Best sensors for measuring fuel flow rate in vehicles

There are many ways to measure flow rate. Accurate flow rate measurement may require a positive displacement flow sensor, but they aren't usually cheap. Flow can be measured at the fuel injectors as well. Usually you can just tap into the OBD2 system to extract fuel data, because every car these days has fuel measurement already implemented. It is unlikely that a low-cost external measurement system will perform better. There also questions about safety that affect the answer. More information about your application is needed to give a better answer.

1) This device is to address short-fueling.(Yes, short-fuelling is a problem in many countries).
Not connecting with fuel pipe but fit around the tank's fuel cap so that when the vehicle is refueled, it notifies the actual volume amount going in the vehicle.

2) This is not the best sensor but to start with but can be used with fuels. e.g. similar plastic sensors for diesel. www.amazon.in/.../B093ZNNY84 . Planning to move to other sensors as we progress. If you know any better compact, cost efective,accurate sensors that can do the job, please do share.

3) Which is the simple, compact, cost effecient way to get refueling volume displayed to the users? On a seperate device or on a app or send a notification on SMS/Whatsapp? Please help share more in detail on devices available for each option & how it can be achieved?

"but fit around the tank's fuel cap".

Surely there's just the tiniest risk, maybe I'm blowing it out of proportion (but I don't think so) that this isn't the best idea, to put dodgy Amazon hardware or your DIY circuitry around the whole general fuel area?

What's the benefit anyway. Will you argue with the fuel station that this cheap project is more accurate than their dispensing systems which might cost a thousand times more? Where will that get you?

shabaz To make an informed decision & customer awareness. I repeat, yes short fueling is an issue in many countries. This is an open design research project & so progress. Not just with close minds.

As I said in your other thread - this flow meter is not very accurate. In reality, the accuracy is usually around 10-15%, even if such "manufacturers" claim 1% it will be under best conditions (i.e. calibrated against an external reference, at a fixed flow rate). Where the flow rate is not consistent, the result will be wrong by quite a bit - below the minimum flow rate, it won't register AT ALL or will do so inconsistently.

Fuel is tricky - its volume often changes quite a bit with temperature and proper fuel pumps compensate for change in density due to temperature. Such a sensor will not natively compensate.

You may be better off filling your own fixed-volume jerry cans of known volume and transferring that to your own tank. Or just fill a can and weigh it. It seems quite a bit safer and simpler ...

- Gough

Im sorry to say it's not informed. It will be very uninformed because the user will be completely deluded if he/she thinks its accurate (or safe!). 

Im sorry to say it's not informed. It will be very uninformed because the user will be completely deluded if he/she thinks its accurate (or safe!). 

Sorry but i'm looking for inputs towards a resolution. Happy to take them but not interested Nay's & neighs during RnD

How would it even work? if the design is a ring around the fuel cap, how will the nozzle fit in it, to meter the flow, while at the same time fitting into the car? The fuel station isn't going to reduce the nozzle diameter or size just for your car. If they did that, then it wouldn't be suitable for other cars. They would have to dedicate that fuel pump for just you. I can't see them doing that but surely even you see that it is a bit of a stretch!
Otherwise, if it sticks out, then how will it detach, and how will the user remove the fuel remnants on it between each use?

All the above is by way of suggesting that it doesn't seem feasible. Is this a school project? Even then I can't see it flying for coursework. No one would realistically think any of this is feasible, in terms of safety or practicality or accuracy!

I like your negativity & not thinking from the resolution perspective. Some time it bois down to personality!

I answered you a while ago in your other thread (it's a bit confusing when you have two on the same topic.)

You probably won't like my answer any better:

A flow sensor capable of giving accurate measurements of the amounf of fuel pumped into a motor vehicle during re-fueling would have to be the same bore as the existing fuel filler and be installed properly in line with it. This would have to meet stringent regulatory requirements for safetey (especially in petrol powered vehicles). seperate approval would be needed for every vehicle type.

I don't know of an off the shelf flow sensor that would work as the core of the design.

I can't see the cost being less than a few hundred pounds/dollars per vehicle even if the product were made in reasonable numbers.

What it boils down to is that your problem (checking amount of fuel delivered into a vehicle) can't reasonably be addressed with a flow sensor of any known type.

This means that you will need to step back and look at other solutions to the problem, or invent a completely new kind of flow sensor.

