors generate pulses as the turnover of the piston, which are transmitted to the electronic control unit for the selected interface.

Flow consumption signal from Direct P, Direct PN and Delta PN is just usual pulses. You need to count pulses right. Weight of pulse (in milliliters) is shown in device passport.
For Eurosens Direct P - each flow meter has own weight of pulse, according to manufacturer's benchmart  after assembly.

For Eurosens Direct PN and Delta PN it is constant:
for 100 serie - 0.005 liter
for 250 serie - 0.01 liter
for 500 serie - 0.02 liter

Some cheap GPS trackers can't perform with flow meters it well because don't have internal timer and rely only for GPS receiver for time information. That means that if no GPS signal - pulses can be not registered and measurement will be wrong.

1. Decide single chamber flow meter or differential (two chambers).
Most of diesel engines have supply and return line.
So, you need either measure fuel flow in both lines or modify fuel system in such manner, so there is only supply flow must be measured.

Easiest way - measure supply and return flow with Eurosens Delta flow meters. Eurosens Delta calculates total consumption based on supply and return flow.

If you want to save a little money - you can modify fuel system and install Eurosens Direct.

How to modify fuel system - look here:

It is important that modification of fuel system in such manner can affect operation of engine, expecially when engine have modern design (Common-rail, many electronic sensors).
We can recommend to do this modification only if:
1. Engine is not performing under maximum load
2. Engine is Euro-2  or older. Don't have a lot electronic sensors which can detect error
3. You have enough experience and knowledge in diesel engine operation and design.

Can be installed on engines or boilers without return line, or with fuel feed system modification.

Modifications:
Eurosens Direct PN 100
Eurosens Direct PN 100 I
Eurosens Direct PN 250
Eurosens Direct PN 250 I
Eurosens Direct PN 500
Eurosens Direct PN 500 I
Eurosens Direct P 100
Eurosens Direct P 250
Eurosens Direct P 500

Meaning of letters:

P - simpliest electronic scheme inside, with reed switch. During manufacturing, every fuel meter is calibrated on different fuel flows. for P-models we calculate total coefficient as compromise, it corresponds usually middle values of fuel flow in flow meter range.
This coefficient is shown in each device passport.
PN - fuel flow meter has powerful STM32 processor inside. PN flowmeters have some advantages over P-serie:
1. Calibration table is not used for compromised coefficient calculation but recorded in non-volatile memory of flow meter. And calibration coefficients are applied in real-time. So, PN-flow meter always have same weight of pulse (normalized output).
Also precision of measurement is better (1% error instead of 2%).
2. Instead of reed switches - Hall effect sensors are used.
3. Sensor can detect external intervention in operation and store this fact in memory
4. PN meter can provide not only fuel consumption but some other parameters : operation time of diesel, fuel consumption in different operation modes (idle, normal load, overload, external intervention) and time of operation in these modes. This information is available via RS232/RS485 interface  - Direct PN(RS), or via K-line in Direct PN.
5. Temperature sensor and temperature compensation.

I - means built-in display.
You can select a parameter to display by special key.
Display option is available only in PN-line.