MK

michaelkellett  Thanks, your inputs are valuable. Agree & we are trying to figure out the complexity & cost-efficiency towards the resolution which is why reached out to this learned community for the inputs   

I'm guessing that the idea is that you would take something like this:

https://www.amazon.in/MagiDeal-Gasoline-Delivery-Dispenser-Electronic/dp/B07JRFSPVD/ref=sr_1_10

which already has that flow meter built into a trigger nozzle, then somehow stick the pump delivery nozzle snuggly into the back of that in such a way it forms a perfect seal and pumps the fuel at a steady rate through the meter and then into a normal petrol tank receptacle.

However, there normally is a venturi tube in the pump delivery nozzle, which would have to be routed separately to the end of the nozzle with the flow meter in order for the delivery nozzle to open its dispensing valve. The position and size of this venturi tube probably varies widely from nozzle to nozzle.

You then have to scale that down in such a way that the scammer doesn't notice it attached to the car and request that you remove it before they will deliver fuel and scam you.

In theory you could insert the flow meter into the filler pipe out of view with a remote display but that would then require modifying a wide range of vehicle types and probably void any warranty / insurance in the process.

@beacon_dave 

Thanks, your inputs are valuable. Accuracy +-1% is what I'm aiming.  To start with, I agree, I'm using low cost flow rate sensor but how true it is that the overall Turbine flow rate sensors have accuracy of more than +-5% as claimed by many above. If so, how come devices like this or this are commercially viable? All i'm trying to do is make the product cheaper & for end users which makes it a buyable product rather than fitting it in the trigger nozzle. 

What is the purpose of venturi tube. Is it to measure flow or just to maintain a steady rate?If it is just to maintain the steady rate, then e.g. 'A device like a fuel tank cap which measures and displys the readings of fuel volume pumped'. The fuel getting flown from the nozzle with the venturi tube to this device is already flowing at a steady rate, so why we would need it?  

I didn't understand the point why it needs to be hidden from the scammer? The fuel pumps have the liability to give what is paid & all this device is going to do is to give an assurance that there is no short-changed. 

The original water flow meter you linked to appeared to have an accuracy of +/-3% and as previously suggested that will likely be under ideal conditions e.g. at a certain installed angle and at a certain flow rate. That will be still be viable for many applications.

I think that petrol pumps tend to use a piston type flow meter rather than a turbine arrangement and they will also likely be well matched to the flow rate of the pump passing the liquid through them. They are likely to be serviced and calibrated at regular intervals as well.

Hence why I was wondering about the accuracy necessary to make it viable over say the existing fuel gauge. At what point do you challenge the reading on the pump.

If you doubt the advice given about accuracy, then perhaps do some experiments with some of the cheaper flow meters and see what accuracy you can achieve under different conditions. Perhaps also get a piston flow meter from an old decommissioned petrol pump and try that for comparison.

The venturi tube controls the trigger mechanism in the petrol pump nozzle. It shuts off the pump when the tank is full or if you get blow-back.or if the tank's venting is faulty. It's a simple principle but the design is quite intricate. If your design attempts to couple a petrol pump nozzle directly into the input of a flow meter, you may find it affects the functioning of the venturi tube and shuts off the pump in the process. Some tubes vent to the outside of the nozzle through a small hole, others are contained inside of the nozzle itself so any design needs to accommodate the different types. 

A scammer wants to make money so if they see such a device fitted then they may not want to serve you and wave you on so as they can scam the next person. Others may think it simply looks like a suspicious device and refuse to serve you. Depends on the type of petrol station it is though - attendant at the pump, self-serve but pay the attendant in the exit booth, or self-serve, pay with card at the pump. If it is hidden from view, then you avoid these sorts of scenarios.

Have you got any conceptual sketches of what the new fuel cap might look like ?

Fuel caps tend to vary between cars and not only that but the recess/access flap they are fitted into/behind tends to vary as well. Hence why pump nozzles tend to be the design that they are, to reach into awkward places.

Coupling onto the car's fuel tank filler pipe with a good seal might get you a more compact device but then it might not be so universal.

If the idea is to be able to pass the pump nozzle through the fuel cap and into the existing filler pipe, then that means that the flow sensor will somehow have to end up inside the car's filler pipe. Perhaps spring-loaded so the end of the nozzle pushes it out of the cap into the filler pipe and then retracts it back into the cap after removing the pump nozzle. Otherwise the new cap requires its own filler pipe  

If you want to keep it universal, then you are probably going to have to cut the end off a standard pump nozzle, cut the end of the filler pipe off a standard petrol tank and then insert the flow meter between the two sections. The nozzle end fits into the petrol tank filler pipe and the pump nozzle fits into the filler pipe end, with the flow meter and display in some sort of housing the middle.